Neuropsychopharmacology (2005) 30, 1312–1323
& 2005 Nature Publishing Group All rights reserved 0893-133X/05 $30.00
www.neuropsychopharmacology.org
Elevation of Ambient Room Temperature has Differential
Effects on MDMA-Induced 5-HT and Dopamine Release
in Striatum and Nucleus Accumbens of Rats
Esther O’Shea1, Isabel Escobedo1, Laura Orio1, Veronica Sanchez1, Miguel Navarro2, A Richard Green3 and
M Isabel Colado*,1
1
Departamento de Farmacologia, Facultad de Medicina, Universidad Complutense, Madrid, Spain; 2Departamento de Psicobiologia, Facultad de
Psicologia, Universidad Complutense, Madrid, Spain; 3Pharmacology Research Group, School of Pharmacy, De Montfort University, Leicester, UK
3,4-Methylenedioxymethamphetamine (MDMA) produces acute dopamine and 5-HT release in rat brain and a hyperthermic response,
which is dependent on the ambient room temperature in which the animal is housed. We examined the effect of ambient room
temperature (20 and 301C) on MDMA-induced dopamine and 5-HT efflux in the striatum and shell of nucleus accumbens (NAc) of
freely moving rats by using microdialysis. Locomotor activity and rectal temperature were also evaluated. In the NAc, MDMA (2.5 or
5 mg/kg, i.p.) produced a substantial increase in extracellular dopamine, which was more marked at 301C. 5-HT release was also
increased by MDMA given at 301C. In contrast, MDMA-induced extracellular dopamine and 5-HT increases in the striatum were
unaffected by ambient temperature. At 201C room temperature, MDMA did not modify the rectal temperature but at 301C it produced
a rapid and sustained hyperthermia. MDMA at 201C room temperature produced a two-fold increase in activity compared with salinetreated controls. The MDMA-induced increase in locomotor activity was more marked at 301C due to a decrease in the activity of the
saline-treated controls at this high ambient temperature. These results show that high ambient temperature enhances MDMA-induced
locomotor activity and monoamine release in the shell of NAc, a region involved in the incentive motivational properties of drugs of
abuse, and suggest that the rewarding effects of MDMA may be more pronounced at high ambient temperature.
Neuropsychopharmacology (2005) 30, 1312–1323, advance online publication, 9 February 2005; doi:10.1038/sj.npp.1300673
Keywords: MDMA; dopamine; 5-HT; nucleus accumbens; locomotor activity; room and rectal temperature
3,4-Methylenedioxymethamphetamine (MDMA or ‘ecstasy’)
is a commonly used recreational drug, often ingested at
crowded and warm dance clubs and raves. The main
adverse effect related to acute MDMA toxicity is hyperthermia, with body temperatures as high as 431C having
been reported (Henry, 1992). The hyperthermic response
is responsible for most of the deaths caused by the
drug since many of the other toxicological problems that
are seen, particularly rhabdomyolysis, disseminated intravenous coagulation, and acute renal failure (Brown
and Osterloh, 1987; Henry et al, 1992; Screaton et al,
1992) result from hyperthermia. Hyperthermia is also
observed in experimental animals immediately after drug
*Correspondence: Professor MI Colado, Departamento de Farmacologia, Facultad de Medicina, Universidad Complutense, Madrid 28040,
Spain, Tel: þ 34 91 394 1213, Fax: þ 34 91 394 1463,
E-mail: colado@med.ucm.es
Received 17 March 2004; revised 3 November 2004; accepted 1
December 2004
Online publication: 17 December 2004 at http://www.acnp.org/citations/
Npp121704040123/default.pdf
injection and its magnitude is very dependent on ambient
room temperature during drug exposure (eg Green et al,
2004).
Systemic MDMA administration has also been shown to
increase extracellular dopamine and 5-HT levels in mesolimbic brain areas such as the nucleus accumbens (NAc)
(Yamamoto and Spanos, 1988; Marona-Lewicka et al, 1996;
Kankaanpaa et al, 1998). The NAc is a brain area that is
responsible for the incentive motivational properties of
most drugs of abuse and the rewarding effects of MDMA
have been shown using the appropriate paradigms. Thus,
rats treated with MDMA developed a positive and dosedependent response in the conditioned place preference
(CPP) test (Marona-Lewicka et al, 1996; Bilsky et al, 1991;
Bilsky and Reid, 1991; Schechter, 1991). Since CPP is
believed to be a measure of appetitive behavior where the
animal associates contextual cues with either a positive or
negative feeling produced by the drug, these results provide
direct evidence of the rewarding properties of MDMA in
rats. A rewarding effect of MDMA has also been shown in
the self-stimulation paradigm in rats (Hubner et al, 1988),
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1313
where MDMA lowers the reward threshold of electrical
stimulation, and in the drug self-administration test in rats
(Schenk et al, 2003; Daniela et al, 2004) and baboons (Lamb
and Griffiths, 1987). The locomotor hyperactivity observed
after MDMA injection is also consistent with this drug
exerting a positive rewarding effect (Gold and Koob, 1988;
Gold et al, 1989a). 6-Hydroxydopamine lesions of the NAc
attenuated the locomotor response produced by MDMA
(Gold et al, 1989b), and dopaminergic activity thus appears
to be selectively responsible for MDMA- and amphetamineinduced locomotor activity, since blockade of dopamine
receptors or 6-OHDA lesions of mesolimbic dopamine
fibers did not block caffeine, scopolamine, heroin, or
corticotrophin-releasing factor-induced locomotor activation (Swerdlow and Koob, 1985; Vaccarino et al, 1986). On
the other hand, the fact that 6-OHDA lesions of the NAc
attenuated, but did not abolish, the MDMA-induced
hyperactivity (Gold et al, 1989b) indicates that the
MDMA-induced dopamine release in the NAc is not the
sole cause of the rewarding effects of MDMA and there is
some evidence that serotoninergic activity may also be
involved.
Recently, it was shown that an elevation of ambient room
temperature enhanced the prosocial effects of MDMA and
the number of MDMA infusions self-administered by rats
(Cornish et al, 2003). This suggests that the rewarding
effects of MDMA are more pronounced at high ambient
temperature and that the enthusiasm of recreational users
for consuming the drug in hot environments might not be
coincidental. Nevertheless, it is not known whether the
neurochemical changes related to the rewarding effects of
MDMA are in any way dependent on the ambient room
temperature in which the drug is ingested.
Using in vivo microdialysis, we have now examined the
effect of ambient temperature on MDMA-induced dopamine and 5-HT output and metabolism in the striatum and
in the shell of NAc of freely moving rats. Locomotor activity
and body temperature during drug exposure was also
evaluated at standard (201C) and high (301C) room ambient
temperature.
MATERIALS AND METHODS
Animals and Drug Administration
Male Dark Agouti rats (175–200 g, Interfauna, Barcelona)
were used. They were housed in groups of five, in
conditions of constant temperature (21721C) and a 12 h
light/dark cycle (lights on: 0700), and given free access to
food and water. In order to habituate the animals to the
different ambient temperatures studied, on the day of the
experiment, rats were maintained at an ambient room
temperature between either 19 and 211C (referred to in the
text as 201C) or 30 and 321C (referred to as 301C) for 2.5 h
before MDMA (2.5 or 5 mg/kg, i.p.) administration and
these conditions were maintained for the entire experimental procedure. Rectal temperature data and microdialysate data were obtained from the same animals and
separate animals were used for the locomotor activity
assessment. Animals were only treated at one dose level and
used to study one brain area.
MDMA (NIDA, Research Triangle Park, NC) was
dissolved in saline (0.9% NaCl) and given in a volume of
1 ml/kg. Dose is reported in terms of the base.
All experimental procedures were performed in accordance with the guidelines of the Animal Welfare Committee
of the Complutense University (following DC86/609/EU).
Measurement of Rectal Temperature
Immediately before and up to 5 h after MDMA injection,
temperature was measured every 30 min by use of a digital
readout thermocouple (Type K thermometer, Portec, UK)
with a resolution of70.11C and accuracy of70.21C attached
to a CAC-005 Rodent Sensor, which was inserted 2.5 cm into
the rectum of the rat, the animal being lightly restrained by
holding in the hand. A steady readout was obtained within
10 s of probe insertion.
Measurement of Locomotor Activity
Animals were placed at either ambient room temperature
(20 and 301C) 2.5 h before treatment and this temperature
was maintained for the entire experimental procedure. Rats
were treated with MDMA (5 mg/kg, i.p.) or saline and
immediately placed in a locomotor activity chamber. No
habituation to the chamber was performed. The opaque
plastic chamber measured 35 37 44 cm (w l h) with
eight infrared beams and photocells distributed in two rows
along the length of the chamber. The upper row was raised
10.5 cm from the base of the cage and the lower row 5.5 cm.
Spacing between adjacent beams was 7.5 cm. The locomotor
activity measurement consisted of the total number of
photocell beam breaks (upper and lower beams) recorded
in 30 min analyzed by a personal computer. Counting began
10 min after injection and placement of the animals in the
chamber area.
Implantation of Microdialysis Probe in the NAc and
Striatum
The day before the experiment rats were anaesthetised with
pentobarbitone (Euta-Lender, 40 mg/kg) and secured in a
Kopf stereotaxic frame with the tooth bar at 3.3 mm below
the interaural zero. A guide cannula was implanted in the
right side of the brain according to the following
coordinates: þ 9.4 mm from the interaural line, 1.0 mm
mediolateral, and 5.4 mm below the skull for the NAc, and
þ 7.9 mm from the interaural line, 2.5 mm mediolateral,
and 4.0 mm below the skull for the striatum (König
and Klippel, 1963). Cannulae were secured to the skull
as described by Baldwin et al (1994). On the day of the
experiment, the dialysis probes (membrane length:
2.0 mm 500 mm for the NAc and 4.0 mm 500 mm for
the striatum; CMA/12, Sweden) were inserted in the guide
cannulae such that the membrane protruded its full length
from the end of the probe.
Measurement of Dopamine, 5-HT and Their Metabolites
in the Dialysate
Catechol and indole efflux in the brain in vivo was measured
by the method described in detail by Colado et al (1999).
Neuropsychopharmacology
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1314
At 24 h after implantation, probes were perfused with
artificial cerebrospinal fluid (aCSF; KCl: 2.5 mM; NaCl:
125 mM; MgCl2 6H2O: 1.18 mM; CaCl2 2H2O: 1.26 mM) at
a rate of 1 ml/min and samples collected from the freely
moving animals at 30 min intervals in tubes containing 5 ml
of a solution composed of HClO4 (0.01 M), cysteine (0.2%),
and sodium metabisulfite (0.2%). The first 60 min sample
was discarded and the next three 30 min baseline samples
collected. After injection, samples were collected every
30 min for 5 h.
Dopamine, 5-HT and the metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and
5-hydroxyindole acetic acid (5-HIAA) were measured in
the dialysate by HPLC and electrochemical detection. The
mobile phase consisted of KH2PO4 (0.05 M), octanesulfonic
acid (0.4 mM), EDTA (0.1 mM), and methanol (16%) and
was adjusted to pH 3 with phosphoric acid, filtered and
degassed. The flow rate was 1 ml/min. The HPLC system
consisted of a pump (Waters 510) linked to an automatic
sample injector (Loop 200 ml, Waters 717 plus Autosampler), a stainless-steel reversed-phase column (Spherisorb
ODS2, 5 mm, 150 4.6 mm) with a precolumn and a
coulometric detector (Coulochem II, Esa, USA). The working electrode potential was set at 400 mV with a gain of 1 mA
(for dopamine) and 500 nA (for the remaining compounds).
The current produced was monitored by using integration
software (Unipoint, Gilson).
Measurement of MDMA Concentration in Striatal
Tissue
Brain concentrations of MDMA were determined following
a previously described method with minor modifications
(Sanchez et al, 2001). The striatal tissue was homogenized
in ice-cold sodium carbonate–sodium bicarbonate buffer
(pH 11.5) using an ultrasonicator. The homogenate was
centrifuged at 27 000g for 20 min at 41C. The supernatant
was applied to a 145 mg C8 end-capped SPE light column
(International Sorbent Technology, Waters). The column
was washed with methanol (2 ml) followed by distilled water
(2 ml) before applying the sample (400 ml of supernatant þ
350 ml of distilled water). The column was washed with
water (2 ml) before selective elution of MDMA with
methanol (1 ml).
An aliquot (20 ml) of the resulting eluate was injected
into a Waters HPLC system, which consisted of a pump
(Waters 510) linked to a manual sample injector (Loop
20 ml, Rheodyne), a stainless-steel column (RP 18, 5 mm,
150 4.6 mm, XTerra) fitted with a precolumn (RP 18,
5 mm, 20 3.9 mm, XTerra), and a UV/visible detector
(Waters 2487). The current produced was monitored using
an integrator (Waters M745). The mobile phase consisted of
20 mM potassium dihydrogen phosphate (75%) and acetonitrile (25%), pH 2.5; the flow rate was set to 0.8 ml/min and
UV absorption was measured at 235 nm.
Statistics
Data from the locomotor activity experiments were
analyzed using one-way ANOVA followed by Tukey’s
multiple comparison test where significant differences
occurred. Data from brain MDMA levels were analyzed by
Neuropsychopharmacology
Student’s t-test. Statistical analyses of the temperature
measurements and dialysis were performed using the
statistical computer package BMDP/386 Dynamic (BMDP
Statistical Solutions, Cork, Eire). Data were analyzed by
analysis of variance (ANOVA) with repeated measures
(program 2V) or, where missing values occurred, an
unbalanced repeated measure model (program 5V) was
used. Both used treatment as the between subjects factor
and time as the repeated measure. To evaluate the effect of
ambient temperature, the tests used treatment and ambient
temperature as between subjects factors and time as the
repeated measure. ANOVA was performed on both
pretreatment and post-treatment data. Differences were
considered significant at Po0.05. The results of the
statistical comparisons are included in the figure legends.
RESULTS
Effect of Ambient Temperature on MDMA-Induced
Changes in Rectal Temperature
MDMA (2.5 or 5 mg/kg, i.p.) produced an effect on the
rectal temperature of the rats that was dependent on the
ambient temperature in which the animals were when it was
administered. At an ambient temperature of 201C, MDMA
produced an initial decrease in the rectal temperature of the
animals in the first 30 min (Figure 1). Rectal temperature
then returned to values similar to those found in salinetreated animals by 1 h and remained so for at least 5 h.
However, when administered at an ambient temperature of
301C, MDMA produced a rapid and marked increase in the
rectal temperature of the animals, attaining a peak value of
0.9 or 1.31C above the saline controls in the first 30–60 min
and remaining elevated above controls for 2.5 or 3.5 h (for
2.5 or 5 mg/kg, respectively) (Figure 1).
Effect of Ambient Temperature on MDMA-Induced
Changes in Locomotor Activity
When MDMA (5 mg/kg, i.p. ) was given to rats housed at
201C, it doubled the locomotor activity measured in a
30 min period starting 10 min after treatment compared
with activity measured in saline-injected rats (Figure 2).
Animals housed at 301C and treated with saline showed a
40% reduction in mean activity compared with salinetreated rats at an ambient temperature of 201C, although
this difference was not significant. MDMA given at high
ambient temperature produced a five-fold increase in
activity compared with the saline-treated controls at the
same ambient temperature; however, their absolute activity
was similar to that seen in MDMA-treated rats given the
same dose of drug at 201C.
Effect of Ambient Temperature on the MDMA-Induced
Changes in Monoamine Release and Metabolism in NAc
and Striatum
Dopamine and metabolites in NAc. Administration of
MDMA to rats housed at 201C produced a slight increase
(2.5 mg/kg, i.p.; Figure 3a) or a substantial and rapid
increase (5 mg/kg, i.p.; Figure 3b) of the extracellular
concentration of dopamine, peaking 60 min after injection
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1315
MDMA 2.5 mg/kg
2000
40.5
Saline
MDMA
Photocell beam breaks
Rectal temp. (°C)
40.0
39.5
39.0
38.5
1500
∗
∗∗
1000
500
38.0
0
37.5
-1
0
1
2
Time (h)
3
4
5
30°C
Figure 2 Locomotor activity of rats injected with MDMA (5 mg/kg, i.p.)
at different ambient temperatures. Animals were maintained at a room
ambient temperature of 20 or 301C for 2.5 h before MDMA injection and
during the entire experimental protocol. Rats were placed in the
locomotor activity chamber immediately after MDMA injection and the
total number of photocell beam breaks was counted for 30 min starting
10 min after placement of animals in the chambers. Each value is the
mean7SEM of six animals. Different from the corresponding saline-treated
group: *Po0.05, **Po0.01.
MDMA 5 mg/kg
40.5
40.0
Rectal temp. (°C)
20°C
39.5
39.0
38.5
38.0
37.5
-1
0
1
2
Time (h)
Saline 20ºC
Saline 30ºC
3
4
5
MDMA 20ºC
MDMA 30ºC
Figure 1 Rectal temperature of rats injected with MDMA (2.5 or 5 mg/
kg, i.p.) at different ambient room temperatures. Animals were maintained
at a room temperature of 20 or 301C for 2.5 h before MDMA injection
and for 5 h after. At 201C, MDMA did not significantly modify rectal
temperature compared with saline-treated animals (main effect of
treatment: F(1, 19) ¼ 0.099, NS, for 2.5 mg/kg and F(1, 24) ¼ 0.0024, NS,
for 5 mg/kg). Nevertheless, when MDMA was given to animals housed at
301C, a pronounced and sustained hyperthermia compared with salinetreated animals was observed (main effect of treatment: F(1, 18) ¼ 3.58,
Po0.05, for 2.5 mg/kg; F(1, 23) ¼ 15.49, Po0.001, for 5 mg/kg). The
interaction of treatment ambient temperature was significant at both
dosing levels for the interval 0.5–3.5 h (for 2.5 mg/kg: F(1, 37) ¼ 5.37,
Po0.05; for 5 mg/kg: F(1, 47) ¼ 13.42, Po0.0001), indicating that the effect
of MDMA was different at the two ambient temperatures. Each value is the
mean7SEM of 8–15 animals.
and lasting 2 h in the case of the higher dose (Figure 3b). At
301C room temperature, the MDMA-induced increase in the
dopamine concentration of the dialysate was greater than
that observed at 201C and the enhanced efflux was evident
for at least 4.5 h after drug injection (Figure 3a, b). The
content of dopamine in the dialysate of the saline-treated
group maintained at 301C was also slightly more pronounced than that found in the saline-treated group
maintained to 201C (Figure 3a, b). The absolute basal
values of dopamine in the dialysates of saline-treated
animals maintained at 301C were similar to those observed
in the group at 201C (Table 1).
Injection of MDMA induced a sustained decrease in the
levels of DOPAC (Figure 3c, d) and HVA (Figure 3e, f) in the
dialysate of animals kept at 201C. Similar effects were
observed at 301C, but the effect on HVA was not significant
at the lower MDMA dose (Figure 3e). There was no
difference in the levels of DOPAC (Figure 3c, d) and HVA
(Figure 3e, f) in the dialysate of saline-treated animals at
either ambient temperature. The absolute basal values of
DOPAC and HVA in the dialysates of saline-treated animals
maintained at 301C were similar to those observed in the
group at 201C (Table 1).
5-HT and 5-HIAA in NAc. Administration of MDMA (2.5.
or 5 mg/kg, i.p.) to rats at 201C produced a modest increase
in the extracellular concentration of 5-HT only at the higher
dose that reached a significant difference vs the corresponding saline group between 0.5 and 2.0 h (Figure 4a, b).
However, when MDMA was given at 301C, there was an
increase in the 5-HT levels in the dialysate peaking 60 min
after injection and lasting for 2–3 h. This effect was
significantly different from that observed at 201C (Figure
4a, b). There was no difference in the levels of 5-HT in the
dialysate of saline-treated animals at either temperature
(Figure 4a, b). The absolute basal values of 5-HT in the
dialysates of saline-treated animals maintained at 301C were
similar to those observed in the group at 201C (Table 1).
Injection of MDMA induced a prolonged decrease in 5HIAA levels in the dialysate of animals at 201C (Figure 4c,
d). When the animals treated with MDMA 5 mg/kg were
maintained at 301C, a biphasic effect was observed, an
initial increase in the extracellular 5-HIAA concentration
was followed by a sustained and significant decrease. The 5HIAA curves at both room temperatures were significantly
different for the interval 0.5–3.5 h (Figure 4d). No such
effect was observed at the lower dose (Figure 4c). There
was no difference in the levels of 5-HIAA in the dialysate
of saline-treated animals kept at either temperature
Neuropsychopharmacology
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1316
a 600
b 600
MDMA 2.5 mg/kg
500
DA (% of baseline)
DA (% of baseline)
500
400
300
200
300
200
100
0
0
0
1
2
Time (h)
3
4
5
c
-1
0
1
2
Time (h)
3
4
5
-1
0
1
2
Time (h)
3
4
5
-1
0
1
2
Time (h)
3
4
5
d
150
DOPAC (% of baseline)
150
DOPAC (% of baseline)
400
100
-1
100
50
0
100
50
0
-1
0
1
2
Time (h)
3
4
5
e
f
150
HVA (% of baseline)
150
HVA (% of baseline)
MDMA 5 mg/kg
100
50
100
50
0
0
-1
0
1
2
Time (h)
3
4
5
Saline 20ºC
MDMA 20ºC
Saline 30ºC
MDMA 30ºC
Figure 3 Changes in the extracellular levels of dopamine (DA; a, b), DOPAC (c, d), and HVA (e, f) in the NAc of rats following administration of MDMA
(2.5 or 5 mg/kg, i.p.) at different ambient temperatures. Rats were maintained at a room temperature of 20 or 301C for 2.5 h before MDMA injection and for
5 h after. At both room temperatures (20 and 301C), MDMA produced an increase in the content of DA compared with saline-treated animals (main effect
of treatment: for 2.5 mg/kg: F(1, 12) ¼ 5.29, Po0.05; F(1, 13) ¼ 8.28, Po0.01, respectively; for 5 mg/kg: F(1, 11) ¼ 9.34, Po0.001; F(1, 8) ¼ 65.02, Po0.001,
respectively) and a decrease in the levels of HVA (main effect of treatment: for 2.5 mg/kg at 201C only: F(1, 14) ¼ 7.93, Po0.01; for 5 mg/kg:
F(1, 10) ¼ 17.99, Po0.001; F(1, 10) ¼ 5.45, Po0.05, respectively), and DOPAC (main effect of treatment: for 2.5 mg: F(1, 13) ¼ 44.02, Po0.001;
F(1, 13) ¼ 10.76, Po0.001, respectively; for 5 mg/kg: F(1, 11) ¼ 39.34, Po0.001; F(1, 10) ¼ 26.54, Po0.001, respectively). The interaction of
treatment ambient temperature was significant for dopamine at both dosing levels (for 2.5 mg/kg: F(1, 25) ¼ 3.41, Po0.05 and for 5 mg/kg:
F(1, 19) ¼ 7.63, Po0.01) indicating that the effect of MDMA was different at the two ambient temperatures. Animals maintained at 301C and injected with
saline showed a modest increase in DA levels compared with those at 201C (main effect of ambient temperature: for (a) F(1,14) ¼ 14.39, Po0.001; for (b)
F(1, 9) ¼ 5.26, Po0.05). Values are expressed as a percentage of the mean of three measurements before drug administration. Each value is the mean7SEM
of 5–9 animals. Basal concentrations in saline-treated rats are shown in Table 1.
(Figure 4c, d). The absolute basal values of 5-HIAA in the
dialysates of saline-treated animals maintained at 301C were
similar to those observed in the group at 201C (Table 1).
Neuropsychopharmacology
Dopamine and metabolites in striatum. Administration of
MDMA (2.5 or 5 mg/kg, i.p.) to rats housed at 201C
produced a substantial and rapid increase of the extra-
Ambient temperature and monoamine release following MDMA
E O’Shea et al
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Table 1 Basal Values for Extracellular Dopamine (DA), 5-HT, and Corresponding Metabolites in Saline-Treated Rats and Statistical
Comparison of the Effect of Temperature
201C
Brain area
NAc
Compound
60 min
30 min
0 min
60 min
30 min
0 min
DA
0.4670.09
0.4870.09
0.3670.06
0.4770.09
0.4170.08
0.4570.17
F(1, 21) ¼ 0.001, P ¼ 0.97
DOPAC
204723
219723
195722
165720
182721
188720
F(1, 23) ¼ 0.90, P ¼ 0.35
F-value
HVA
112712
125715
117714
102711
112712
115712
F(1, 22) ¼ 0.07, P ¼ 0.79
5-HT
0.7070.16
0.5670.08
0.5370.07
0.5770.21
0.5670.20
0.4170.08
F(1, 20) ¼ 0.17, P ¼ 0.66
4975
5275
4875
4974
5274
5375
F(1, 22) ¼ 0.11, P ¼ 0.74
DA
0.6370.07
0.6370.08
0.7070.09
0.5470.06
0.4670.05
0.4770.05
F(1, 21) ¼ 3.21, P ¼ 0.09
DOPAC
338744
399755
435763
279738
361749
440758
F(1, 23) ¼ 0.07, P ¼ 0.79
5-HIAA
Striatum
301C
HVA
296738
339741
375748
254733
313739
390749
F(1, 22) ¼ 0.01, P ¼ 0.92
5-HT
0.6570.08
0.6470.08
0.6170.07
1.0070.15
0.9070.11
0.7670.12
F(1, 22) ¼ 3.54, P ¼ 0.07
10077
10077
111713
123714
131717
F(1, 22) ¼ 2.57, P ¼ 0.12
5-HIAA
9576
Three 30 min baseline samples were collected immediately before injecting MDMA. Values are mean (pg/ml)7SEM of 22–25 animals.
cellular concentration of striatal dopamine, peaking at
60 min and lasting 3–4 h. At 301C, the changes induced by
MDMA on the dialysate dopamine concentration were
similar in magnitude and duration to those observed at
201C (Figure 5a, b). There was no difference in the
extracellular concentration of dopamine of saline-treated
animals kept at either temperature (Figure 5a, b). The
absolute basal values of dopamine in the dialysates of
saline-treated animals maintained at 301C were similar to
those observed in the group at 201C (Table 1).
Injection of MDMA induced a sustained decrease in the
levels of DOPAC (Figure 5c, d) and HVA (Figure 5e, f) in the
striatal dialysate of animals kept at either ambient
temperature. There was no difference in the levels of
DOPAC (Figure 5c, d) or HVA (Figure 5e, f) in the dialysate
of saline-treated animals at either temperature. The absolute
basal values of DOPAC and HVA in the dialysates of salinetreated animals maintained at 301C were similar to those
observed in the group at 201C (Table 1).
5-HT and 5-HIAA in striatum. Administration of MDMA
(2.5 or 5 mg/kg, i.p.) to animals housed at 201C produced a
substantial and rapid increase in the extracellular concentration of 5-HT in the striatum peaking 60 min after
injection and lasting 2–3 h (Figure 6a, b). Similar changes
were seen in animals housed at 301C (Figure 6a, b). There
was no difference in the levels of 5-HT in the dialysate of
saline-treated animals at either temperature (Figure 6a, b).
The absolute basal values of 5-HT in the dialysates of salinetreated animals maintained at 301C were similar to those
observed in the group at 201C (Table 1).
Low-dose MDMA (2.5 mg/kg, i.p.) produced a sustained
decrease in the extracellular levels of 5-HIAA, which was
not modified by an increase in ambient temperature
(Figure 6c). While injection of MDMA at the higher dose
to animals at 201C also induced a sustained decrease in
dialysate 5-HIAA levels, in animals kept at 301C, it induced
a biphasic response consisting of an initial rise followed by
a decrease (Figure 6d). Nevertheless, 5-HIAA curves at both
room temperatures were not significantly different
(Figure 6d). There was no difference in the levels of 5HIAA in the dialysate of saline-treated animals kept at
different temperatures (Figure 6c, d). The absolute basal
values of 5-HIAA in the dialysates of saline-treated animals
maintained at 301C were similar to those observed in the
group at 201C (Table 1).
Effect of Ambient Temperature on Striatal Levels of
MDMA
In order to investigate the possible effect of ambient
temperature on the concentration of MDMA in the brain,
rats were given MDMA (5 mg/kg, i.p.) and killed 1 h later.
This time point was chosen because the cerebral concentration of MDMA normally peaks 60 min after MDMA
injection (Esteban et al, 2001) and it was the time point at
which neurotransmitter release peaked. There were no
differences between the MDMA levels found in the striatum
of rats treated with the drug at 201C (22.973.4 nmol/g
tissue, n ¼ 4) and those treated at 301C (22.670.2 nmol/g
tissue, n ¼ 4).
DISCUSSION
Using intracerebral microdialysis in freely moving rats, this
study has shown that elevation of ambient temperature
enhances the effect induced by low and medium doses of
MDMA on dopamine release in the shell of the NAc but not
in the striatum. The output of 5-HT is also enhanced in the
NAc, but not striatum, by high ambient temperature
conditions.
Although MDMA increased both dopamine and 5-HT
release in the NAc of animals at 301C, the magnitude of the
MDMA effect on extracellular dopamine levels (260 and
Neuropsychopharmacology
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1318
MDMA 2.5 mg/kg
200
100
0
200
100
0
-1
0
1
2
Time (h)
3
4
5
c
-1
0
1
-1
0
1
2
Time (h)
3
4
5
d
150
5-HIAA (% ofbaseline)
150
5-HIAA (% ofbaseline)
MDMA 5 mg/kg
b 300
5-HT(% of baseline)
5-HT(% of baseline)
a 300
100
50
100
50
0
0
-1
0
1
2
Time (h)
3
4
5
Saline 20°C
MDMA 20°C
Saline 30°C
MDMA 30°C
2
Time (h)
3
4
5
Figure 4 Changes in the extracellular levels of 5-HT (a, b) and 5-HIAA (c, d) in the NAc of rats following administration of MDMA (2.5 or 5 mg/kg, i.p.) at
different ambient temperatures. Rats were maintained at a room temperature of 20 or 301C for 2.5 h before MDMA injection and for 5 h after. At 201C
MDMA (5 mg/kg, i.p.) reduced 5-HIAA levels compared with saline-treated animals (main effect of treatment: F(1, 12) ¼ 21.21, Po0.001) and produced a
significant increase in 5-HT concentration vs the corresponding saline from 0.5-2.0 h (main effect of treatment: F(1, 9) ¼ 3.97, Po0.05). At 2.5 mg/kg, MDMA
only reduced 5-HIAA levels (main effect of treatment: F(1, 11) ¼ 30.58, Po0.001). When MDMA was given at 301C, it produced a pronounced and
prolonged increase in 5-HT concentration compared with saline-treated controls (main effect of treatment: for 2.5 mg/kg between 0.5 and 2.0 h:
F(1, 13) ¼ 5.86, Po0.01; for 5 mg/kg between 0.5 and 5 h: F(1, 9) ¼ 18.49, Po0.001). The interaction of treatment ambient temperature was significant for
5-HT at both dosing levels (for 2.5 mg/kg between 0.5 and 2.0 h: F(1, 26) ¼ 4.08, Po0.05; for 5 mg/kg between 0.5 and 5 h: F(1, 18) ¼ 4.24, Po0.05),
indicating that the effect of MDMA was different at the two ambient temperatures. MDMA also produced a reduction in 5-HIAA levels (main effect of
treatment: for 2.5 mg/kg: F(1, 8) ¼ 8.51, Po0.01; for 5 mg/kg: F(1, 8) ¼ 6.06, Po0.01). The interaction of treatment ambient temperature was not
significant for 5-HIAA at either dosing level (for 2.5 mg/kg: F(1, 19) ¼ 0.00, NS; for 5 mg/kg: F(1, 20) ¼ 2.27, NS), indicating that the effect of MDMA was the
same at the two ambient temperatures, excepting for the interval 0.5–3.5 h at the higher dose (F(1, 20) ¼ 3.80, Po0.05). Values are expressed as a
percentage of the mean of three measurements before drug administration. Each value is the mean7SEM of 5–8 animals. Basal concentrations in salinetreated rats are shown in Table 1.
490% increase for 2.5 and 5 mg/kg at 201C) was larger than
that elicited on 5-HT concentration (197 and 265%). This
more pronounced effect of MDMA on dopamine release is
not a consequence of the high ambient temperature since
White et al (1994) observed a similar difference at standard
room temperature. Nor can the difference in increases in
the levels of DA and 5-HT in the NAc following MDMA be
attributed to a different affinity of MDMA for monoamine
transporters or to its different potency for inducing [3H]DA or [3H]-5-HT release in vitro. Using hippocampal and
striatal synaptosomal preparations, it has been shown that
MDMA is only slightly more potent at inhibiting [3H]-5-HT
than [3H]-dopamine uptake (1.7 and 3.2 times, in each area,
respectively) and that it is 10 times more potent at
increasing [3H]-5-HT than [3H]-dopamine release (Crespi
Neuropsychopharmacology
et al, 1997). Nevertheless, in NAc, there is a greater density
of dopamine than 5-HT terminals and this morphologic
difference may account for the relatively larger MDMAinduced increase in extracellular dopamine levels compared
with 5-HT (Dewar et al, 1991; Mennicken et al, 1992). In
addition, although 5-HT axon density is higher in the shell
of NAc than in the dorsal striatum (Deutch and Cameron,
1992) few axons in the area express 5-HT transporters. It is
worth mentioning that MDMA penetrates into 5-HT nerve
terminals by means of 5-HT uptake system (Sanchez et al,
2004) and increases 5-HT release through the 5-HT
transporter operating in reverse (Rudnick and Wall, 1992).
In addition to increasing dopamine release, MDMA also
decreased the extracellular concentrations of DOPAC, HVA,
and 5-HIAA in the NAc at both ambient temperatures. This
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1319
MDMA 2.5 mg/kg
MDMA 5 mg/kg
b 500
400
DA (% of baseline)
DA (% of baseline)
a 500
300
200
100
400
300
200
100
0
0
1
2
Time (h)
3
4
5
c 200
d 200
DOPAC (%of baseline)
0
DOPAC (%of baseline)
-1
150
100
50
0
-1
0
1
2
3
Time (h)
4
5
-1
0
1
2
Time (h)
3
4
5
-1
0
1
2
Time (h)
3
4
5
150
100
50
0
1
2
Time (h)
3
4
5
e 200
f 200
HVA (% of baseline)
0
HVA (% of baseline)
-1
150
100
50
150
100
50
0
0
-1
0
1
2
Time (h)
3
4
5
Saline 20ºC
MDMA 20ºC
Saline 30ºC
MDMA 30ºC
Figure 5 Changes in the extracellular levels of dopamine (DA; a, b), DOPAC (c, d) and HVA (e, f) in the striatum of rats following administration of
MDMA (2.5 or 5 mg/kg, i.p.) at different ambient temperatures. Rats were maintained at a room temperature of 20 or 301C for 2.5 h before MDMA
injection and for 5 h after. At both room temperatures (20 and 301C), MDMA produced an increase in the content of DA compared with saline-treated
animals (main effect of treatment: for 2.5 mg/kg: F(1, 11) ¼ 14.61, Po0.001; F(1, 11) ¼ 3.51, Po0.05, respectively; for 5 mg/kg: F(1, 11) ¼ 22.53, Po0.001;
F(1, 8) ¼ 12.74, Po0.001, respectively) and a decrease in the levels of HVA (main effect of treatment: for 2.5 mg/kg: F(1, 14) ¼ 6.79, Po0.01;
F(1, 14) ¼ 17.85, Po0.001, respectively; for 5 mg/kg: F(1, 11) ¼ 26.61, Po0.001; F(1, 9) ¼ 23.12, Po0.001, respectively) and DOPAC (main effect of
treatment: for 2.5 mg/kg: F(1, 14) ¼ 19.26, Po0.001; F(1, 15) ¼ 12.01, Po0.001, respectively; for 5 mg/kg: F(1, 11) ¼ 81.67, Po0.001; F(1, 10) ¼ 45.63,
Po0.001 respectively). Values are expressed as a percentage of the mean of three measurements before drug administration. Each value is the mean7SEM
of 4–9 animals. Basal concentrations in saline-treated rats are shown in Table 1.
result could reflect a decrease in the metabolism of the
monoamines as a consequence of the ability of MDMA to
inhibit MAO activity. The MDMA-induced reduction in 5HIAA levels at the dose of 5 mg/kg was less pronounced
when MDMA was given to rats kept at 301C. A reduction in
extracellular 5-HT metabolism due to an increased MAO
inhibition could be responsible for this effect, but it seems
more likely that the high levels of 5-HIAA are reflecting a
higher 5-HT release into the extracellular space.
One further possibility that could explain the changes
induced by MDMA at high ambient temperature on
monoamine release and metabolism in the NAc is enhanced
penetration of MDMA through the blood–brain barrier.
However, alterations in the pharmacokinetic properties of
Neuropsychopharmacology
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1320
b 500
MDMA 2.5 mg/kg
5-HT (% of baseline)
5-HT (% of baseline)
a 500
400
300
200
100
0
MDMA 5 mg/kg
400
300
200
100
0
1
2
Time (h)
3
4
5
c 150
d 150
5-HIAA (% of baseline)
0
5-HIAA (% of baseline)
-1
100
50
-1
0
1
2
Time (h)
3
4
5
-1
0
1
2
Time (h)
3
4
5
100
50
0
0
-1
0
1
2
Time (h)
3
4
5
Saline 20°C
MDMA 20°C
Saline 30°C
MDMA 30°C
Figure 6 Changes in the extracellular levels of 5-HT (a, b) and 5-HIAA (c, d) in the striatum of rats following administration of MDMA (2.5 or 5 mg/kg,
i.p.) at different ambient temperatures. Rats were maintained at a room temperature of 20 or 301C for 2.5 h before MDMA injection and for 5 h after. At
both room temperatures (20 and 301C), MDMA produced an increase in the content of 5-HT compared with saline-treated animals (main effect of
treatment: for 2.5 mg/kg: F(1,11) ¼ 4.19, Po0.05; F(1, 14) ¼ 9.35, Po0.01, respectively; for 5 mg/kg: F(1, 11) ¼ 10.95 , Po0.001; F(1, 9) ¼ 10.46, Po0.001,
respectively) and a decrease in the levels of 5-HIAA (main effect of treatment: for 2.5 mg/kg: F(1, 14) ¼ 7.50, Po0.01; F(1, 14) ¼ 7.77, Po0.01, respectively;
for 5 mg/kg: F(1, 12) ¼ 18.97, Po0.001; F(1, 8) ¼ 3.37, Po0.05, respectively). The effects of MDMA on 5-HT and 5-HIAA levels were similar at both
ambient temperatures. Values are expressed as a percentage of the mean of three measurements before drug administration. Each value is the mean7SEM
of 4–9 animals. Basal concentrations in saline-treated rats are shown in Table 1.
the drug at elevated temperature can be discarded since
MDMA concentrations in the brain of rats at 301C were
similar to those obtained at 201C room temperature.
Administration of MDMA (2.5 or 5 mg/kg) had little effect
on rectal temperature, other than a transient hypothermia,
when the drug was given to rats housed at 201C, but it
produced a sustained and marked hyperthermia when
administered to rats housed at 301C, confirming previous
observations (Green et al, 2004). We have previously shown
that the initial hyperthermia that follows MDMA injection
appears to be due to dopamine release acting on D1
receptors and inhibition of normal heat loss mechanisms
that are normally occurring, such as tail vasodilation
(Mechan et al, 2002). Since heat loss through this
mechanism is presumably more difficult to achieve when
the animal is in a high ambient temperature, a clear
hyperthermia will occur and is unlikely to be due to greater
dopamine efflux and function, rather being due to the
environmental conditions. However, we and others, have
also found that increased 5-HT function is necessary to
enhance heat loss mechanisms when animals are in high
Neuropsychopharmacology
ambient temperature conditions. Decreasing cerebral 5-HT
content by administration of the tryptophan hydroxylase
inhibitor p-chlorophenylalanine or a neurotoxic dose of
MDMA or administration of the 5-HT antagonist methysergide results in heat-exposed rats having impaired
thermoregulation (Giacchino et al, 1983; Green et al, 2004;
Saadat et al, 2005). The fact that there is a greater 5-HT
efflux in the NAc at high ambient temperature is therefore
of interest, not necessarily because this region is responsible
for the heat loss mechanism per se, but rather as a reflection
that such a change does occur in specific brain regions and
could be involved in initiating heat loss mechanisms.
It seems clear that the enhanced locomotor activity
following MDMA is not the cause of the hyperthermic
response since MDMA produced a significant increase in
locomotor activity in rats housed at 201C but rectal
temperature did not increase. Furthermore, the absolute
locomotor response was no greater following MDMA in rats
housed at 301C than those housed at 201C. However, the
former group also experienced a marked hyperthermic
response. All these data argue against a relationship
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1321
between locomotor activity and MDMA-induced hyperthermia, a conclusion also made by Dafters (1995) following
his studies on hyperkinesis and hyperthermia following
MDMA administration.
Locomotor activity following administration of amphetamines is generally considered to result from increased
dopaminergic activity in the mesolimbic region, while
stereotypy is associated with dopamine release in the
striatum (Kelly et al, 1975; Fibiger and Phillips, 1974), and
therefore the greater increase in extracellular dopamine in
the NAc may account for the greater increase in locomotor
activity, above control values, in animals housed at high
ambient room temperature.
What is particularly interesting with regard to the
enhanced dopamine release in the NAc in rats housed at
high room temperature is its possible relationship to the
rewarding action of MDMA. The mesolimbic dopamine
system has long been suggested to be involved in the
rewarding properties of recreational drugs (Fibiger and
Phillips, 1974; Wise and Bozarth, 1982), including MDMA
(Beardsley et al, 1986). Low-dose MDMA has been shown to
have rewarding properties when given at standard room
temperature as it induces a positive effect in the CPP test
(Marona-Lewicka et al, 1996). Recently, Cornish et al (2003)
reported greater MDMA-induced social interaction behavior in rats housed at 301C compared with 201C and also
greater self-administration of MDMA at high temperature.
It is tempting to suggest that the enhanced mesolimbic
dopamine release seen at high temperature is responsible
for the behavioral changes seen by Cornish et al (2003).
In addition, evidence suggests that the 5-HT system may
also be involved in mediating the rewarding and stimulant
properties of MDMA either by direct or indirect mechanisms. Dopamine release in the ventral tegmental area may
be facilitated by 5-HT, possibly acting indirectly through a
GABAergic mechanism (Kalivas, 1993; Prisco et al, 1994;
Trifunovic and Brodie, 1996). Furthermore, various 5-HT
receptor subtypes have been shown to modulate dopamine
release in the NAc and the striatum (Benloucif and
Galloway, 1991; Chen et al, 1991; Benloucif et al, 1993;
Parsons and Justice, 1993; Lucas et al, 1997). Moreover, it
appears that 5-HT release and subsequent 5-HT1B receptor
(and possibly 5-HT2A receptor) stimulation is required for
MDMA-induced hyperlocomotion to develop (Callaway
et al, 1990; Kehne et al, 1996; McCreary et al, 1999). In
particular, since dopamine release in the NAc is positively
controlled by 5-HT1B (Boulenguez et al, 1996) and 5-HT2A
receptors (De Deurwaerdere and Spampinato, 1999), it may
be that the increase in locomotor activity induced by
MDMA is a consequence of an increase in dopaminergic
transmission mediated by 5-HT in the NAc (McCreary et al,
1999).
Therefore, the facilitatory effect of MDMA on dopamine
and 5-HT efflux in the NAc suggests that the rewarding
properties of MDMA could be more pronounced at high
ambient temperature.
Human recreational users of MDMA may experience
greater psychoactive effects of MDMA when taking it in
warm crowded conditions. The corollary of this, however, is
that high ambient temperature produces a greater hyperthermic response to the same MDMA dose, which is
associated with greater long-term neurotoxicity in rat
models (Broening et al, 1995; Malberg and Seiden, 1998;
O’Shea et al, 1998; Sanchez et al, 2004). This may suggest
that human recreational users put themselves at greater risk
by ingesting the drug in hot room conditions.
ACKNOWLEDGEMENTS
MIC thanks Ministerio de Ciencia y Tecnologia (Grant
SAF2001-1437), Ministerio de Sanidad (Grant FIS02/1885,
Grant G03/005), Plan Nacional sobre Drogas (Ministerio del
Interior), and Fundacion Mapfre Medicina for financial
support. VS thanks FIS for a studentship.
REFERENCES
Baldwin HA, Williams JL, Snares M, Ferreira T, Cross AJ, Green
AR (1994). Attenuation by chlormethiazole administration of the
rise in extracellular amino acids following focal ischaemia in the
cerebral cortex of the rat. Br J Pharmacol 112: 188–194.
Beardsley PM, Balster RL, Harris LS (1986). Self-administration of
methylenedioxymethamphetamine (MDMA) by rhesus monkeys. Drug Alcohol Depend 18: 149–157.
Benloucif S, Galloway MP (1991). Facilitation of dopamine release
in vivo by serotonin agonists: studies with microdialysis. Eur J
Pharmacol 200: 1–8.
Benloucif S, Keegan MJ, Galloway MP (1993). Serotonin-facilitated
dopamine release in vivo: pharmacological characterization.
J Pharmacol Exp Ther 265: 373–377.
Bilsky EJ, Hubbell CL, Delconte JD, Reid LD (1991). MDMA
produces a conditioned place preference and elicits ejaculation
in male rats: a modulatory role for the endogenous opioids.
Pharmacol Biochem Behav 40: 443–447.
Bilsky EJ, Reid LD (1991). MDL72222, a serotonin 5-HT3 receptor
antagonist, blocks MDMA’s ability to establish a conditioned
place preference. Pharmacol Biochem Behav 39: 509–512.
Boulenguez P, Rawlins JN, Chauveau J, Joseph MH, Mitchell SN,
Gray JA (1996). Modulation of dopamine release in the nucleus
accumbens by 5-HT1B agonists: involvement of the hippocampo-accumbens pathway. Neuropharmacology 35: 1521–1529.
Broening HW, Bowyer JF, Slikker Jr W (1995). Age-dependent
sensitivity of rats to the long term effects of the serotonergic neurotoxicant (7)-3,4-methylenedioxymethampheramine
(MDMA) correlates with the magnitude of the MDMA-induced
thermal response. J Pharmacol Exp Ther 275: 325–333.
Brown C, Osterloh J (1987). Multiple severe complications from
recreational ingestion of MDMA (‘Ecstasy’). J Am Med Assoc 258:
780–781.
Callaway CW, Wing LL, Geyer MA (1990). Serotonin release
contributes to the locomotor stimulant effects of 3,4-methylenedioxymethamphetamine in rats. J Pharmacol Exp Ther 254:
456–464.
Chen JP, van Praag HM, Gardner EL (1991). Activation of 5-HT3
receptor by 1-phenylbiguanide increases dopamine release in the
rat nucleus accumbens. Brain Res 543: 354–357.
Colado MI, O’Shea E, Granados R, Esteban B, Martı́n AB, Green AR
(1999). Studies on the role of dopamine in the degeneration
of 5-HT nerve endings in the brain of Dark Agouti rats following
3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy’)
administration. Br J Pharmacol 126: 911–924.
Cornish JL, Shahnawaz Z, Thompson MR, Wong S, Morley KC,
Hunt GE et al (2003). Heat increases 3,4-methylenedioxymethamphetamine self-administration and social effects in rats.
Eur J Pharmacol 482: 339–341.
Crespi D, Mennini T, Gobbi M (1997). Carrier-dependent
and Ca(2+)-dependent 5-HT and dopamine release induced
by (+)-amphetamine, 3,4-methylendioxymethamphetamine,
Neuropsychopharmacology
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1322
p-chloroamphetamine and (+)-fenfluramine. Br J Pharmacol
121: 1735–1743.
Dafters RI (1995). Effect of ambient temperature on hyperthermia
and hyperkinesis induced by 3,4-methylenedioxymethamphetamine (MDMA or ‘ecstasy’) in rats. Psychopharmacology 114:
505–518.
Daniela E, Brennan K, Gittings D, Hely L, Schenk S (2004). Effect of
SCH 23390 on (7)-3,4-methylenedioxymethamphetamine hyperactivity and self-administration in rats. Pharmacol Biochem
Behav 77: 745–750.
De Deurwaerdere P, Spampinato U (1999). Role of serotonin(2A)
and serotonin(2B/2C) receptor subtypes in the control of
accumbal and striatal dopamine release elicited in vivo by
dorsal raphe nucleus electrical stimulation. J Neurochem 73:
1033–1042.
Deutch AY, Cameron DS (1992). Pharmacological characterization
of dopamine systems in the nucleus accumbens core and shell.
Neuroscience 46: 49–56.
Dewar KM, Reader TA, Grondin L, Descarries L (1991).
[3H]paroxetine binding and serotonin content of rat and
rabbit cortical areas, hippocampus, neostriatum, ventral mesencephalic tegmentum, and midbrain raphe nuclei region.
Synapse 9: 14–26.
Esteban B, O’Shea E, Camarero J, Sanchez V, Green AR, Colado MI
(2001). 3,4-Methylenedioxymethamphetamine induces monoamine release, but not toxicity, when administered centrally at a
concentration occurring following a peripherally injected
neurotoxic dose. Psychopharmacology 154: 251–260.
Fibiger HC, Phillips AG (1974). Role of dopamine and norepinephrine in the chemistry of reward. J Psychiatr Res 11: 135–143.
Giacchino JL, Schertel ER, Horowitz JM, Horwitz BA (1983). Effect
of p-chlorophenylalanine on thermoregulation in unrestrained
rats. Am J Physiol 244: R299–R302.
Gold LH, Geyer MA, Koob GF (1989a). Neurochemical mechanisms involved in behavioral effects of amphetamines and related
designer drugs. NIDA Res Monogr 94: 101–126.
Gold LH, Hubner CB, Koob GF (1989b). A role for the mesolimbic
dopamine system in the psychostimulant actions of MDMA.
Psychopharmacology 99: 40–47.
Gold LH, Koob GF (1988). Methysergide potentiates the hyperactivity produced by MDMA in rats. Pharmacol Biochem Behav
29: 645–648.
Green AR, Sanchez V, O’Shea E, Saadat KS, Elliott JM, Colado MI
(2004). Effect of ambient temperature and a prior neurotoxic
dose of 3,4-methylenedioxymethamphetamine (MDMA) on
the hyperthermic response of rats to a single or repeated
(‘binge’ ingestion) low dose of MDMA. Psychopharmacology 173:
264–269.
Henry JA (1992). Ecstasy and the dance of death. BMJ 305: 5–6.
Henry JA, Jeffreys KJ, Dawling S (1992). Toxicity and deaths from
3,4-methylenedioxymethamphetamine (‘ecstasy’). Lancet 340:
384–387.
Hubner CB, Bird M, Rassnick S, Kornetsky C (1988). The threshold
lowering effects of MDMA (ecstasy) on brain-stimulation
reward. Psychopharmacology 95: 49–51.
Kalivas PW (1993). Neurotransmitter regulation of dopamine
neurons in the ventral tegmental area. Brain Res Brain Res Rev
18: 75–113.
Kankaanpaa A, Meririnne E, Lillsunde P, Seppala T (1998). The
acute effects of amphetamine derivatives on extracellular
serotonin and dopamine levels in rat nucleus accumbens.
Pharmacol Biochem Behav 59: 1003–1009.
Kehne JH, Ketteler HJ, McCloskey TC, Sullivan CK, Dudley MW,
Schmidt CJ (1996). Effects of the selective 5-HT2A receptor
antagonist MDL 100,907 on MDMA-induced locomotor stimulation in rats. Neuropsychopharmacology 15: 116–124.
Kelly PH, Seviour PW, Iversen SD (1975). Amphetamine and
apomorphine responses in the rat following 6-OHDA lesions of
Neuropsychopharmacology
the nucleus accumbens septi and corpus striatum. Brain Res 94:
507–522.
König JFR, Klippel RA (1963). The Rat Brain. A Stereotaxic Atlas of
the Forebrain and Lower Parts of the Brain Stem. Robert E
Krieger Publishing Co Inc.: New York.
Lamb RJ, Griffiths RR (1987). Self-injection of d,1-3,4-methylenedioxymethamphetamine (MDMA) in the baboon. Psychopharmacology 91: 268–272.
Lucas JJ, Segu L, Hen R (1997). 5-Hydroxytryptamine1B receptors
modulate the effect of cocaine on c-fos expression: converging
evidence using 5-hydroxytryptamine1B knockout mice and the
5-hydroxytryptamine1B/1D antagonist GR127935. Mol Pharmacol 51: 755–763.
Malberg JE, Seiden LS (1998). Small changes in ambient
temperature cause large changes in 3,4-methylenedioxymethamphetamine (MDMA)-induced serotonin neurotoxicity and core
body temperature in the rat. J Neurosci 18: 5086–5094.
Marona-Lewicka D, Rhee GS, Sprague JE, Nichols DE (1996).
Reinforcing effects of certain serotonin-releasing amphetamine
derivatives. Pharmacol Biochem Behav 53: 99–105.
McCreary AC, Bankson MG, Cunningham KA (1999). Pharmacological studies of the acute and chronic effects of (+)-3, 4methylenedioxymethamphetamine on locomotor activity: role
of 5-hydroxytryptamine(1A) and 5-hydroxytryptamine(1B/1D)
receptors. J Pharmacol Exp Ther 290: 965–973.
Mechan AO, Esteban B, O’Shea E, Elliott JM, Colado MI, Green AR
(2002). The pharmacology of the acute hyperthermic response
that follows administration of 3,4-methylenedioxymethamphetamine (MDMA, ‘ecstasy’) to rats. Br J Pharmacol 135: 170–180.
Mennicken F, Savasta M, Peretti-Renucci R, Feuerstein C (1992).
Autoradiographic localization of dopamine uptake sites in the
rat brain with 3H-GBR 12935. J Neural Transm Gen Sect 87: 1–14.
O’Shea E, Granados R, Esteban B, Colado MI, Green AR (1998).
The relationship between the degree of neurodegeneration of rat
brain 5-HT nerve terminals and the dose and frequency of
administration of MDMA (‘ecstasy’). Neuropharmacology 37:
919–926.
Parsons LH, Justice Jr JB (1993). Perfusate serotonin increases
extracellular dopamine in the nucleus accumbens as measured
by in vivo microdialysis. Brain Res 606: 195–199.
Prisco S, Pagannone S, Esposito E. (1994). Serotonin-dopamine
interaction in the rat ventral tegmental area: an electrophysiological study in vivo. J Pharmacol Exp Ther 271: 83–90.
Rudnick G, Wall SC (1992). The molecular mechanism of ‘ecstasy’
[3,4-methylenedioxymethamphetamine (MDMA)]: serotonin
transporters are targets for MDMA-induced serotonin release.
Proc Natl Acad Sci 89: 1817–1821.
Saadat KS, O’Shea E, Colado MI, Elliott JM, Green AR (2005). The
role of 5-HT in the impairment of thermoregulation observed in
rats administered MDMA (‘ecstasy’) when housed at high
temperature. Psychopharmacology (in press).
Sanchez V, Camarero J, Esteban B, Peter MJ, Green AR, Colado MI
(2001). The mechanisms involved in the long-lasting neuroprotective effect of fluoxetine against MDMA (‘ecstasy’)-induced
degeneration of 5-HT nerve endings in rat brain. Br J Pharmacol
134: 46–57.
Sanchez V, O’Shea E, Saadat KS, Elliott JM, Colado MI, Green AR
(2004). Effect of repeated (‘binge’) dosing of MDMA to rats
housed at normal and high temperature on neurotoxic damage
to cerebral 5-HT and dopamine neurones. J Psychopharmacol 18:
412–416.
Schechter MD (1991). Effect of MDMA neurotoxicity upon its
conditioned place preference and discrimination. Pharmacol
Biochem Behav 38: 539–544.
Schenk S, Gittings D, Johnstone M, Daniela E (2003). Development,
maintenance and temporal pattern of self-administration
maintained by ecstasy (MDMA) in rats. Psychopharmacology
169: 21–27.
Ambient temperature and monoamine release following MDMA
E O’Shea et al
1323
Screaton GR, Singer M, Cairns HS, Thrasher A, Sarner M, Cohen
SL (1992). Hyperpyrexia and rhabdomyolysis after MDMA
(‘ecstasy’) abuse. Lancet 339: 677–678.
Swerdlow NR, Koob GF (1985). Separate neural substrates of the
locomotor activating-properties of amphetamine, heroin, caffeine and corticotrophin releasing factor (CRF) in the rat.
Pharmacol Biochem Behav 23: 303–307.
Trifunovic RD, Brodie MS (1996). The effects of clomipramine on
the excitatory action of ethanol on dopaminergic neurons of the
ventral tegmental area in vitro. J Pharmacol Exp Ther 276: 34–40.
Vaccarino FJ, Amalric M, Swerdlow NR, Koob GF (1986). Blockade
of amphetamine but not opiate-induced locomotion following
antagonism of dopamine function in the rat. Pharmacol Biochem
Behav 24: 61–65.
White SR, Duffy P, Kalivas PW (1994). Methylenedioxymethamphetamine depresses glutamate-evoked neuronal firing and
increases extracellular levels of dopamine and serotonin in the
nucleus accumbens in vivo. Neuroscience 62: 41–50.
Wise RA, Bozarth MA (1982). Action of drugs of abuse on brain
reward systems: an update with specific attention to opiates.
Pharmacol Biochem Behav 17: 239–243.
Yamamoto BK, Spanos LJ (1988). The acute effects of methylenedioxymethamphetamine on dopamine release in the awakebehaving rat. Eur J Pharmacol 148: 195–203.
Neuropsychopharmacology