Abstract
Consequences of synaptic plasticity in the lamprey spinal CPG are analyzed by means of simulations. This is motivated by the effects substance P (a tachykinin) and serotonin (5-hydroxytryptamin; 5-HT) have on synaptic transmission in the locomotor network. Activity-dependent synaptic depression and potentiation have recently been shown experimentally using paired intracellular recordings. Although normally activity-dependent plasticity presumably does not contribute to the patterning of network activity, this changes in the presence of the neuromodulators substance P and 5-HT, which evoke significant plasticity. Substance P can induce a faster and larger depression of inhibitory connections but potentiation of excitatory inputs, whereas 5-HT induces facilitation of both inhibitory and excitatory inputs. Changes in the amplitude of the first postsynaptic potential are also seen. These changes could thus be a potential mechanism underlying the modulatory role these substances have on the rhythmic network activity.
The aim of the present study has been to implement the activity dependent synaptic depression and facilitation induced by substance P and 5-HT into two alternative models of the lamprey spinal locomotor network, one relying on reciprocal inhibition for bursting and one in which each hemicord is capable of oscillations. The consequences of the plasticity of inhibitory and excitatory connections are then explored on the network level.
In the intact spinal cord, tachykinins and 5-HT, which can be endogenously released, increase and decrease the frequency of the alternating left-right burst pattern, respectively. The frequency decreasing effect of 5-HT has previously been explained based on its conductance decreasing effect on K Ca underlying the postspike afterhyperpolarization (AHP). The present simulations show that short-term synaptic plasticity may have strong effects on frequency regulation in the lamprey spinal CPG. In the network model relying on reciprocal inhibition, the observed effects substance P and 5-HT have on network behavior (i.e., a frequency increase and decrease respectively) can to a substantial part be explained by their effects on the total extent and time dynamics of synaptic depression and facilitation. The cellular effects of these substances will in the 5-HT case further contribute to its network effect.
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References
Abbott L, Sen K, Variela J, Nelson S (1997) Synaptic depression and cortical gain control. Science 275:220-224.
Abraham WC, Bear MF (1996) Metaplasticity: The plasticity of synaptic plasticity. Trends Neurosci. 19:126-130.
Bower JM, Beeman D (1998) The Book of GENESIS. Springer-Verlag, New York.
Brodin L, Tråvén HGC, Lansner A, Wallén P, Ekeberg Ö, Grillner S (1991) Computer simulations of N-methyl-D-aspartate receptor-induced membrane properties in a neuron model. J. Neurophysiol. 66:473-484.
Buchanan JT (1982) Identification of interneurons with contralateral, caudal axons in the lamprey spinal cord: Synaptic interactions and morphology. J. Neurophysiol. 47:961-975.
Buchanan JT (1992) Neural network simulations of coupled locomotor oscillators in the lamprey spinal cord. Biol. Cybern. 66: 367-374.
Buchanan JT (1996) Lamprey spinal interneurons and their roles in swimming activity. Brain Behav. Evol. 48:287-296.
Buchanan JT (1999) Commissural interneurons in rhythm generation and intersegmental coupling in the lamprey spinal cord. J. Neurophysiol. 81:2037-2045.
Buchanan JT, Grillner S (1987) Newly identified "glutamate interneurons" and their role in locomotion in the lamprey spinal cord. Science 236:312-314.
Cangiano L, Woolley JD, Wallen P, Grillner S (2000) The isolated lamprey hemicord is capable of generating coordinated rhythmic motor activity. Soc. Neurosci. Abstr. 26:1997.
Crick F, Koch C (1990) Towards a neurobiological theory of consciousness. Semin. Neurosci. 2:263-275.
Ekeberg Ö (1993) A combined neuronal and mechanical model of fish swimming. Biol. Cybern. 69:363-374.
Ekeberg Ö, Grillner S (1999) Simulations of neuromuscular control in lamprey swimming. Phil. Trans. R. Soc. Lond. B. 354:895-902.
Ekeberg Ö, Wallén P, Lansner A, Tråvén H, Brodin L, Grillner S (1991) A computer-based model for realistic simulations of neural networks. I: The single neuron and synaptic interaction. Biol. Cybern. 65:81-90.
El Manira A, Tegnér J, Grillner S (1994) Calcium-dependent potassium channels play a critical role for burst termination in the locomotor network in lamprey. J. Neurophysiol. 72:1852-1861.
Fagerstedt P, Deliagina TG, Wallén P, Orlovsky GN, Grillner S (1997) Supraspinal and spinal inputs to lateral and crossed interneurons in the lamprey spinal cord. Soc. Neurosci. Abstract. (pt. 1) 23:764.
Friesen WO (1994) Reciprocal inhibition: A mechanism underlying oscillatory animal movements. Neurosci. Biobehav. Rev. 18:547-553.
Gray CM (1994) Synchronous oscillations in neuronal systems: Mechanisms and functions. J. Comput. Neurosci. 1:11-38.
Grillner S, Deliagina T, Ekeberg Ö, El Manira A, Hill RH, Lansner A, Orlovsky GN, Wallén P (1995) Neural networks that co-ordinate locomotion and body orientation in lamprey. Trends Neurosci. 18: 270-279.
Grillner S, Ekeberg Ö, El Manira A, Lansner A, Parker D, Tegnér J, Wallén P (1998a) Intrinsic function of a neuronal network: A vertebrate central pattern generator. Brain Res. Rev. 26:184-197.
Grillner S, Parker D, El Manira A (1998b) Vertebrate locomotion: A lamprey perspective. Ann. N.Y. Acad. Sci. 860:1-18.
Grillner S, Wallén P, Brodin L, Lansner A (1991) Neuronal network generating locomotor behavior in lamprey: Circuitry, transmitters, membrane properties, and simulation. Ann. Rev. Neurosci. 14:169-199.
Hellgren J, Grillner S, Lansner A (1992) Computer simulation of the segmental neural network generating locomotion in lamprey by using populations of network interneurons. Biol. Cybern. 68: 1-13.
Hellgren Kotaleski J, Grillner S, Lansner A (1999a) Neural mechanisms potentially contributing to the intersegmental phase lag in lamprey. I. Segmental oscillations dependent on reciprocal inhibition. Biol. Cybern. 81:317-330.
Hellgren Kotaleski J, Lansner A, Grillner S (1999b) Neural mechanisms potentially contributing to the intersegmental phase lag in lamprey. II. Hemisegmental oscillations produced by mutually coupled excitatory neurons. Biol. Cybern. 81:299-315.
Hempel CH, Hartman KH, Wang XJ, Turrigano G, Nelson SB (2000) Multiple forms of short-term plasticity at excitatory synapses in rat medial prefrontal cortex. J. Neurophysiol. 83:3031-3041.
Hill R, Matsushima T, Schotland J, Grillner S (1992) Apamin blocks the slow AHP in lamprey and delays termination of locomotor bursts. NeuroReport 30:943-945.
Laurent G, Davidowitz H (1994) Encoding of olfactory information with oscillating neural assemblies. Science 265:1872-1875.
Marder E, Calabrese R (1996) Principles of rhythmic motor pattern generation. Physiol. Rev. 76:687-717.
Matsushima T, Grillner S (1992) Local serotonergic modulation of calcium-dependent potassium channels controls intersegmental coordination in the lamprey spinal cord. J. Neurophysiol. 67: 1683-1690.
McClellan AD, Hagevik A (1997) Descending control of turning locomotor activity in larval lamprey: Neurophysiology and computer modeling. J. Neurophysiol. 78:214-228.
Milner B, Squire LR, Kandel ER (1998) Cognitive neuroscience and the study of memory. Neuron. 20:445-468.
Nadim F, Manor Y (2000) The role of short-term synaptic dynamics in motor control. Curr Opin Neurobiol. 10(6):683-690.
Nelson SB, Variela JA, Sen K, Abbott LF (1997) Functional significance of synaptic depression between cortical neurons. In: Bower JM, ed. Computational Neuroscience: Trends in Research. Plenum Press, New York. pp. 429-434.
Parker D (2000) Activity and calcium-dependent mechanisms maintain reliable interneuron synaptic transmission in a rhythmic neural network. J. Neurosci. 20:1754-1766.
Parker D (unpublished) The activity-dependent plasticity of segmental and intersegmental synaptic connections in the lamprey spinal cord (motoneurons and interneurons) (private communication).
Parker D, Grillner S (1996) Tachykinin-mediated modulation of sensory neurons, interneurons, and synaptic transmission in the lamprey spinal cord. J. Neurophysiol. 76:4031-4039.
Parker D, Grillner S (1998) Cellular and synaptic modulation underlying substance P-mediated plasticity of the lamprey locomotor network. J. Neurosci. 18:8095-8110.
Parker D, Grillner S (1999) Activity-dependent metaplasticity of inhibitory and excitatory synaptic transmission in the lamprey spinal cord locomotor network. J. Neurosci. 19:1647-1656.
Parker D, Grillner S (2000) The activity-dependent plasticity of segmental and intersegmental synaptic connections in the lamprey spinal cord. Eur. J. Neurosci. 12:2135-2146.
Parker D, Zhang W, Grillner S (1998) Substance P modulates NMDA responses and causes long-term protein synthesis-dependent modulation of the lamprey locomotor network. J. Neurosci. 18:4800-4813.
Rovainen CM (1983) Identified neurons in the lamprey spinal cord and their roles in fictive swimming. In: Roberts A, Roberts BL, eds. Neural Origin of Rhythmic Movements. Cambridge University Press, Cambridge. pp. 305-330.
Singer W(1993) Synchronization of cortical activity and its putative role in information processing and learning. Ann. Rev. Physiol. 55: 349-374.
Skinner FK, Kopell N, Marder E (1994) Mechanisms for oscillation and frequency control in reciprocally inhibitory model neural networks. J. Comput. Neurosci. 1:69-87.
Tabak J, Senn W, O'Donovan MJ, Rinzel J (2000) Modeling of spontaneous activity in developing spinal cord using activity-dependent depression in an excitatory network. J. Neurosci. 20(8):3041-3056.
Tegnér J, Grillner S (1999) Interactive effects of the (GABAB)-ergic modulation of calcium channels and calcium-dependent potassium channels in lamprey. J. Neurophysiol. 81:1318-1329.
Tegnér J, Hellgren Kotaleski J, Lansner A, Grillner S (1997) Low voltage activated calcium channels in the lamprey locomotor network: Simulation and experiment. J. Neurophysiol. 77:1795-1812.
Tegnér J, Lansner A, Grillner S (1998) Modulation of burst frequency by calcium-dependent potassium channels in the lamprey locomotor system: Dependence of the activity level. J. Comput. Neurosci. 5:121-140.
Tråvén HGC, Brodin L, Lansner A, Ekeberg Ö, Wallén P, Grillner S (1993) Computer simulations of NMDA and non-NMDA receptor-mediated synaptic drive: Sensory and supraspinal modulation of neurons and small networks. J. Neurophysiol. 70:695-709.
Wadden T, Hellgren J, Lansner A, Grillner S (1997) Intersegmental coordination in the lamprey: Simulations using a network model without segmental boundaries. Biol. Cybern. 76:1-9.
Wallén P, Buchanan JT, Grillner S, Hill RH, Christenson J, Hökfelt T (1989) Effects of 5-hydroxytryptamine on the afterhyperpolarization, spike frequency regulation, and oscillatory membrane properties in lamprey spinal cord neurons. J. Neurophysiol. 61:759-768.
Wallén P, Ekeberg Ö, Lansner A, Brodin L, Tråvén H, Grillner S (1992) A computer-based model for realistic simulations of neural networks. II. The segmental network generating locomotor rhythmicity in the lamprey. J. Neurophysiol. 68:1939-1950.
Wikström M, El Manira A (1998) Calcium influx through N-and P/Q-type channels activate apamin-sensitive calcium-dependent potassium channels generating the late after hyperpolarization in lamprey spinal neurons. Eur. J. Neurosci 10:1528-1532.
Williams TL (1992) Phase coupling by synaptic spread in chains of coupled neuronal oscillators. Science 258:662-665.
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Kozlov, A., Kotaleski, J.H., Aurell, E. et al. Modeling of Substance P and 5-HT Induced Synaptic Plasticity in the Lamprey Spinal CPG: Consequences for Network Pattern Generation. J Comput Neurosci 11, 183–200 (2001). https://doi.org/10.1023/A:1012806018730
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DOI: https://doi.org/10.1023/A:1012806018730