Papers by Angela Sarabdjitsingh
Endocrinology, Jul 1, 2013
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PLOS ONE, 2016
In recent years it has become clear that corticosteroid hormones (such as corticosterone) are rel... more In recent years it has become clear that corticosteroid hormones (such as corticosterone) are released in ultradian pulses as a natural consequence of pituitary-adrenal interactions. All organs, including the brain, are thus exposed to pulsatile changes in corticosteroid hormone level, important to ensure full genomic responsiveness to stress-induced surges. However, corticosterone also changes neuronal excitability through rapid non-genomic pathways, particularly in the hippocampus. Potentially, background excitability of hippocampal neurons could thus be changed by pulsatile exposure to corticosteroids. It is currently unknown, though, how neuronal activity alters during a sequence of corticosterone pulses. To test this, hippocampal cells were exposed in vitro to four consecutive corticosterone pulses with a 60 min inter-pulse interval. During the pulses we examined four features of hippocampal signal transfer by the main excitatory transmitter glutamate-i.e., postsynaptic responses to spontaneous release of presynaptic vesicles, postsynaptic GluA2-AMPA receptor dynamics, basal (evoked) field responses, and synaptic plasticity, using a set of high resolution imaging and electrophysiological approaches. We show that the first pulse of corticosterone causes a transient increase in miniature EPSC frequency, AMPA receptor trafficking and synaptic plasticity, while basal evoked field responses are unaffected. This pattern is not maintained during subsequent applications: responses become more variable, attenuate or even reverse over time, albeit with different kinetics for the various experimental endpoints. This may indicate that the beneficial effect of ultradian pulses on transcriptional regulation in the hippocampus is not consistently accompanied by short-term perturbations in background excitability. In general, this could be interpreted as a means to keep hippocampal neurons responsive to incoming signals related to environmental challenges.
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Endocrinology, Jul 1, 2013
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Proceedings of the National Academy of Sciences of the United States of America, Jan 30, 2014
The rodent adrenal hormone corticosterone (CORT) reaches the brain in hourly ultradian pulses, wi... more The rodent adrenal hormone corticosterone (CORT) reaches the brain in hourly ultradian pulses, with a steep rise in amplitude before awakening. The impact of a single CORT pulse on glutamatergic transmission is well documented, but it remains poorly understood how consecutive pulses impact on glutamate receptor trafficking and synaptic plasticity. By using high-resolution imaging and electrophysiological approaches, we report that a single pulse of CORT to hippocampal networks causes synaptic enrichment of glutamate receptors and increased responses to spontaneously released glutamatergic vesicles, collectively abrogating the ability to subsequently induce synaptic long-term potentiation. Strikingly, a second pulse of CORT one hour after the first--mimicking ultradian pulses--completely normalizes all aspects of glutamate transmission investigated, restoring the plastic range of the synapse. The effect of the second pulse is precisely timed and depends on a nongenomic glucocorticoid...
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PLoS ONE, 2012
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Pharmacological Reviews, 2012
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Neuropharmacology, 2014
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Journal of Neuroendocrinology, 2010
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Journal of Neurochemistry, 2006
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Journal of Neurochemistry, 2008
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The Journal of Comparative Neurology, 2008
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European Neuropsychopharmacology, 2012
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European Journal of Neuroscience, 2007
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Endocrinology, 2008
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Endocrinology, 2010
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Endocrinology, 2010
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Brain Research, 2010
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Brain Research, 2009
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Papers by Angela Sarabdjitsingh