Stress-induced plasticity of excitatory and inhibitory postsynaptic currents in rat central neurons

Corticotropin-releasing hormone (CRH)-synthesizing neurons of the hypothalamic paraventricular nucleus (PVN) play a key role in the activation of the hypothalamic-pituitary-adrenal axis (HPA). We used whole-cell patchclamping to record spontaneous and miniature excitatory and inhibitory postsynaptic currents (sEPSCs/mEPSCs and sIPSCs/mIPSCs) from parvocellular neuroendocrine neurons of the rat PVN in ex vivo brain slices. Repeated restraint stress (10 min; twice daily for 3 days) resulted in an increase in the mean frequency of sEPSCs/mIPSCs and in a decrease in the rise time and the decay time constant of sEPSCs/mEPSCs. There was no change in the mean amplitude of sEPSCs/mIPSCs. The parameters characterizing sIPSCs/mIPSCs remained unaltered. We also studied the effects of repeated injections of corticosterone, as a model of a chronic stress, on sEPSCs and sIPSCs recorded from layer II/III pyramidal neurons in ex vivo slices of the rat frontal cortex. Corticosterone administered repeatedly for 7, 14 and 21 days induced an increase in the frequency but not the amplitude of sEPSCs. Collectively, these studies suggest that repeated stress appears to selectively affect glutamatergic, but not GABAergic transmission in the rat hypothalamus and frontal cortex, and suggest that repeated stress induces an enhancement of spontaneous glutamate release from presynaptic terminals. L10.2