Repeated restraint stress alters glutamatergic but not gabaergic transmission within the paraventricular nucleus of the hypothalamus

The hypothalamic paraventricular nucleus (PVN) plays a key role in the activation of the hypothalamic-pituitary-adrenal axis (HPA) in response to stressors. Wistar rats were subjected to restraint lasting 10 min and repeated twice daily for 3 days. Brain slices were prepared 24 h after the last restraint session and studied ex vivo. Whole-cell patch-clamp method was used to record spontaneous excitatory and inhibitory postsynaptic currents (sEPSCs and sIPSCs) from presumed parvocellular neurosecretory neurons in slices containing a part of the PVN. Repeated restraint stress resulted in an increase in the mean frequency of sEPSCs and in a decrease in the rise time and the decay time constant of sEPSCs. There were no changes in the mean amplitude of sEPSC. All measured parameters of sIPSCs remained unaltered. The relationship between the injected current and the spiking rate of parvocellular neurons was reduced. These data indicate that restraint stress, repeated for 3 days, selectively enhances the excitatory inputs to parvocellular neurons of the PVN, most likely via a combination of pre- and postsynaptic mechanisms. These changes are accompanied by a decrease in the intrinsic excitability of PVN neurons. Support: “DeMeTer” and statutory funds from the Institute of Pharmacology.