Article date: September 2017
By: Yonggang Gao, Jing‐Jing Zhou, Yun Zhu, Li Wang, Therese A Kosten, Xiangjian Zhang, De‐Pei Li in Volume 174, Issue 17, pages 2929-2940
Background and purpose
Chronic stress impairs GABAA (GABA type A) receptor‐mediated inhibition in the hypothalamic paraventricular nucleus (PVN). It is not clear whether GABAB receptor function is also altered. We hypothesize that chronic stress alters GABAB receptor function in PVN corticotrophin‐releasing hormone (CRH) neurons to control hypothalamus‐pituitary–adrenal axis activity.
Experimental Approach
Whole‐cell patch clamp recordings were made of PVN‐CRH neurons expressing eGFP driven by CRH promoter in brain slices from unstressed rats and rats exposed to chronic unpredictable mild stress (CUMS).
Key Results
CUMS elevated the basal circulating corticosterone levels and increased the basal firing activity of PVN‐CRH neurons. Microinjection of GABAB receptor agonist baclofen into the PVN suppressed the increased corticosterone levels in CUMS rats compared with unstressed rats. CUMS blunted the baclofen‐induced inhibition on PVN‐CRH neurons and outward currents in these neurons. Furthermore, CUMS reduced expression of GABAB1 (GABABR1) protein in the PVN. Blocking NMDA receptors with AP5 restored the reduced baclofen‐induced currents in CUMS rats but had no effect on GABAB1 expression. Furthermore, CUMS treatment augmented the baclofen‐induced decrease in the frequency of glutamatergic excitatory postsynaptic currents (EPSCs) and GABAergic inhibitor postsynaptic currents in PVN‐CRH neurons. The GABAB receptor antagonist CGP55845 increased the firing activity of PVN‐CRH neurons only in CUMS‐treated rats and not in unstressed rats.
Conclusions and Implications
These findings suggest that chronic stress impairs postsynaptic GABAB receptor function but augments presynaptic GABAB receptor function in controlling glutamatergic and GABAergic synaptic inputs in PVN‐CRH neurons.
DOI: 10.1111/bph.13924
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