Exposure to prolonged controllable or uncontrollable stress affects GABAergic function in sub-regions of the hippocampus and the amygdala

The degree of behavioral control that an individual has over a stressor can critically determine its behavioral and neurochemical outcomes. Exposure to uncontrollable stress was previously shown to have detrimental effects on behavior, whereas exposure to equivalent controllable stress prevented these negative outcomes and even improved later stress coping. As many lines of evidence show, stress exposure can have maladaptive changes on inhibitory circuitry, and these effects were largely shown in the hippocampus and amygdala. In the current study we set out to examine alterations in GABAergic activity following exposure to the prolonged two way shuttle (TWS) avoidance task, focusing on the GABA-related factors glutamate decarboxylase (GAD)65, cholecystokinin (CCK) and neuropeptide Y (NPY). As recent views of the hippocampus assume regional specificity in hippocampal function, we examined different regions in the hippocampus, as well as the basolateral amygdala (BLA). Our findings reveal similar alterations in GAD65 in BLA for both controllable and uncontrollable stress exposure, but differential alterations in GAD65 and NPY in the dorsal dentate gyrus (DG). Synaptic plasticity and inhibitory activity in the dorsal DG was further assessed by applying different stimulation protocols and measuring evoked field potentials in vivo. Our results support a role for the DG in stress processing, emphasizing its sensitivity to the nature of the stressor. (C) 2016 Published by Elsevier Inc.