Visualization of stress-responsive inhibitory circuits in the GAD65-eGFP transgenic mice.

Here, we have revealed that a subset of GABAergic neurons in the mouse brain became activated during systemic stress response. Stress-induced expression of immediate early gene product c-Fos, as a marker of neuronal activation was visualized in a transgenic mouse line expressing enhanced green fluorescent protein (eGFP) under the control of the regulatory region of mouse glutamic acid decarboxylase (GAD) 65 gene. In most GABAergic regions egfp transgene expression corresponded to acknowledged distribution of GABA neurons. Ether inhalation, as a strong systemic stressor induced c-Fos expression throughout the stress-related circuit, and did not affect the distribution and expression of the eGFP-transgene. Stress provoked strong neuronal activation in the piriform cortex, midline thalamic nuclei, lateral septum (LS), bed nucleus of the stria terminalis (BNST), and in parvocellular part of the hypothalamic paraventricular nucleus (PVN) as revealed by c-Fos immunfluorescence. Cells in the LS, BNST, and AHA including the subparaventricular zone (SPVZ) displayed significant eGFP/c-Fos co-localization, revealing stress-responsive GABAergic neurons. None of the stress-activated neurons within the medial parvocellular subdivision of the PVN were GABAergic. Our present results suggest that stress-recruited GABAergic neuron populations are preferentially located in distinct limbic and hypothalamic regions and these neurons might be involved in an inhibitory mechanism that counteract the endocrine, autonomic and behavioral aspects of the stress response. Furthermore, the present GAD65-eGFP transgenic model seems to be a relevant tool to analyze inhibitory control of the central stress circuit at single cell level.