Effects of acute and repeated restraint stress on GABA efflux in the rat basolateral and central amygdala.

Stress can precipitate onset of multiple mood-related disorders, including depression. Examination of the neural basis of this phenomenon has highlighted the amygdala as a key component. Alterations in amygdalar activity and structure accompany various mood-related disorders, and interestingly, amygdalar morphology and behavior can be altered in animals subjected to repeated stress. Gamma-aminobutyric acid (GABA) transmission in the amygdala represents an important means by which information flow, activity, and function can be controlled; therefore, we determined the effects of acute and repeated restraint stress (RRS) on GABA efflux in the basolateral and central amygdalar complexes. In vivo microdialysis revealed that acute restraint stress increased GABA efflux in the basolateral amygdala, whereas central amygdala efflux remained unchanged. Animals subjected to prior repeated stress displayed no acute stress-mediated increases in GABA efflux in the basolateral amygdala, an event accompanied by no changes in basal GABA concentrations. Conversely, repeated restraint stress had no effect on GABA efflux or basal GABA levels in the CeA. Collectively, these data demonstrate that acute stress elicits unique and region-specific increases in GABA efflux in the rat amygdala, and that prior repeated stress differentially modifies this response.