STIMULATION OF THE AMYGDALA BY GLUTAMATE FACILITATES CORTICOTROPIN-RELEASING FACTOR RELEASE FROM THE MEDIAN-EMINENCE AND ACTIVATION OF THE HYPOTHALAMIC-PITUITARY-ADRENAL AXIS IN STRESSED RATS

The role of the amygdala in the regulation of hypothalamic release of corticotropin-releasing factor (CRF) was investigated, Microinjection of glutamate (50 nmol) into the amygdala resulted in increased plasma corticosterone in male rats previously subjected to a 14-day unpredictable stressor paradigm (p less than or equal to 0.05 vs. saline-injected controls). A long-lived increase in corticosterone levels was also observed in rats which were urethane-anesthetized (1.35 g/kg) 3 h prior to glutamate microinjection (p less than or equal to 0.01 vs, saline-injected controls), These effects on plasma corticosterone were observed despite the presence of high basal levels of corticosterone. Furthermore, microperfusion of glutamate (3-300 mu M) into the amygdala of urethane-anesthetized rats resulted in a dose-dependent increase in CRF release from the median eminence, as assessed by in vivo microdialysis (p less than or equal to 0.025 vs. basal), These results indicate a facilitating role for the amygdala in stress-induced increases in CRF release and subsequent adrenocortical activation.