AVERSIVE AND APPETITIVE EVENTS EVOKE THE RELEASE OF CORTICOTROPIN-RELEASING HORMONE AND BOMBESIN-LIKE PEPTIDES AT THE CENTRAL NUCLEUS OF THE AMYGDALA

There is wide agreement that corticotropin-releasing hormone (CRH) sys tems within the brain are activated by stressful stimuli. There is als o mounting evidence for the role of bombesin (BN)-like peptides in the mediation of the stress response. To date, however, the extent to whi ch other stimuli increase the activity of these peptidergic systems ha s received little attention. In the present investigation we validated and used in vivo microdialysis sampling followed by ex vivo radioimmu noassays to monitor the release of CRH and BN-like peptides during app etitive (food intake) and stressful (restraint) events. It is demonstr ated for the first time that the in vivo release of CRH and BN-like pe ptides at the central nucleus of the amygdala was markedly increased b y both stressor exposure and food ingestion. In fact, the meal-elicite d rise of CRH release was as great as that associated with 20 min of r estraint stress. Paralleling these findings, circulating ACTH and cort icosterone levels were also increased in response to both food intake and restraint. Contrary to the current views, these results indicate t hat either food ingestion is interpreted as a ''stressful'' event by c ertain neural circuits involving the central amygdala or that the CRH- and BN-related peptidergic systems may serve a much broader role than previously envisioned. Rather than evoking feelings of fear and anxie ty, these systems may serve to draw attention to events or cues of bio logical significance, such as those associated with food availability as well as those posing a threat to survival.