The central amygdala is involved in the conditioned but not in the meal-induced cephalic insulin response in the rat

The central nucleus of the amygdala (CEA) is considered to be involved in the regulation of autonomic correlates of fear. Its involvement in the control of autonomic functions other than elicited by fear has received little attention. The effects of a bilateral electrolytical lesion of the CEA on feeding related insulin responses have been analyzed in male Wistar rats. The cephalic phase of the insulin response is a vagally mediated elevation of plasma insulin concentration during the first minute after meal onset, before any increase in plasma glucose can be noticed. This response can also be entrained to environmental stimuli. The insulin response elicited under these conditions is due to conditioning. CEA lesioning abolished the conditioned insulin response but not the early insulin elevation during the presentation of food. The CEA lesion failed to affect plasma glucose levels in both the meal-induced and conditioned test situations, To our knowledge this is the first study that shows that the CEA is also involved in the organization of conditioned metabolic endocrine responses.