Epinephrine inhibits feeding nonspecifically in the rat

The hypothesis that epinephrine (EPI) and pancreatic glucagon (PG) inhibit feeding by activating a common physiological satiety mechanism was tested by comparing the two agents' behavioral effects. In several tests of specificity, EPI and PG had functionally different inhibitory actions. Intraperitoneal injection of 6.25-50 μg/kg EPI and 100-400 μg/kg PG elicited overlapping dose-related inhibitions of intake of milk diet in rats maintained ad lib on pelleted chow. Twenty-five to 50 μg/kg EPI also elicited anomalous behaviors that are not normally associated with feeding, including supine postures with limbs extended and crawling with trunk dorsoflexed and abdomen pressed against cage floor. EPI elicited similar anomalous behaviors in rats that either sham fed with open gastric cannulas, drank after water deprivation, or were presented neither food nor water. Fifty to 200 μg/kg EPI also inhibited water intake in the thirsty rats, and 25-50 μg/kg EPI inhibited sham feeding. PG, in contrast, neither elicited anomalous behaviors nor inhibited water intake nor inhibited sham feeding. These data demonstrate that the inhibitory actions of exogenous EPI and PG are functionally dissociable. We conclude that 25-200 μg/kg EPI acts nonspecifically to produce anorexia and adipsia, while PG elicits postprandial satiety.