Epinephrine fails to enhance performance of food-deprived rats on a delayed spontaneous alternation task.

Increases in blood glucose levels after epinephrine injection appear to contribute to the hormone's effects on learning and memory. The present experiment evaluated whether epinephrine-induced enhancement of spontaneous alternation performance would be attenuated in fasted rats that had blunted increases in circulating glucose levels after injections of epinephrine. Rats deprived of food for 24 h prior to injection of epinephrine exhibited significant attenuation of the increase in blood glucose levels seen in fed rats. When the rats were tested on a delayed spontaneous alternation task, epinephrine enhanced performance in fed rats but not in rats deprived of food for 24 h. These findings are consistent with the view that hyperglycemia subsequent to epinephrine injections contributes to the memory-enhancing effects of epinephrine.