Memory enhancement with posttraining intraventricular glucose injections in rats

Recent findings suggest that peripheral epinephrine enhancement of memory storage may be mediated in part by an increase in circulating glucose levels subsequent to epinephrine release or injection. Because glucose, unlike epinephrine, has ready access to the central nervous system, it is possible that glucose acts directly on central processes to enhance memory. To test this possibility, rats were trained on a one-trial inhibitory avoidance task and received immediate or delayed injections of glucose in artificial cerebrospinal fluid. On retention tests 24 hr after training, animals that received 3 or 5 micrograms glucose (in 1 microl cerebrospinal fluid over 3 min) had significantly enhanced performance of the learned response. These findings are consistent with the view that glucose can regulate the storage of new information by acting on central processes. Whether there are additional peripheral contributions to glucose effects on memory remains to be determined.