Effects of adrenal demedullation on the conditioned emotional response and on the memory improving action of glucose.

Results of previous experiments have demonstrated that posttraining, noncontingent ingestion of sucrose solutions, or injection of glucose solutions improve retention of various learning tasks. In the present experiment, we tested the hypothesis that this effect is due to a glucose-stimulated release of epinephrine from the adrenal medulla by testing the effect of posttraining glucose injections on retention of a conditioned emotional response (CER) in demedullated rats. In a preliminary experiment, demedullated rats were found to be deficient at acquiring the CER, but a similar deficit in sham-operated animals suggested that this was due to the surgical procedure rather than to the absence of the adrenal medulla. When appropriate shock parameters were used, posttraining glucose improved retention of the CER in a manner parallel to the effect of this treatment in normal rats. It was concluded that the memory improving effect of posttraining glucose does not involve an effect of this substance on the adrenal medulla.