Improvement of memory for an operant response by post-training glucose in mice

Previous experiments have shown that a post-training glucose injection can retroactively and non-contingently improve the retention of a previously learned association. To date, the memory-improving action of glucose has only been demonstrated in rats for negatively-motivated tasks. The present experiment sought to generalize these previous results by examining the effects in mice of post-training glucose injections on the retention of an operant bar-pressing response. The results show that post-training glucose can retroactively and non-contingently improve the retention of an appetitively motivated task in mice. There was a U-shaped relationship between the dose of glucose and the effect on memory similar to the ones already observed in rats using negatively motivated training. The implications of these results for an endogenous memory modulation mechanism are discussed.