Object recognition in mice: improvement of memory by glucose.

In most of the demonstrations of the memory-improving action of glucose in animals, training conditions have included electric shocks, food deprivation, or food rewards, all of which produce changes in blood glucose. In these experiments, training conditions may interact with the exogenous injection of glucose and make it more difficult to interpret results. To circumvent this problem, the ability of glucose to improve memory in an object-recognition task was examined. Animals were first habituated to an open field. The next day, they were placed in the same open field together with two identical objects and the time spent observing and exploring the objects was recorded. The animals were then given either a saline or an immediate or delayed (1 and 5 h) glucose (500 mg/kg) injection or no treatment. On the final day, animals were placed in the open field with a previously observed object and a new object. Exploration time was recorded. Results showed that the animals that received the immediate glucose injection spent significantly more time exploring the new object, suggesting that glucose retroactively and noncontingently improved the memory for the previously observed object.