Caffeine and cocaine interaction on memory consolidation in mice.

The main aim of this study was to investigate the interaction between the effects of caffeine and cocaine on memory consolidation in mice. For this purpose, CD1 mice were used; they were injected intraperitoneally and tested in a one-trial inhibitory avoidance task. The apparatus consisted of two compartments, one lighted and the other in darkness. On the training day, the animal had to go from the lighted to the dark compartment, where it received an electric shock. On the test day, carried out in our experiments 24 hours later, the time the animal waited to enter the dark compartment is the measure of its retention (for further details, see Methods). Three sets of experiments were carried out. In a first set, immediately posttraining, caffeine (0.25, 0.5 and 1 mg/kg) or cocaine (1, 2.5 and 5 mg/kg) administrations enhanced the memory consolidation of mice. In a second set, the D2 dopamine receptor antagonist, (-)-sulpiride, antagonized the enhancing effect of caffeine on memory. In a third set, a clear interaction between caffeine and cocaine was evident. The results are interpreted in terms of interaction of the drugs used with the dopaminergic system.