Post-training minaprine enhances memory storage in mice: involvement of D1 and D2 dopamine receptors

Post-training administration of minaprine (2.5, 5 and 10 mg/kg) dose-dependently improved retention of an inhibitory avoidance response in mice. Animals receiving nine daily injections of 5 mg/kg and administered a challenge dose post-training showed an improvement in memory consolidation similar to that produced by acute injection of 10 mg/kg. The effects on retention performance induced by the drug appear to be due to an effect on memory consolidation. They were observed when drugs were given at short, but not long, periods of time after training, i.e. when the memory trace was susceptible to modulation. Moreover, these effects are not to be ascribed to an aversive or a rewarding or non-specific action of the drugs on retention performance, as the latencies during the retention test of those mice that had not received a footshock during training were not affected by post-training drug administration. The effects of an acutely injected dose (10 mg/kg) of minaprine as well as those of a challenge dose (5 mg/kg) of the drug administered to repeatedly treated animals were reversed by pretreatment with either selective D1 or D2 dopamine receptor antagonists SCH 23390 and (-)-sulpiride administered at per se non-effective doses (0.025 and 6 mg/kg, respectively), thus suggesting that D1 and D2 receptor types are similarly involved in the effects of minaprine on memory consolidation. These results show that minaprine improves memory consolidation and that repeated drug administration leads to potentiation of this effect. Moreover, the effects of minaprine on memory consolidation are related to its dopaminergic action.