Impact of Dopamine D1 Receptors of the Dorsal Hippocampus on Improving Effect of Nicotine in Ethanol-Induced Amnesia

Ethanol and nicotine increase dopamine release in different parts of the brain such as the nucleus accumbens and the hippocampus. Dopamine D1 receptors have been detected in dorsal hippocampus known as a key brain region that seems to mediate some behavioral effect of ethanol and nicotine. The present study was carried out to determine the influence of dopamine D1 receptors of dorsal hippocampus as to the effect of Nicotine on ethanol-induced amnesia. In this experimental study, 192 adult male NMRI mice were anaesthetized and cannulae implanted bilaterally in the CA1 regions of the dorsal hippocampus using stereotaxic method. Seven days after recovery from surgery, the behavioral testing was started using inhibitory avoidance task. In this study, ethanol, nicotine and SCH23390 (D1 receptor antagonist) were used. Pre-training or pre-test injection of ethanol induced amnesia (P<0.001). The amnesia induced by pre-training ethanol restored with pre-test administration of same doses of ethanol (P<0.001). Pre-test injection of nicotine restored amnesia induced by pre-training ethanol (P<0.001). Pre-test intra-CA1 injection of SCH23390 by itself impaired memory and prevented the nicotine reversal effect on ethanol- induced memory impairment (P<0.001). These results suggest that dopamine D1 receptor of dorsal hippocampus may play an important role in improving effect of nicotine on the ethanol-induced amnesia.