Dorsal hippocampal dopamine receptors are involved in mediating ethanol state-dependent memory

In the present study.. the effects of bilateral injections of dopaminergic agents into the hippocampal CA1 regions (intra-CA1) on ethanol (EtOH) state-dependent memory were examined in mice. A single-trial step-down passive avoidance task was used for the assessment of memory retention in adult male NMRI mice. Pre-training intra-peritoneal (i.p.) administration of EtOH (0.25, 0.5 and 1g/kg) dose dependently induced impairment of memory retention. Pre-test administration of EtOH (0.5 g/kg)-induced state-dependent retrieval of the memory acquired under pre-training EtOH (0.5 g/kg) influence. Intra-CA1 administration of the dopamine D, receptor agonist, SKF 38393 (0.5, 1 and 2 mu g/mouse) or the dopamine D, receptor agonist, quinpirole (0.25, 0.5 and 1 mu g/mouse) alone cannot affect memory retention. While, pre-test intra-CA1 injection of SKF 38393 (2 mu g/mouse, intra-CA1) or quinpirole (0.25, 0.5 and 1 mu g/mouse, intra-CA1) improved pre-training EtOH (0.5 g/kg)-induced retrieval impairment. Moreover, pre-test administration of SKF 38393 (0.5, 1 and 2 mu g/mouse, intra-CA1) or quinpirole (0.5 and 1 mu g/mouse, intra-CA1) with an ineffective dose of EtOH (0.25 g/kg) significantly restored the retrieval and induced EtOH state-dependent memory. Furthermore, pretraining injection of the dopamine D, receptor antagonist, SCH 23390 (4 mu g/mouse), but not the dopamine D-1 receptor antagonist, sulpiride, into the CA1 regions suppressed the learning of a single-trial passive avoidance task. Pre-test intra-CA1 injection of SCH 23390 (2 and 4 mu g/mouse, intra-CA1) or sulpiride (2.5 and 5 mu g/mouse, intra-CA1) 5 min before the administration of EtOH (0.5 g/kg, i.p.) dose dependently inhibited EtOH state-dependent memory. These findings implicate the involvement of a dorsal hippocarnpal dopaminergic mechanism in EtOH state-dependent memory and also it can be concluded that there may be a cross-state dependency between EtOH and doparnme. (c) 2006 Elsevier Inc. All rights reserved.