Involvement of D1/D2 Receptors on 1-Methyl-Β-Carboline (Harmane) Induced-Amnesia in the Step-Down Passive Avoidance Test

A number of β-carboline alkaloids such as harmane are naturally present in the human food chain. In the present study the involvement of dopaminergic system on harmane induced-amnesia was investigated. One-trial step-down paradigm was used for the assessment of memory retention in adult male NMRI mice. Intraperitoneal (i.p.) administration of harmane (5 and 10 mg/kg) immediately after training, dose-dependently decreased memory formation. Administration of D1/D2 receptors agonist, apomorphine (0.5 and 1 mg/kg, i.p.) before testing by itself could not alter memory retrieval. On the other hand, in the animals in which memory formation was impaired due to harmane post-training administration, pre-test administration of apomorphine (0.5 and 1 mg/kg, i.p.) 24 hr after training in day’s test restored memory. Furthermore, administration of SCH23390 (0.025, 0.05 and 0.1 mg/kg, i.p.) or sulpiride (12.5, 25 and 50 mg/kg, i.p.) before testing by itself could not alter memory retrieval, respectively. On the other hand in the animals in which memory formation was impaired due to harmane post-training injection, pre-test administration of SCH23390 (0.05 and 0.1 mg/kg) or sulpiride (25, 50 mg/kg, i.p.) 24 hr after training in day’s test decreased hamane-induced amnesia. These findings indicat the involvement of D1/D2 receptors in harmane induced-amnesia through different mechanism(s).