Involvement of D۱/D۲ Receptors on ۱-Methyl-Β-Carboline (Harmane) Induced-Amnesia in the Step-Down Passive Avoidance Test

Background and Objective: 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. Materials and Methods: One-trial step-down paradigm was used for the assessment of memory retention in adult male NMRI mice. Results: Intraperitoneal (i.p.) administration of harmane (۵ and ۱۰ mg/kg) immediately after training, dose-dependently decreased memory formation. Administration of D۱/D۲ receptors agonist, apomorphine (۰.۵ and ۱ 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 (۰.۵ and ۱ mg/kg, i.p.) ۲۴ hr after training in day’s test restored memory. Furthermore, administration of SCH۲۳۳۹۰ (۰.۰۲۵, ۰.۰۵ and ۰.۱ mg/kg, i.p.) or sulpiride (۱۲.۵, ۲۵ and ۵۰ 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 SCH۲۳۳۹۰ (۰.۰۵ and ۰.۱ mg/kg) or sulpiride (۲۵, ۵۰ mg/kg, i.p.) ۲۴ hr after training in day’s test decreased hamane-induced amnesia. Conclusion: These findings indicat the involvement of D۱/D۲ receptors in harmane induced-amnesia through different mechanism(s).

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Keywords: Harmane , Apomorphine , SCH۲۳۳۹۰ , Sulpiride , Step-down passive avoidance task , Mice