Investigating the Effects of Tolcapone a Catechol-O-Methyltransferase Inhibitor on Learning and Memory in Passive Avoidance Task

Aim: The aim of the present study was to evaluate the effects of tolcapone in haloperidol-challenged rodent models of learning and memory and reserpine-induced parkinsonism in rats.

Methods: The learning and memory enhancing effects of tolcapone (TCP) were assessed in male Wistar rats treated with 5, 15 and 30 mg/kg bw, p.o. The impact of tolcapone on haloperidol challenge and reserpine induced parkinsonism was studied in rodents treated with 5,15 and 30 mg/kg bw TCP p.o. Step-through passive avoidance and loco-motor activity were assessed. The latency reaction time and the number of horizontal and vertical movements were registered, respectively. Statistical analysis was done by SPSS Statistics 19.

Results: Tolcapone in all studied doses increased latency in short- and long-term memory tests as well as the number of movements in the horizontal and vertical plane. The rats treated with haloperidol and tolcapone in all studied doses showed significant increase in latency during the training days and the two retention tests when compared with the haloperidol treated control but not with saline. In rats with the reserpine model of parkinsonism there was not significant difference in latencies between experimental and saline treated groups neither during the learning session nor during both memory retention tests.

Conclusion: Tolcapone improves incidental memory and delayed recall memory in hippocampus dependent step-through passive avoidance task. The observed effects are probably dopamine mediated but hippocampal noradrenaline might also play an important role.