Effects of serotoninergic receptor antagonists and their combination with scopolamine on memory

Using the method for passive avoidance with punishment reinforcement (step-down), it was found that the serotonin (5-HT)-receptor blockers methergoline, methysergide and ritanserin at a dose of 5 mg/kg b.w. administered i.p. 30 min before the training session as well as the M-cholinergic-receptor blocker scopolamine administered at a dose of 2 mg/kg b.w. 90 min before training impaired acquisition and retention of memory traces. The memory impairment was also manifested by the poor habituation of methergoline- and scopolamine-treated rats placed in an unfamiliar environment. Memory deficit was increased by the combination of methergoline or ritanserin with scopolamine. On multiple administration before training the nootropic drug adafenoxate completely prevented the amnestic effect of the combination methergoline plus scopolamine.