[Effect of a cyclic analog of enkephalin on learning and memory in the mouse]

In experiments on mice, the effect of cyclic analogue of enkephalin (CAE) on the processes of learning and memory was studied in control animals and in animals with changed functional state of monoaminergic brain systems. Administration of the peptide to intact animals significantly accelerated the acquisition of conditioned reflexes of two-way avoidance and did not significantly affect the retention of these reflexes and their subsequent reproduction. Retention and reproduction of conditioned reflexes elaborated in one combination, was disturbed. Administration of iprazid did not eliminate the "accelerating effect" of CAE on the formation of conditioned reflexes of the two-way avoidance but sharply disturbed their retention. In such conditions, the amnesing iprazid effect increased still more. Besides, under CAE effect, the activity of acetylcholinesterase in the motor and especially in the visual cortex of the mice increased. The obtained data testify to an important role of the monoaminergic and cholinergic brain mechanisms in realization of CAE effects on the processes of learning and memory.