Effects of oxytocin on behaviour and memory in rats subjected to chronic restrained stress.

We studied whether 21 days of restraint chronic stress would affect the contextual fear conditioning, a memory task with hippocampal-dependent components and anxiety- like behavior in the open field, and to determine whether oxytocin treatment could prevent the chronic stress induced memory and emotional disturbances. Restraint-stressed rats were injected daily (21 days) with oxytocin (1 mg/kg) or saline then tested in open field (day 22) and contextual fear conditioning task (days 23-24). Our data demonstrate that chronic restraint stress induces some behavioural changes in both saline-treated and oxytocin-treated animals. Particularly, in the open field the animals both groups were characterized by hyper-locomotion. However, oxytocin-treated animals spent more time in the inner area of the open field, which indicates to decreased anxiety- related behaviour in oxytocin-treated animals versus the saline-treated ones. In additional restraint stress decreased freezing reaction to context, irrespective of whether oxytocin was given or not. Our findings indicate that during stress OT may be involved in the regulation of emotional behavior and memory via different ways. The elucidation of corresponding mechanisms is of great importance.