Early Social Isolation Causing Emotional Motivational Alterations in Rats, is Accompanied by a Deficit of Short-term Habituation, but does not Affect Spatial Memory

The relationship between psycho-emotional disorders and cognitive impairments caused by early social isolation is not clear. In the present study, emotional-motivational state, habituation, and spatial memory were studied in male Wistar rats kept under social isolation for three months immediately after weaning from their mothers. After two months of social isolation we have revealed an increase in aggression in the social interaction test and anxiety in the Elevated Plus Maze, pre-pulse inhibition deficit and an increase in the amplitude of the modulated acoustic startle response in the test for sensorimotor reactivity as well as an impairment of short-term habituation by the dynamics of the acoustic startle. After three months of social isolation, aggressiveness in rats remained elevated, while an increase in anxiety was not detected. An increase in motor activity and an impairment of short-term habituation by the dynamics of locomotion in the "open field" test were found. After two and three months of social isolation, we did not reveal signs of depression in rats in the forced swimming test. After three months of isolation, the rats did not show the impairment of long-term spatial memory in the Morris Water Maze. However, we noted the peculiarities of acquisition of spatial learning to search the platform location in these animals, probably, due to the nature of their emotional response in an unfamiliar stressful situation. On the day of testing, in the absence of a platform, socially isolated rats tended to increase the number of visits, and the distance traveled in the zone adjacent to the platform during training days.