Role of resocialization and of 5-HT1A receptor activation on the anxiogenic effects induced by isolation in the elevated plus-maze test

Rats were isolated for periods varying from 1 h to 2 weeks and the exploratory activity of these animals on the elevated plus-maze was studied. Rats isolated from periods of 2 h on displayed a significant reduction in the number of entries and time spent in the open arms of the plus-maze compared to socially housed controls. This effect was not correlated with the decrease in the total number of entries also produced by isolation. Acute treatment with midazolam or resocialization for a 24-h period clearly reversed these responses produced by prior 2-h isolation in the elevated plus-maze. It is suggested that exposure to a 2-h isolation period could be a useful nonpharmacological means of generating anxiety in laboratory rodents. Chronic treatment, but not acute treatment, with gepirone, a 5-HT1A agonist, inhibited the anxiogenic effects caused by a 2-week period of isolation. The reduction in aversiveness promoted by resocialization may be due to a recovery in the 5-HT activity depressed by isolation in a much faster way than observed with chronic gepirone administration.