DIFFERENT EFFECTS OF REPEATED STRESSFUL EXPERIENCES ON MESOCORTICAL AND MESOLIMBIC DOPAMINE METABOLISM

The effects of repealed stressful experiences (10 min restraint, daily ) on the levels of dopamine and metabolites in the nucleus accumbens s epti and frontal cortex were evaluated. In naive mice, restraint stres s increased 3-4-dihydroxyphenylacetic acid, homovanillic acid, and 3-m ethoxytyramine levels in the nucleus accumbens and 3-4-dihydroxyphenyl acetic acid levels in the frontal cortex. The effects of stress on 3-m ethoxytyramine and homovanillic acid levels in the nucleus accumbens s epti disappeared within five days of daily restraint experiences and t he increase in 3-4-dihydroxyphenylacetic acid levels was no longer evi dent by the 10th day. By contrast, the response of mesocortical dopami ne system to restraint (increased 3-4-dihydroxyphenylacetic acid level s) was unaffected by either five or 10 days of exposure to the stresso r. Moreover, 10 min of restraint were still able to increase 3-4-dihyd roxyphenylacetic acid levels in the frontal cortex of mice repeatedly exposed (nine days) to 120 min restraint. These results indicate that the mesolimbic and the mesocortical dopamine systems adapt differently to repeated exposure to a stressor. Copyright (C) 1996 IBRO. Publishe d by Elsevier Science Ltd.