DIFFERENT EFFECTS OF OPIATE WITHDRAWAL ON DOPAMINE TURNOVER, UPTAKE, AND RELEASE IN THE STRIATUM AND NUCLEUS-ACCUMBENS

The purpose of these experiments was to further characterize changes i n dopaminergic function that follow withdrawal from chronic opiate tre atment. Withdrawal after treatment to a maximum dose of 120 mg/kg of m orphine did not alter dopamine concentrations in the substantia nigra, ventral tegmental area, striatum, or nucleus accumbens; but did decre ase concentrations of DOPAC and the ratio of DOPAC to dopamine in the lateral striatum and nucleus accumbens. Uptake of tritiated dopamine w as diminished for withdrawn slices obtained from the striatum with no effect observed for tissue from the nucleus accumbens. Deficits of in vitro release of tritiated dopamine also occurred following withdrawal , with the nucleus accumbens being sensitive to dependence produced by a lower dose of morphine. In conclusion, opiate withdrawal produces a complex pattern of effects on dopaminergic function that is specific for the striatum and nucleus accumbens.