REINNERVATION AFTER DESTRUCTION OF THE DOPAMINERGIC SYSTEM IN THE RATNUCLEUS-ACCUMBENS - A QUANTITATIVE IMMUNOHISTOCHEMICAL ANALYSIS

The recurrence of dopamine-immunoreactive (DA(i)) fibers and the effec t of the adrenocorticotrophic hormone (ACTH)-(4-9) analog ORG 2766 on this process were investigated 1, 4, 12 and 24 weeks after a unilatera l 6-hydroxydopamine (6-OHDA) lesion in the nucleus accumbens (NAc). DA (i) fibers were almost completely absent I week after the lesion. A gr adual increase in DA(i) fibers throughout the NAc was observed, with s ubnormal values at 24 weeks. Treatment with ORG 2766 during the first week after the lesion resulted in more DA(i) fibers 4 weeks after the lesion as compared to placebo treatment, but not 12 and 24 weeks after the lesion. After 6-OHDA lesioning reinnervation of the NAc takes pla ce and this process is transiently facilitated by ORG 2766.