Differential regulation of striatal dopamine D-1 and D-2 receptors in acute and chronic parkinsonian monkeys

The contribution of the duration of the striatal dopamine (DA) depletion an d the expression of parkinsonian signs to changes in D-1 and D-2 receptor n umber was investigated in the present study. Some animals (N = 4) received large doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) over sho rt periods of time and were symptomatic for a short period of time (1-3 mon ths; acute parkinsonian group). Other animals (N = 4) received escalating d oses of MPTP over long periods (up to 13 months) and remained symptomatic f or an extended period (> 8 months; chronic parkinsonian group). Despite sim ilar symptomatology and similar degrees of striatal DA denervation, only ac ute parkinsonian animals had significantly increased numbers of D-1 recepto rs in most striatal regions. Striatal D-2 receptor binding was elevated in acute parkinsonian monkeys but only in some lateral striatal subregions at mid and caudal levels. These findings further suggest that the duration of parkinsonism is a critical factor in modulating changes in striatal neuroch emistry. (C) 1999 Published by Elsevier Science B.V. All rights reserved.