Increased caudate dopamine turnover may contribute to the recovery of motor function in marmosets treated with the dopaminergic neurotoxin MPTP

Abstract

Administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to common marmosets initially impaired motor function, but a partial recovery occurred over the following weeks. At both 10 days and 4–6 weeks following MPTP treatment, [ 3H]dopamine ([ 3H]DA) uptake into synaptosomal preparations of putamen was markedly decreased. At 10 days and 4–6 weeks following MPTP treatment DA, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) levels in the caudate nucleus and nucleus accumbens were substantially reduced. However, the levels of HVA and DOPAC in caudate nucleus were higher at 4–6 weeks than at 10 days. The ratio of ( DOPAC+ HVA) DA in caudate nucleus was elevated at 10 days following MPTP treatment and even more so at 4–6 weeks. No change in B max or K d values for [ 3H]spiperone binding to caudate preparations were observed. The recovery of motor function in marmosets observed following MPTP treatment may result partially from a compensatory increase in caudate DA turnover by remaining neurones.