Plasticity of extrapyramidal dopamine system in Parkinson's disease - A postmortem study

Investigating the compensatory changes developing in the course of Parkinso n's disease, we assayed the concentrations of amine neurotransmitters and t heir metabolites, and dopamine D-1 and D-2 and alpha(2)-noradrenergic recep tors in various areas of parkinsonian and control brains obtained by autops y. Those data were used to calculate the [metabolite]/[amine] and [receptor density]/[amine] ratios, regarded as measures of pre- and postsynaptic ada ptations, respectively. The metabolic rate of dopamine rose by 200-400% in all. basal ganglia; the metabolism of serotonin was elevated, by 150-200%, only in the caudate nucleus and locus coeruleus. The receptor/neurotransmit ter ratios for dopamine D-1 and D-2 receptor were augmented several-fold in the basal ganglia, but not in the nucleus accumbens. In the locus coeruleu s the dramatic decline in the noradrenaline concentration was parallel to t he decrease in alpha(2)-adrenoceptor density. The results suggest that the dopaminergic system of the parkinsonian brain shows plasticity of both pre- and postsynaptic structures that permits adaptations to the progressive lo ss of the neurotransmitter.