The heterogeneity of the mesostriatal dopaminergic system as revealed in normal and parkinsonian monkeys.

The present immunohistochemical study has shown that the mesostriatal DA system in primates is a highly heterogeneous entity composed of several subsystems displaying variable degrees of vulnerability to MPTP. These subsystems were shown to affect the expression of neuropeptide in the striatofugal neurons in a manner that varies according to the location of the cell bodies in the various striatal territories. Also, a distinct subset of DA neurons in the SN/VTA complex was found to specifically innervate GPi and to be relatively resistant to the neurotoxic effect of MPTP. Furthermore, DA neurons expressing calbindin were found to be much less severely affected than other DA neurons in the SN/VTA complex of PD monkeys. Therefore, in contrast to the situation in other neurodegenerative disorders, such as Alzheimer's and Huntington's diseases, calbindin can be used as a marker for a specific subpopulation of DA neurons that are less prone to degeneration in Parkinson's disease.