Evidence of active microglia in substantia nigra pars compacta of parkinsonian monkeys 1 year after MPTP exposure

Inflammatory changes have been found in Parkinson's disease, in humans intoxicated with the parkinsonian toxin MPTP, and in animal models of the disease. However, it is still not known whether inflammatory changes are responsible for active nerve cell death or if they have a protective role against neurodegeneration. In this study, we analyzed the glial reaction in the substantia nigra pars compacta (SNpc) and the striatum of monkeys rendered parkinsosian by chronic MPTP injections. At postmortem examination 1 year after the last MPTP injection, the density of astroglial cells and activated microglial cells in the SNpc, but not in the striatum, of MPTP-intoxicated animals was significantly higher than in the two control animals. These data suggest that neurodegeneration was still active despite the absence of the agent triggering cell death and that the glial reaction is associated with long-term neurodegeneration.

Circadian determinations of cortisol, prolactin and melatonin in chronic methyl-phenyl-tetrahydropyridine-treated monkeys

The aim of this study was to investigate whether prolactin, melatonin and cortisol are altered in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys and if so, whether MPTP may alter the availability of these hormones in chronic experimental parkinsonism. Furthermore, vegetative and sleep disorders have been described in both parkinsonian patients and in MPTP chronic monkeys; these may result indirectly from concomitant hormonal variations. Seven adult male cynomolgus monkeys were used for this experiment. Five were treated with systemic doses of intravenous MPTP but not with L-DOPA or dopaminergic agonists. In their 3rd year of parkinsonism, plasma samples were obtained day and night at 3-hour intervals. Sample collection was repeated three times for each animal. Prolactin, melatonin and cortisol concentrations were determined by enzyme immunoassay and compared with samples taken from the control group. Both MPTP-treated monkeys and the control group displayed a similar secretion pattern for the three hormones, except at several specific times when prolactin and melatonin showed significant differences. No changes were found for cortisol. The results suggest a possible alteration of hormonal metabolism in chronic MPTP parkinsonian monkeys.