SUBSTANTIA-NIGRA PARS RETICULATA NEURONS IN PARKINSONS-DISEASE

We have examined by immunohistochemistry the parvalbumin-containing ne urons of the substantia nigra in patients with Parkinson's disease and in age-matched controls. Parvalbumin, a calcium binding protein, is i nvolved in buffering intracellular calcium and in this study was local ized within the majority of non-pigmented neurons of the human pars re ticulata. Previous studies have shown that the parvalbumin-immunoreact ive pars reticulata neurons are GABAergic and project to the motor tha lamus and tectum. Their increased output, due to the loss of dopaminer gic inhibition in Parkinson's disease, decreases cortical activation v ia thalamic pathways, causing parkinsonian symptoms. In Parkinson's di sease there was a significant loss of parvalbumin-immunoreactivity fro m these neurons, though there was no evidence of actual cell loss. Thi s loss of parvalbumin-immunoreactivity was detected only in those case s with end-stage Parkinson's disease. (C) 1996 Academic Press Limited.