Selective vulnerability of pigmented dopaminergic neurons in Parkinson's disease.

From a neuropathological point, the diagnosis of Parkinson's disease is confirmed by a neuronal cell loss and the presence of Lewy bodies in the substantia nigra. In Parkinson's disease, the precise type of nigral neuron which degenerate still remains unknown. Are all types of neuron similarly injured, are only subpopulations of neurons vulnerable? In an attempt to answer the question, a qualitative and quantitative analysis of the distribution of dopaminergic cells, as identified by immunohistochemistry with a specific antibody against tyrosine hydroxylase, was performed in the ventral mesencephalon of control subjects and patients who died with a clinical diagnosis of Parkinson's disease. In control brains, two types of catecholaminergic neurons were evidenced; some contain visible-neuromelanin, others do not. In patients with Parkinson's disease, the tyrosine hydroxylase positive cells which contained the pigment were the most vulnerable.