Immunohistochemical Characteristics of Neurons in the Substantia Nigra of the Human Brain

Objectives. To identify the cytochemical chromosomes of structurally unaltered neurons in the substantia nigra of the human brain using a wide spectrum of immunocytochemical markers, some of which (glutamate decarboxylase 65, PGP 9.5, unphosphorylated neurofilament proteins, α-tubulin) have not previously been used in studies of dopaminergic neurons in humans. Materials and methods. The study used fragments of human midbrain (17 men and women aged 28–78 years) obtained from the archive of the Department of General and Special Morphology, Institute of Experimental Medicine. Studies were performed using classical neurohistology and immunocytochemistry methods using antibodies to 15 different proteins. Results. Most neurons in the substantia nigra were characterized by decreased expression of general neuronal markers – nuclear protein NeuN, protein PGP 9.5, and neuron-specific enolase. The substantia nigra was not found to contain GABAergic (GAD65-immunopositive) neurons. The dorsal part of this area contained occasional cholinergic neurons not containing neuromelanin. Calcium-binding proteins calbindin and calretinin were absent from most nigral cells, though the dorsal part of the substantia nigra contained occasional calbindin-containing neurons, while the ventral part contained occasional calretinin-containing neurons. Nitric oxide synthase was present in both the neuropil and neuron bodies in the substantia nigra. Conclusions. The data obtained here provide evidence of the unique cytochemical properties of nigral neurons, which may be associated with their increased predisposition to degeneration.