Fine structure of GABAergic neurons and synapses in the human dentate gyrus.

Surgical tissue samples of the human dentate gyrus were immunostained for glutamate decarboxylase (GAD), the gamma-aminobutyric acid (GABA)-synthesizing enzyme, and studied by both light and electron microscopy. Immunoreactive neurons and terminals displayed similar morphological characteristics as known from studies in laboratory animals. Thus, GAD-positive neurons prevailed in the hilar region, whereas immunoreactive terminals were most frequently observed in the granular layer forming symmetric synaptic contacts with dendrites, cell bodies and axon initial segments of granule cells.