[Nitroxidergic neurons in the white matter of the human hippocampal formation].

Distribution of nitric oxide synthase in hippocampal formation of 4 human subjects was studied using histochemical NADPH-diaphorase reaction. Two cell types (spinous and non-spinous) were distinguished. Type 1 neurons exhibit morphological features of pyramidal cells: their apical and basal dendrites are thickly covered spines throughout entire length. It is admissible that these cells are ectopic pyramidal neurons by their origin and function as acceptors of septal and associative and commissural afferents transmitted to hippocampus. Type 2 cells are morphologically heterogeneous with dipolar, multipolar and round neurons present among them. The cells are arranged either one by one or in groups, forming synaptic contacts with one another. Adjacent vessels are not only accompanied by their long varicose dendrites but are closely surrounded by their terminals. Non-spinous hippocampal neurons participate in local blood circulation by synthesizing nitric oxide--an endothelium-derived relaxation factor.