NADPH-diaphorase-positive neurons in primate cerebral cortex colocalize with GABA and calcium-binding proteins.

Neurons in the monkey cerebral cortex containing nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) can be divided into two distinct types, both nonpyramidal. Type I neurons have a large soma (diameter 20-50 microm), a dense NADPH-d histochemical reaction, and are distributed throughout the cortex, but mainly in the subcortical white matter, and are mostly aspiny. Type II cells have a small soma ( Together with previous observations that almost all cortical NADPH-d cells in various subprimates are like type I cells, we suggest that type II cells may form a group of NADPH-d-rich neurons differentiated in higher mammalian cortex from a subpopulation of calbindin-containing GABAergic interneurons, and these nitric oxide-synthesizing cells may play a role in control of intracortical neuronal activity characteristic of higher cerebral functions in advanced mammals.