©2003, European Journal of Histochemistry

A number of immunocytochemical studies have indicated the presence of cholinergic neurons in the cerebral cortex of various species of mammals. Whether such cholinergic neu-rons in the human cerebral cortex are exclusively of subcor-tical origin is still debated. In this immunocytochemical study, the existence of cortical cholinergic neurons was investigated on surgical samples of human parietal associa-tion neocortex using a highly specific monoclonal antibody against choline acetyltransferase (ChAT), the acetylcholine biosynthesising enzyme. ChAT immunoreactivity was detect-ed in a subpopulation of neurons located in layers II and III. These were small or medium-sized pyramidal neurons which showed cytoplasmic immunoreactivity in the perikarya and processes, often in close association to blood microvessels. This study, providing demonstration of ChAT neurons in the human parietal neocortex, strongly supports the existence of intrinsic cholinergic innervation of the human neocortex. It is likely that these neurons contribute to the cholinergic inner-vation of the intracortical microvessels. Key words: human cerebral cortex, cholinergic neurons, microvessels, choline acetyltransferase, immunocytochemistry