Neurons with choline acetyltransferase immunoreactivity and mRNA are present in the human cerebral cortex

We examined the cerebral cortex of five autopsied individuals without neuro logical and psychiatric diseases by immunohistochemistry using an anti-huma n recombinant choline acetyltransferase (ChAT) polyclonal antibody and in s itu hybridization with S-35-labeled human ChAT riboprobes. The immunohistoc hemistry detected positive neurons which were medium-sized or large pyramid al neurons located predominantly in layers III and V. The density of such n eurons was higher in the motor and secondary sensory areas than in other co rtical areas; the immunoreactive neurons in layer V were more densely distr ibuted in the motor area and those in layer III were distributed in the sec ondary sensory areas. Positively stained, non-pyramidal neurons were observ ed in the superficial layer of the cingulate gyrus and parahippocampus. No immunoreactive neurons were found in the primary sensory areas. The in situ hybridization detected some neurons with signals for ChAT mRNA in the cere bral cortex, most of which were distributed in layer V of the motor area an d in layer III of the secondary visual area. These results indicate that th e human cerebral cortex contains cholinergic neurons and displays regional and laminal variations in their distribution.