ACETYLCHOLINE INNERVATION OF SENSORY AND MOTOR NEOCORTICAL AREAS IN ADULT CAT - A CHOLINE-ACETYLTRANSFERASE IMMUNOHISTOCHEMICAL STUDY

Light microscopic choline acetyltransferase (ChAT) immunocytochemistry was used to examine the distribution of the acetylcholine innervation in primary motor (4 gamma) and sensory (3a, 3b, 41 and 17) cortical a reas of adult cat. In every area, scattered immunoreactive cell bodies were present and a relatively dense meshwork of ChAT immunoreactive a xons pervaded the whole cortical thickness. These axons were generally thin and bore innumerable varicosities of different sizes. A few thic ker and smoother fibers and occasional clusters of unusually large var icosities were also visible. Overall, area 17 was less densely innerva ted than the other areas. In each area, layer I showed the densest inn ervation. Innervation of underlying layers was rather uniform in area 17, but patterned in other areas. In areas 4 gamma and 3a, layers II, upper III and V showed preferential innervation. Innervation of layer IV was the strongest in areas 3b and 41. Area 3a was transitional betw een 4 gamma and 3b. Except in area 17, the laminar pattern of acetylch olinesterase staining was consistent with that of ChAT. In the light o f current data on the distribution of this cortical innervation in dif ferent species, and of its presumed ultrastructural features, it appea rs likely that such regional and laminar features subtend widespread, modulatory roles of ACh.