MAPPING OF THE BASAL FOREBRAIN CHOLINERGIC SYSTEM OF THE DOG - A CHOLINE-ACETYLTRANSFERASE IMMUNOHISTOCHEMICAL STUDY

In an effort to produce a canine model of basal forebrain ischemia wit h memory deficits, we have shown that dogs possess a medial striate ar tery that perfuses basal forebrain territory, homologous to the human recurrent artery of Heubner. In the present study, we set out to delin eate the precise topography of the cholinergic neurons in the canine f orebrain, a neuronal system implicated in cognitive and memory functio ns. Floating coronal sections, derived from the head of the caudate nu cleus to the rostral border of the hippocampus, were stained for choli ne acetyltransferase using a monoclonal antibody. Representative secti ons from one dog brain were drawn. These outlines were used for measur ement of cell density, cell size, number of processes, and cell roundn ess. Choline acetyltransferase-positive neurons constituted four major subdivisions within the basal forebrain. A relatively dense populatio n of cholinergic neurons was present in the medial septal nucleus (Ch1 ). A continuum of densely packed cells was also delineated within the vertical (Ch2) and horizontal (Ch3) nuclei of the diagonal band of Bro ca. A fourth group of heterogeneously packed cholinergic neurons repre sented the nucleus basalis magnocellularis (Ch4). Except for the cauda l component of the Ch4 population, the forebrain cholinergic corticope tal system was located within the perfusion territory of the medial st riate arteries. The Ch4 cell group in dogs is better defined than that of rodents but is not as sharply demarcated as in human and nonhuman primates. Our findings indicate that the dog may serve as an excellent model for assessing neurological and memory deficits, which, in human s, results from hypoperfusion of the recurrent artery of Heubner. (C) 1996 Wiley-Liss, Inc.