Cholinergic divergent projections from rat basal forebrain to the hippocampus and olfactory bulb.

Cholinergic neurons in the basal forebrain which project to both the hippocampus and olfactory bulb were identified in the rat by using twin fluorescent retrograde tracers combined with fluorescence immunohistochemistry for choline acetyltransferase (ChAT). The majority of neurons simultaneously labeled with the two tracers were also identified as being ChAT-positive. They were located at the border between the horizontal and vertical limbs of the diagonal band of Broca. Their numbers were very small compared with neurons singly labeled from each of the projection areas.