Topography of choline acetyltransferase immunoreactive neurons and fibers in the rat spinal cord.

The topography of choline acetyltransferase immunoreactivity was studied in the rat spinal cord with a monoclonal antibody. Cholinergic fibers were most prominent in lamina III of the dorsal horn and originated from cholinergic neurons within the spinal cord. Lamina X, which was rich in cholinergic neurons and fibers, provided cholinergic interconnections between the dorsal, intermediate and ventral gray. Within the ventral gray, choline acetyltransferase immunoreactive boutons were found on motor neurons. This study suggests that the cholinergic innervation of the spinal cord arises from neurons intrinsic to the spinal cord. The cholinergic neurons within the spinal cord may provide several, overlapping levels of regulation of spinal cord neurons.