HUMAN AND MONKEY CHOLINERGIC NEURONS VISUALIZED IN PARAFFIN-EMBEDDED TISSUES BY IMMUNOREACTIVITY FOR VACHT, THE VESICULAR ACETYLCHOLINE TRANSPORTER

The predicted C-terminal dodecapeptide of the human vesicular acetylch oline transporter (VAChT), deduced from the unique open reading frame of the recently cloned human VAChT cDNA, was conjugated through an N-t erminal cysteine to keyhole limpet hemocyanin and used as an immunogen to generate polyclonal antihuman VAChT antibodies in rabbits. The dis tribution of the VAChT antigen in representative regions of the cholin ergic nervous system was examined and compared to that of the acetylch oline biosynthetic enzyme choline acetyltransferase (ChAT), a specific marker for cholinergic neurons. VAChT immunoreactivity was localized in cell bodies of neurons in the basal forebrain and ventral horn of t he spinal cord, regions in which major cholinergic projection systems to the cerebral cortex and to skeletal muscle, respectively, originate . The primate caudate nucleus contained numerous VAChT-positive intern eurons. VAChT immunoreactivity was visualized in both cell bodies and extensive terminals in striatal interneurons, in contrast to formalin- fixed, deparaffinized sections stained for ChAT, in which cell bodies and fibers were stained but nerve terminals were less well visualized than with the VAChT antiserum. VAChT-positive nerve fibers were visual ized in routinely immersion-fixed, paraffin-embedded human cerebral co rtex, comparable to the density of fibers observed in perfusion-fixed Bouin's-postfixed monkey cerebral cortex. Extensive investment of virt ually all principal ganglion cells of thoracic sympathetic ganglia of monkey and human with VAChT-positive nerve terminals was observed. VAC hT-positive cell bodies, presumably corresponding to cholinergic sympa thetic sudomotor neurons, were a significant fraction of the total pri ncipal cell population in monkey and human thoracic sympathetic gangli a. VAChT is a specific marker for cholinergic neurons in human and rhe sus monkey, visualizing especially nerve terminals more extensively th an antibodies against the cholinergic biosynthetic enzyme ChAT, in rou tinely fixed tissue. VAChT immunoreactivity in cholinergic nerve termi nals of the central and peripheral nervous systems ought to prove usef ul for visualizing cholinergic synapses and neuroeffector junctions, a nd their functional status during development and in neurodegenerative and autonomic disease.