Demonstration of preganglionic fibers in the inferior mesenteric ganglion, pelvic ganglia and related nerves of the guinea pig by anterogradely transported wheat germ agglutinin-horseradish peroxidase conjugate.

Preganglionic sympathetic neurons in the guinea pig were labeled by injections of wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) into the L2 and L3 spinal cord segments. After anterograde transport of the tracer the following areas were examined for the presence of HRP-labeled fibers: the inferior mesenteric ganglion (IMG), the pelvic ganglia, the hypogastric and colonic nerves. In the ganglia labeling appeared predominantly as clusters of varicose-like profiles suggestive of being axon terminals. Particularly in the pelvic ganglia, these profiles appeared to surround the contours of some of the ganglion cell bodies. Numerous HRP-positive fibers were present in the hypogastric nerves, but only occasional fibers were observed in the colonic nerves. The pattern of labeling differed markedly from that described previously after anterograde transport of WGA-HRP in sensory fibers of the IMG, hypogastric and colonic nerves. Furthermore, the results from this and the previous study show that anterograde tracing with WGA-HRP can be a useful means for analyzing the structural organization of various fiber inputs to autonomic ganglia.