Target specific organization and neuron types of the dog pelvic ganglia: Aretrograde-tracing and immunohistochemical study

The major pelvic ganglion in both the rat and guinea pig has been extensive ly studied because of its anatomical simplicity. To clarify the target spec ific neural pathway in the diffusely distributed pelvic ganglia of larger a nimals, the pelvic plexus of the female dog was investigated by retrograde tracing and immunohistochemistry. The whole mount staining of the pelvic pl exus with acetylcholinesterase histochemistry revealed 70-100 ganglia of va rying sizes. Neurons retrogradely labeled from the rectum were mainly found in ganglia located in the dorso-caudal part of the plexus. The majority of these were non-catecholaminergic, immunoreactive for either calbindin (Cal b) or neuropeptide Y (NPY), and characteristically associated with baskets of enkephalin (ENK)-immunoreactive varicose fibers. Neurons projecting to t he utero-vaginal walls were distributed in ganglia located in the ventro-ca udal part of the plexus. These mainly consisted of two major neuron groups: catecholaminergic Calb-immunoreactive neurons, and non-catecholaminergic n eurons containing nitric oxide synthase (NOS) and/or vasoactive intestinal peptide (VIP), which were preferentially associated with a network of ENK-i mmunoreactive varicose fibers. Neurons retrogradely labeled from the urinar y bladder mainly occurred in ganglia located around the junction between th e ureter and the bladder. These consisted of catecholaminergic Calb neurons and noncatecholaminergic neurons containing Calb or NOS. Only a few ENK-im munoreactive fibers were found within the clusters of catecholaminergic neu rons. These results indicate that organ specific neurons are located in sep arate ganglia and have both a distinctive composition of neuron types as we ll as different innervation by preganglionic fibers.