Distribution of primary afferent neurons innervating the porcine oviduct and their immunohistochemical characterization.

Previous studies have revealed that some nerve fibres supplying the porcine oviduct may be of sensory origin. Therefore, the present study was aimed at disclosing the distribution of porcine 'oviductal' primary afferent neurons and the pattern(s) of putative coincidence of substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOS) within these nerve cell bodies using combined retrograde tracing and double-labelling immunohistochemistry. We also investigated the existence and coexistence of immunoreactivities to tyrosine hydroxylase (TH) and dopamine beta-hydroxylase within the neurons because in some mammals, dorsal root ganglia (DRG) were previously found to contain perikarya immunoreactive (IR) to TH. Retrograde labelling revealed a population of large sensory neurons located in the Th(10)-L(3) DRG. There were no significant differences in the number or distribution between the ampulla- and isthmus-projecting neurons. Double-labelling immunoflourescence allowed several subpopulations of the studied perikarya to be distinguished. The largest one consisted of SP/CGRP-IR nerve cells, while the smallest subpopulation comprised NOS/VIP-IR neurons. Either SP/NOS, solely SP- or solely NOS-IR neurons were also found. Because identically coded nerve fibres have been observed within the wall of the porcine oviduct, based on their association with particular organ structures, it can be assumed that SP/CGRP-, SP/NOS- or solely NOS-IR neurons are involved in the antidromic relaxation of the oviductal vessels, SP-, NOS- or SP/CGRP-IR nerve cells control the oviductal tonus and that some neurons project beneath the epithelium and are involved in the transmission of sensory modalities from the oviduct to the spinal cord. Copyright 2000 S. Karger AG, Basel