The segmental distribution of afferent fibers from the vaginal cervix and hypogastric nerve in rats

Injections of horseradish peroxidase-wheat germ agglutinin (HRP-WGA) into the walls of the vagina and cervix (vaginocervical injections) of rats resulted in labeling of dorsal root ganglia (DRG) cells located at T₁₁-L₄ and L₆-S₂. In a second group of animals, exposure of the hypogastric nerve to HRP-WGA resulted in a similar bimodal distribution of labeled cells as compared to vaginocervical injections. In a third group, unilateral hypogastric nerve transection prior to injection of HRP-WGA into the vaginocervical walls resulted in a significant reduction in DRG cells labeled at T₁₃, L₁, L₂, L₆ and S₁. Bilateral transection of the hypogastric nerves prior to vaginocervical injections eliminated labeled DRG cells at thoracolumbar levels but not at L₆ and S₁. Bilateral pelvic neurectomy reduced, but did not eliminate labeled DRG cells at L₆ and S₁ following vaginocervical injections. These results indicate that the hypogastric nerve constitutes a major sensory pathway from the vaginocervical walls to thoracic, lumbar and sacral levels of the spinal cord. The hypogastric nerve may subserve the transmission of noxious input from the vaginocervical walls as well as the activation of ascending spinal pathways involved in neuroendocrine reflexes during parturition.