EFFERENT AND PRIMARY AFFERENT NEURAL PATHWAYS INNERVATING THE LOWER URINARY TRACT OF THE CAT

Part II Primary Afferent Neural Pathways

Abstract

Primary afferent neural pathways from the lower urinary tract were examined in the cat. To do this, horseradish peroxidase (HRP) was applied to the following 9 sites; bladder wall, bladder trigone, proximal urethra, external urethral sphincter muscle, vesical branch of the pelvic nerve, urethral branch of the pudendal nerve, hypogastric nerve, central and lateral fibers projecting to the inferior mesenteric ganglion (IMG).
The primary afferent pathway via the hypogastric nerve entered the spinal cord via the L1-5 dorsal root ganglia (DRG). This pathway crossed partially at the IMG and bilateral sympathetic chains. Other pathways via the vesical branch of the pelvic nerve and the urethral branch of the pudendal nerve entered the spinal cord mainly via the S1-3 DRG and partially via the L1-5 DRG. This pathway via the L1-5 DRG also crossed partially at the bilateral sympathetic chains.
Transganglionic fibers from the L1-5 DRG were found to project to the laminae I, IV-VII and X at the levels of caudal thoracic, lumbar and rostral sacral cord segments, and the lateral portion of the gracile nucleus in the medulla. Other fibers from the S1-3 DRG were found to project to the laminae I, IV-VII and X at the levels of middle and caudal lumbar sacral and rostral coccygeal cord segments, and the medial portion of the gracile nucleus.
These widespread rostrocaudal extents of the hypogastric, pelvic and pudendal primary afferent projections are consistent with the spinal and supraspinal integration of the sympathetic, parasympathetic and somatic elements for micturition reflexes.