Sympathetic efferent pathways projecting to the bladder neck and proximal urethra in the rat

The sympathetic innervation of the rat bladder neck and proximal urethra (BN/PU) was investigated by measuring BN/PU pressure responses to electrical stimulation of a left lumbar splanchnic nerve (LSN) following consecutive transections of more distal nerves. L2-L6 LSN stimulation increased BN/PU pressure. BN/PU pressure responses did not change after section of the right hypogastric nerve (HGN) but significantly decreased after subsequent sectioning of the commissural branches (CB-MPG) between the right and left major pelvic ganglia (MPG) (22%) and the commissural branches (CB-APG) between right and left accessory pelvic ganglia (APG) (30%). In other animals BN/PU pressure responses were slightly decreased (< 11%) after sectioning the left HGN and then significantly decreased by subsequent sectioning of the CB-MPG (< 21%) and CB-APG (< 36%). BN/PU pressure responses were decreased by sectioning the branches from the MPG to the APG (25%) or postganglionic nerves (MPG-PN) from the MPG to the BN/PU (37%). When the HGN on one side and all branches from the MPG on the contralateral side except for the CB-MPG were transected, increases in BN/PU intraluminal pressure were still elicited by LSN stimulation but were eliminated by transection of the CB-MPG. These results indicate that the left lumbar sympathetic pathway to the BN/PU passes through multiple crossing points at the level of the inferior mesenteric ganglion, MPG and APG and that this pathway could maintain closure of the internal urethral sphincter following various unilateral neural injuries.