Neuronal input from the inferior mesenteric ganglion (IMG) affects sperm transport within the rat cauda epididymis

Sympathetic nerves emanating from the inferior mesenteric ganglion (IMG) innervate the mammalian epididymis and vas deferens. We have reported previously that surgical removal of the rat IMG results in excessive accumulation of spermatozoa within the cauda epididymis. The objective of the present study was to determine whether sperm accumulation following IMG removal was due to a denervation-induced change in the rate of sperm transport within the cauda epididymis. In these studies epididymal sperm numbers were counted and used as a measure of sperm transport within the epididymis. In order to examine sperm transport within the cauda epididymis specifically, efferent duct ligation (EDL) was used to prevent further entry of testicular spermatozoa into the epididymis. Rats were divided into four treatment groups: sham-operated control, EDL alone for 7 days (EDL + 7), EDL alone for 14 days (EDL + 14), or EDL for 7 days at which time the IMG was removed and the rats were maintained for an additional 7 days (EDL + IMG). Epididymides were homogenized and the number of spermatozoa in the caput and cauda epididymis was counted. In EDL + 7 rats, the caput epididymis was devoid of spermatozoa. The rate of transit of spermatozoa through the cauda epididymis of EDL + 7 rats was approximately 3.43 million/day. The total number of cauda epididymal spermatozoa in EDL + 7 rats was reduced by 20% compared to sham-operated control rats. In EDL + 14 rats, spermatozoa transited the cauda epididymis at a rate of approximately 9.57 million/day, and the total number of spermatozoa in the cauda epididymis was reduced by 73% compared to sham-operated controls. If the IMG was removed 7 days following EDL, spermatozoa transited the cauda epididymis at a rate comparable to that observed in EDL + 7 rats (3.39 million/day). Following IMG denervation of EDL + 7 rats, cauda epididymal sperm numbers were maintained at levels observed in the EDL + 7 rats. These data demonstrate that the transport of spermatozoa through the cauda epididymis is influenced significantly by neuronal input from the IMG.