FERTILITY OF RAT EPIDIDYMAL SPERM AFTER CHEMICALLY AND SURGICALLY INDUCED SYMPATHECTOMY

Guanethidine, a chemical that selectively blocks sympathetic noradrene rgic neurons, was used to investigate the role of sympathetic innervat ion in the fertility of rat epididymal sperm, using both natural matin g and in utero insemination protocols. This animal model correlates, a t least in part, with spinal cord injury (SCI) in men. Adult male rats were treated daily by i.p. injections, for 21 or 42 days, with 0 or 6 .25 mg/kg guanethidine. To compare the effects of guanethidine-induced sympathectomy with those following surgically induced sympathectomy, the inferior mesenteric ganglion and the proximal hypogastric nerves w ere removed in another group of rats. Both chemically and surgically i nduced sympathectomy increased the weight of the epididymis and semina l vesicles/coagulating glands as well as the number and the transit ti me of cauda epididymal sperm. Neither serum testosterone levels nor LH was affected by treatment with guanethidine. Using natural mating, no litters were produced by guanethidine-treated rats. Chemically denerv ated rats failed to produce copulatory plugs or ejaculate into the ute rus. However, distal cauda epididymal sperm from chemically or surgica lly denervated rats displayed normal fertilization ability (80%) using in utero inseminations. In addition, the sperm of denervated rats did not show abnormal sperm chromatin structure using an assay that detec ts DNA damage. We conclude that sympathectomy delays the transit of sp erm through the cauda epididymidis and produces ejaculatory dysfunctio n but does not compromise sperm quality in the distal cauda epididymid is. Moreover, these data provide compelling evidence that there is no association between the prolonged transit time of sperm within the epi didymis, i.e., pre-ejaculatory sperm aging, and the fertility of those sperm, which has important implications for artificial insemination u sing sperm from men with SCI.