The effects of testicular denervation on spermatogenesis in the Sprague-Dawley rat

In the rat, regression of spermatogenesis during the chronic stages of spin al cord injury (SCI) occurs in the presence of normal function of the pitui tary-testis hormone axis, thus suggesting that nonendocrine mechanisms migh t be involved. The current study examined whether disruption of neural inpu t to the testis contributes to the cascade that leads to the regression of spermatogenesis. Four weeks after denervation of the superior spermatic ner ve (SSN), testis weight was 25% lower (p < 0.01) than that of the contralat eral sham-operated testis. Defects in spermatogenesis including phagocytosi s of mature spermatids, vacuolization of spermatid nuclei, delayed spermiat ion and incomplete cellular associations were observed in >60% of the tubul es. In the remaining 30-40% of tubules, the seminiferous epithelium was sev erely regressed. While cutting the inferior spermatic nerve (ISN) alone did not affect spermatogenesis significantly, it enhanced the effect of SSN de nervation on both spermatogenesis and testis weight (p < 0.01). Spermatogen esis was totally regressed in the SSN/ISN-denervated testes. At this time, quantitatively normal spermatogonial proliferation was maintained in SSN- o r ISN-denervated testes. Twelve weeks after surgery, regression of the semi niferous epithelium characterized by absence of proliferating spermatogonia , while undifferentiating spermatogonia were present, was observed in all S SN-denervated testes. Ar this time, regression of the seminiferous epitheli a also occurred in >30% of the tubules in ISN-denervated testes. At both ti mes, serum follicle-stimulating hormone, luteinizing hormone and testostero ne levels were normal and >60% of normal testicular testosterone concentrat ions were maintained in the denervated testes. These results indicate that disruption of neural input to the testis is not a cause for the decrease in spermatogonial proliferation during the acute phase of SCI, but may contri bute to the chronic effects of SCI on spermatogenesis. Copyright (C) 2000 S . Karger AG, Basel.