Capsaicin restores gubernacular contractility in TS rats

Background/Purpose: Calcitonin gene-related peptide (CGRP) may stimulate gu bernacular migration during testicular descent by release from the genitofe moral nerve (GFN). The origin of CGRP within the nerve, however, is controv ersial. This study examines whether sensory nerve destruction alters gubern acular contractility in vitro in Sprague-Dawley (SD) and congenitally crypt ochid (TS) rats. Methods: Part 1: Twenty-four SD and 16 TS rats (day 0) had either both GFNs transected or sham operation. Gubernacula were removed on day 2 and cultur ed with or without CGRP (714 nmol/L). Contractility was recorded by video. Part 2: Twenty-two SD and 17 TS rats (day 0) were injected with either caps aicin or vehicle. Gubernacula were removed (day 2) and cultured as above. Results: Part 1: In sham-operated SD rats gubernacular contracility increas ed from 8% to 83% with added CGRP. After GFN transection contractility was not affected by CGRP (21% without and 86% with CGRP; not significant). TS r at gubernacula had no endogenous contractions, but after GFN transection, t he contractile response to CGRP increased from 6% to 44% (P = .04). Part 2: In vehicle-treated SD rats, rhythmic contractions increased from 10% to 86 % with CGRP which was unchanged by capsaicin treatment (82%; not significan t). In vehicle-treated TS rats, gubernacular contractions were 6% after CGR P After capsaicin pretreatment, contractions increased to 59% with CGRP (P = .002). Conclusions: Results of this study show that chemical destruction of sensor y nerves restores gubernacular contractility in mutant cryptorchid TS rats. Release of CGRP appears to occur through sensory nerves. J Pediatr Surg 34 :1769-1772. Copyright (C) 1999 by W.B. Saunders Company.