Localization of calcitonin gene-related peptide within the genitofemoral nerve in immature rats

Background/Purpose: Calcitonin gene-related peptide (CGRP) has been propose d to influence migration and testicular descent by release from the genitof emoral nerve. The site of CGRP within the nerve has been controversial, wit h conflicting views on whether CGRP is synthesised and released from the mo tor nerves. Methods: The genitofemoral nerve (GFN) was retrogradely labelled by fluores cent dye (DAPI) in 25 Sprague-Dawley rats (days 5, 16, and 31, n = 8 in eac h group; day 35, n = 1), Spinal cords and dorsal root ganglia (DRG) were re moved two to three days later and sectioned far immunofluorescence. Substan ce P and CGRP-containing cells were labelled with fluorescein-linked antibo dies. Specimens were examined by double fluorescence to identify cells with both markers. Results: The motor nucleus of the GFN contained 1 19 cells on day 7 and 284 cells by days 19 through 34. A prominent band of CGRP-containing fibers, a rising from the dorsal horn, synapsed with the GFN motor nucleus itself. CG RP-labelled GFN cells were found in the DRG by double labelling. Conclusions: CGRP from the GFN may affect gubernacular migration by release from the sensory nerves, rather than motor nerves as previously thought. T he GFN motor nucleus receives CGRP-containing innervation from the dorsal h orn, which may form part of the cremasteric reflex. J Pediatr Surg 34:986-9 91. Copyright (C) 1999 by W.B. Saunders Company.