Fluorescent anterograde labelling of the genitofemoral nerve shows that it supplies the scrotal region before migration of the gubernaculum

Abstract

The genitofemoral nerve (GFN) contains a sexually dimorphic neuropeptide transmitter, calcitonin generelated peptide (CGRP). It has been proposed that release of CGRP from the nerve may mediate testicular descent. The aim of this study was to determine the course of the GFN in order to see if CGRP-containing fibres reached the future scrotum before gubernacular migration occurs, since this arrangement would be expected if the nerve controls gubernacular migration by CGRP release. Fluorescent anterograde labelling of the cut GFN in young rats using diamidinophenyl indole (DAPI) or Fast Blue was performed to determine the distal course of the nerve. On frozen serial sections, the nerve was found running posterolateral to the developing spermatic cord in the inguinal canal, then distally on the surface of the cremaster muscle. It then turned cranially to enter the gubernaculum from its distal attachment while some branches continued past the gubernaculum to end in the skin of the future scrotum. Immunoperoxidase staining for CGRP showed labelling in all GFN fibre bundles, including those reaching the scrotum. The course of the nerve with its sexually dimorphic neurotransmitter, CGRP, suggests that the nerve may influence the direction of gubernacular migration from the groin into the scrotum.