Localisation of calcitonin gene-related peptide immunoreactivity within the spinal nucleus of the genitofemoral nerve

Abstract

Because transection of the genitofemoral nerve (GFN) prevents inguino-scrotal testicular descent, we postulated that a neuro-transmitted may act as a “second messenger” for androgen to cause gubernacular migration. Immunohistochemistry for various neuropeptides was performed on frozen serial sections of upper lumbar spinal cord and pelvis from immature male and female rats and immature male, female, and testicular feminisation syndrome (TFM) mice. Calcitonin gene-related peptide (CGRP) immunoreactivity was present in significant amounts in the soma of motor neurons in the 1st and 2nd lumbar segments. Vasoactive intestinal peptide, 5-hydroxytryptamine, somatostatin 8, met-enkephalin, substance P, thyrotrophin releasing hormone, and neuropeptide Y were not present above background levels in upper lumbar motor neurons. Colocalisation studies, combining fluorescent retrograde labelling of the GFN with immunohistochemistry for CGRP, showed that the CGRP staining was localized within the motor nucleus of the GFN. Quantification in mice of cells within this nucleus that contained CGRP immunoreactivity showed that the nucleus of the GFN contained more numerous and larger cells in male mice than in TFM or female mice. The proportion of cells that were positive for CGRP immunoreactivity was greatest in males, suggesting that sexual dimorphism of CGRP may be important in gubernacular migration and inguino-scrotal testicular descent.