Undescended testis is accompanied by calcitonin gene related peptide accumulation within the sensory nucleus of the genitofemoral nerve in trans-scrotal rats.

PURPOSE: Recent data suggest that calcitonin gene related peptide (CGRP) released from the sensory branch of the genitofemoral nerve may regulate testicular descent. We studied the number of CGRP immunoreactive cells in the sensory nucleus of the genitofemoral nerve (L1 to L2 dorsal root ganglia) in cryptorchid trans-scrotal rats. Four-week-old trans-scrotal rats with unilateral undescended testis underwent bilateral genitofemoral nerve dissection and retrograde nerve labeling with the fluorescent dye 4,6-diamidino-2-phenylindole (DAPI). Animals were sacrificed 48 hours later and the L1 to L2 dorsal root ganglia were removed. Serial sections were obtained and double fluorescent labeled with antibody to CGRP. Retrograde labeled and CGRP immunoreactive cells were counted using an epi-fluorescent microscope. In the 6 male trans-scrotal rats evaluated we noted a mean plus or minus standard deviation of 1,272 +/- 98 retrograde labeled dorsal root ganglion cells ipsilateral to a fully descended testicle, including 98 +/- 34 that were also CGRP immunoreactive. On the side of the undescended testis there was a mean of 1,600 +/- 304 DAPI positive cells and 160 +/- 51 CGRP immunoreactive, DAPI labeled cells. The difference was significant (p <0.02). This study shows that in trans-scrotal rats the sensory nucleus of the genitofemoral nerve contains more CGRP immunoreactive cells ipsilateral to an undescended testis than on the contralateral side, highlighting the significance of CGRP supply through the sensory branch of the genitofemoral nerve for testicular descent.