Regression of the mammary branch of the genitofemoral nerve may be necessary for testicular descent in rats.
OBJECTIVE
Inguinoscrotal testicular descent has been proposed to occur via sensory fibers of the sexually dimorphic genitofemoral nerve, which release a neurotransmitter, calcitonin gene related peptide, to guide the migrating gubernaculum into the scrotum. We hypothesize that androgen mediated regression of the genitofemoral nerve mammary branch is necessary for inguinoscrotal descent in rats. We compared the spatiotemporal development of the genitofemoral nerve in control and antiandrogen treated rats.


METHODS
A total of 29 Sprague-Dawley® rats were collected (animal ethics committee approval A644) in control and antiandrogen treated groups (flutamide, embryonic days 16 to 19, 75 mg/kg body weight/5% ethanol + oil) on embryonic days 17 and 19, and on postnatal day 2. Sagittal sections of the gubernaculum and its surrounding structures were processed for standard histology and immunohistochemistry for androgen receptor, nerves (Tuj1), calcitonin gene related peptide (marker for genitofemoral nerve) and cell nuclei (DAPI).


RESULTS
The inguinal mammary bud, its adjacent androgen receptor and genitofemoral nerve mammary branch (containing calcitonin gene related peptide) persisted from embryonic day 17 to postnatal day 2 in all antiandrogen treated males, yet regressed in all control males by postnatal day 2.


CONCLUSIONS
Antiandrogens resulted in the persistence of the mammary branch and inguinal mammary bud. Persistent genitofemoral nerve mammary branches may arrest or slow down gubernacular migration by releasing calcitonin gene related peptide in the mammary inguinal fat pad, thus reducing the chemotactic gradient to calcitonin gene related peptide from genitofemoral nerve branches in the distal scrotum. We hypothesize that this process may be related to antiandrogen induced cryptorchidism in the rodent.
Department of Pediatrics, University of Melbourne, Parkville, Victoria, Australia.
Shu
S
Su
Pamela J
PJ
Farmer
Ruili
R
Li
Magdy
M
Sourial
Silverton
S
Buraundi
Daniela
D
Bodemer
Bridget R
BR
Southwell
John M
JM
Hutson
D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000502:physiology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013737:Testis / Q000196:embryology* / Q000294:innervation*
D015740:Calcitonin Gene-Related Peptide