Exogenous calcitonin gene-related peptide causes gubernacular development in neonatal (Tfm) mice with complete androgen resistance.

It has been proposed that testicular descent is controlled indirectly by androgens acting on the central nervous system to mediate migration of the gubernaculum to the scrotum. Accumulating evidence suggests that the genitofemoral nerve may release a newly described neurotransmitter, calcitonin gene-related peptide (CGRP) to stimulate gubernacular motility during migration. This study aimed to determine whether exogenous CGRP could stimulate gubernacular migration in mice with complete androgen resistance (testicular feminization mouse [Tfm]). CGRP was injected into the right groin of neonatal Tfm mice at 2-day intervals until 2 weeks of age, when the length of the processus vaginalis was measured under a dissecting microscope. The processus vaginalis length in normal male littermates was 5.9 +/- 1.8 mm (mean +/- SD) while in the female it was 1.2 +/- 0.9 mm. Exogenous CGRP had no effect on either of these. In Tfm males CGRP caused a significant increase in the length of the processus vaginalis on the injected side (2.3 +/- 0.8 mm) compared with the uninjected side (1.4 +/- 1.0 mm). These results are consistent with the hypothesis that CGRP can replace, at least partially, the effect of androgens on gubernacular migration.