Lack of feminization of the cremaster nucleus by prenatal flutamide administration in the rat and pig

Purpose: The sexually dimorphic cremaster nucleus contains motoneurons that project via the genitofemoral nerve and theoretically direct androgen dependent testicular descent, The effects of flutamide on descent and masculinization of the cremaster nucleus were studied in the rat and pig. Materials and Methods: Flutamide was given to pregnant rats and pigs on days 16 to 22 and 65 to 113 of gestation, respectively, Tissues were perfused and examined at birth (pigs) or at age 30 days (rats), Spinal cords were removed, sectioned and immunohistochemically stained for serotonin (rats) or substance P (pigs) to demarcate the position of the cremaster nucleus and allow the determination of cremaster motoneuron number. Results: After exposure to flutamide testes were undescended in 6 of 9 rats and 7 of 10 pigs. Cremaster motoneuron number per nucleus were 288 +/- 22 in control versus 250 +/- 27 in flutamide treated rats, and 165 +/- 28 in control versus 148 +/- 24 in flutamide treated pigs. The decrease in motoneuron number by flutamide was significant in both species (p <0.02) but it did not approach the levels in female rats (93 +/- 11) and pigs (57 +/- 12). Cremaster motoneuron number did not correlate with testicular position. Porcine undescended testes were associated with a significant increase in mean gubernacular volume. Conclusions: Unlike other sexually dimorphic spinal cord nuclei masculinization of the cremaster nucleus appears to be largely androgen independent and it does not correlate with ipsilateral testicular descent. These data suggest that androgens do not mediate descent of the testes via the efferent limb of the genitofemoral nerve.