Denervation and castration effects on the cross-sectional area of pubococcygeus muscle fibers in male rats.

The number of fibers in skeletal muscles changes little through life; however, the cross-sectional area of its fibers is modified as result of denervation and in some muscles by castration. The pubococcygeus muscle (Pcm) participates in micturition and ejaculatory processes and its fibers cross-sectional area is reduced in castrated rats, but denervation effects remained unknown. Here, we used a model in which unilateral denervation of this muscle in gonadally intact and castrated male rats, allowed us to explore the neural and gonadal hormone effects on the cross-sectional area of its fibers. Denervation significantly reduced the mean cross-sectional area values; likewise, the percentage distribution of its fibers. We found that castration had a greater effect than denervation. Castration resulted in a lack of fibers from 2,000 to 3,999 μm(2) , while in denervation it was from 2,500 to 3,999 μm(2) . It was interpreted that the castration effect was due to a lack of the direct gonadal hormone effect on muscle fibers, and to a reduction of the indirect hormonal action in its neuromuscular complex. In denervated Pcm of gonadally intact animals these effects were present; however, in denervated but castrated animals these were absent. Thus, combined surgeries resulted in the lowest mean cross-sectional area values with a restricted fiber distribution from 500 to 1,499 μm(2) . In conclusion, the study in this important muscle showed that cross-sectional area of its fibers depends on neural and direct/indirect gonadal hormone effects.