Effect of Gonadal Hormones on the Cross‐Sectional Area of Pubococcygeus Muscle Fibers in Male Rat

Abstract

Effects of gonadal hormones on dimorphic striated muscles such as the bulbocavernosus/levator ani complex related to male penile erection have been widely studied. However, the action of these hormones on pelvic nondimorphic muscles is not known. In the present study, the sensitivity of the male rat pubococcygeus muscle (Pcm) to gonadal hormones was studied measuring the cross-sectional area (CSA) of its fibers. For this, two experiments were done: in the first, the effect of castration, and in the second the effect of gonadal hormone administration was analyzed. We found that castration after 6 weeks significantly reduced the average CSA of the fibers of this muscle and that castration after 2 or 6 weeks reduced the percentage of fibers with higher CSAs, but only castration after 6 weeks increased the percentage of fibers with the lowest CSA. In comparison with castrated animals implanted with an empty Silastic capsule, Silastic implants of testosterone propionate or dihydrotestosterone significantly increased the average CSA of Pcm fibers, and the treatment with testosterone propionate, estradiol benzoate, or dihydrotestosterone decreased the percentage of fibers with low CSAs and increased the percentage with larger CSAs. Our results could be considered for therapy in patients with damage of the Pcm, and suffering urinary incontinence or ejaculatory dysfunctions. Anat Rec, 291:586-592, 2008. 2008 Key words: pubococcygeus muscle; dihydrotestosterone; cross-sectional area; estradiol benzoate; testosterone propionate Effects of gonadal hormones on dimorphic striated muscles related to male reproductive physiology have been studied widely, particularly the bulbocavernosus/ levator ani complex implicated in mechanisms of penile erection. It has been shown that androgens affect muscle weight (Tucek et al

Denervation and Castration Effects on the Cross‐Sectional Area of Pubococcygeus Muscle Fibers in Male Rats

“…In male rats, this muscle is not part of the levator ani complex (Yuan et al, 2003); however, its participation in micturition and ejaculation is highlighted through behavioral studies (Manzo et al, 2000) and by electrical stimulation of its nerve (Manzo et al, 1997). Furthermore, by analyzing the cross-sectional area of its fibers, we have shown that this muscle is sensitive to gonadal hormones (Alvarado et al, 2008), but we still do not know whether this effect is due to a direct action of these hormones on its fibers and/or through the neuromuscular complex, in which hormonal changes affect soma size, synaptic efficiency, and neuromuscular junction size of muscles such as the bulbocavernosus and levator ani (Breedlove and Arnold, 1981;Balice-Gordon et al, 1990;Tanaka and Arnold, 1993).…”

“…Muscles were then immersed in Helly's fixer for 24 hr, washed with distilled water for 2 hr, and dehydrated in alcohols. Using a similar procedure previously described (Alvarado et al, 2008), 20 transverse serial sections (7 lm each) were obtained from a piece of muscle (4 mm in length) close to the origin, and stained with hematoxylin and eosin.…”

“…The section at 310 magnification was then divided using a grid with 12 3 8 compartments (100 lm 3 100 lm each compartment). From this grid, five sample fields were randomly selected, and from each one of these sample fields, five fibers (similar to those represented in Fig.1 from Alvarado et al, 2008) were randomly selected and a blinded second observer carried out the measurements. A total of 25 fibers per muscle, that is, 150 fibers per group were analyzed using a light microscope (Olympus BH-2) and software for morphology measurement (Sigma ScanPro 4; Aspire Software International, USA).…”

Electromyography of Pelvic Floor Muscles in Rats

“…The discharge stopped when the tail was placed in the midline. Since muscle spindles have been described in the pubococcygeus muscle (Alvarado et al 2008), the activity related to tail contralateral movement may be a reflex response with muscle spindles as afferents. In a prone position, the coccygeus muscle and most of the pubococcygeus recording sites did demonstrate activity during micturition.…”

“…Their morphometric characteristics are modulated by gonadal www.intechopen.com steroid hormones, as indicated by soma size and dendrite length and arborization reduction after ovariectomy and recovery after steroid treatment (Cuevas et al 2006). In males it has been shown that the muscle fibers are also sensitive to gonadal steroids since castration reduces the cross-sectional area of the pubococcygeus muscle (Alvarado et al 2008). Afferents involved in induction of reflex activity of pelvic floor muscles travel through the pudendal and pelvic nerves (Pacheco et al 1989).…”