Bilateral orchiectomy deteriorates the structure and function of seminal vesicles in a rat model.

The effects of hormone levels on ejaculation are known. In addition to thyroid hormone levels, testosterone levels are also associated with ejaculation, but no consensus has been reached on this issue. Thus, we investigated the effect of decreased testosterone levels due to bilateral orchiectomy on the chemical stimulation-induced ejaculation phases in rats. Twenty-one male Wistar rats were randomized into the orchiectomy, sham, and control groups, with seven rats in each group. Bilateral orchiectomy was performed. The ejaculation parameters were evaluated 5 days after the sham and bilateral orchiectomy operations and the waiting period in the control group. The seminal vesicle (SV) phasic contraction number and increase in basal pressure amplitude were significantly lower in the orchiectomy group (6.9 ± 3.3 and 0.6 ± 0.3 mmHg) than in the sham and control groups (11.2 ± 1.7 and 1.0 ± 0.4 mmHg, and 14.5 ± 6.6 and 1.1 ± 0.2 mmHg, respectively; p = 0.016 and p = 0.03, respectively). The interval between the SV contractions was significantly longer in the orchiectomy group (166.2 ± 104.3 s) than in the sham and control groups (76.0 ± 15.5 s and 63.1 ± 31.1 s, respectively; p = 0.014 (between groups), orchiectomy vs sham p = 0.040 and orchiectomy vs control p = 0.018). The SV weights of the rats were significantly lower in the orchiectomy group (0.14 ± 0.01 g) than in the sham and control groups (0.37 ± 0.05 g and 0.48 ± 0.03 g respectively; p < 0.0001 (between groups), orchiectomy vs sham p < 0.0001 and orchiectomy vs control p < 0.0001). The groups showed no significant differences in ejaculation time, SV basal pressure, SV maximum amplitude, and bulbospongiosus muscle contraction electromyographic activity. Our results partially clarified the relationship between decreased testosterone levels and ejaculation. Decreased testosterone levels caused statistically significant changes in SV functions and affected the ejaculation emission phase.