Introduction Although premature ejaculation (PE) is the most common sexual dysfunction in young men, its true pathophysiology has not yet been clearly elucidated. Aim To investigate the quantitative changes that occurred in an ejaculation model induced by para-chloroamphetamine (PCA) after botulinum-A toxin injection into the bulbospongiosus (BS) muscle in rats. Methods A total of 21 male rats weighing 300 to 350 grams were used in the study. The animals were divided into 3 groups: control, 1 unit of botulinum-A toxin injected, and 5 units of botulinum-A toxin injected. The botulinum-A toxin was percutaneously injected into the BS muscle, and the experiment was carried out 96 hours (5 days) after the injection. Main Outcome Measure The seminal vesicle (SV) was cannulated, and the BS muscle was dissected and connected to an amplifier (Biopac; Goleta, CA) to record the pressure and electromyography measurement. The ejaculation parameters were obtained after the PCA injection. Results The ejaculation latency time of the group receiving 5 units of botulinum-A toxin was statistically significantly longer (1092 ± 657 seconds) compared to the control group (298 ± 81 seconds) and the group receiving 1 unit of botulinum-A toxin (439 ± 100 seconds) (P = .003). Furthermore, the BS EMG area under the curve values for the group receiving 5 units of botulinum-A toxin were significantly lower (7.4 ± 1.2 V/s × 10–4) than those of the control group (13.6 ± 4.0 V/s × 10–4) and the group receiving 1 unit of botulinum-A toxin (13.6 ± 5.0 V/s × 10–4) (P = .009). No statistically significant difference was found between the groups in terms of the basal SV pressure, number of SV phasic contractions, maximum amplitude of the SV phasic contraction, and intervals between the SV phasic contractions and the BS muscle contractions. Clinical Implications Botulinum-A toxin injection is a potential treatment option for PE and should be further investigated by future clinical studies. Strengths and Limitations Ease of administration and prolonged duration of botulinum-A toxin are advantages of the existing treatment options. The risk of anejaculation due to the dosage should be kept in mind. Conclusions Injection of botulinum-A toxin into the BS muscle in rats significantly delayed the ejaculation latency time and affected the expulsion phase.

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