Voiding behavior and chronic pelvic pain in two types of rat nonbacterial prostatitis models: Attenuation of chronic pelvic pain by repeated administration of tadalafil

BACKGROUND: Experimental autoimmune prostatitis (EAP) and prostatitis induced by 17β-estradiol treatment combined with castration (hormone/castration-induced prostatitis; HCP) are the most commonly used rodent models of nonbacterial prostatitis. We studied the effect of the phosphodiesterase 5 inhibitor tadalafil on chronic pelvic pain in two such models in rats. METHODS: EAP was induced by intradermal injection of rat prostate antigen and complete Freund's adjuvant on Days 0 and 28. HCP was induced by castration followed by daily subcutaneous injection of 17β-estradiol for 30 days. On Day 42 after antigen injection in the EAP model and Day 30 after castration in the HCP model, we investigated voiding behavior, pelvic pain (measured by applying von Frey filaments to the lower abdomen), and inflammatory changes, including changes in histopathology and IL-1β, CCL2, and CCL3 mRNA levels. We investigated the effect of repeated administration of tadalafil on chronic pelvic pain in both models. RESULTS: In the EAP model, we observed inflammation in the ventral prostate, while in the HCP model, we observed inflammation in the lateral lobe of the prostate. Neither model showed any change in voiding behavior. As well as in the EAP model, in which chronic pelvic pain was observed, we found for the first time that HCP led to a significant increase in chronic pelvic pain. Repeated treatment with tadalafil attenuated the chronic pelvic pain in both models. CONCLUSIONS: Chronic pelvic pain was induced in both EAP and HCP models. Tadalafil significantly attenuated the chronic pelvic pain in both models.