Estrogen receptor subtypes and afferent signaling in the bladder

The influence of estrogen on bladder function has been the subject of several experimental and clinical studies. In addition to the well-known estrogen receptor (ER)alpha, recently the ER subtype ERbeta was discovered. We investigated potential changes in bladder function in mice lacking either 1 or both receptor subtypes compared with WT mice.

Female mice lacking genes for ERalpha (ERKO), ERbeta (BERKO) or both and their WT littermates were used for the study. Continuous cystometry in awake animals was performed before and after intravesical administration of capsaicin. In addition, in vitro responses to electrical field stimulation before and after incubation with scopolamine and alpha,beta-methylene adenosine triphosphate, and to carbachol were investigated.

Control cystometry revealed no significant difference in urodynamic parameters among all strains. After capsaicin instillation the micturition interval and volume decreased, and micturition pressure increased in WT, ERbeta and 2 gene mice, while no changes were seen in ERKO mice. In vitro contractility was similar in all groups. Incubation with scopolamine and alpha,beta-methylene adenosine triphosphate led to significant decreases in the response to electrical field stimulation. There was no difference in the response to carbachol among the groups.

The lack of ERalpha and/or ERbeta had little effect on in vitro contractility or on continuous cystometry in awake animals. The lack of response to capsaicin instillation in ERKO suggests that ER subtypes are important for vanilloid receptor function and mechano-afferent signaling.