The differences in the adrenergic receptors of proximal urethra between sexes

OBJECTIVES: The bladder and urethra work as a physiologically functional unit to facilitate continence in the storage and voiding phase. Sex differences have been found in the urethral contraction in response to α-adrenergic receptor activation. This study aimed to investigate the role of adrenergic receptors in the proximal urethra of male and female mice. MATERIALS AND METHODS: Urinary bladder and proximal urethral smooth muscle (USM) samples from male and female C57BL/6 mice were isolated and mounted in an organ bath. RESULTS: Acetylcholine-induced contraction of the urinary bladder was compared in male and female mice. Phenylephrine and norepinephrine (NE) induced little contraction at a lower concentration, but a relaxing phase of female proximal USM was observed at a higher concentration. This contraction profile was inhibited by N(G)-nitro-L-arginine, lidocaine, and capsaicin. In addition, the NE-induced contraction was greater in the incubation of propranolol than that of L-NNA or lidocaine. These results suggested that the β-adrenoceptor may be the dominant receptor of female proximal USM, and the activity of calcitonin gene-related peptide sensory nerves and nitrergic nerves may pose an anti-contraction effect on the proximal urethra in female mice. CONCLUSION: β-adrenoceptor may be the dominant receptor of female proximal USM. The use of β-adrenergic receptor blocker agents might have the potential for the treatment of female voiding dysfunction.