THE EFFECTS OF AUTONOMIC AGONISTS ON THE FEMALE RABBITS URETHRA

In vitro Isovolumetric and Isometric Study

Abstract

To investigate the characteristics of adrenoceptors of the proximal urethra in female rabbits, we performed the in vitro isovolumetric urethral pressure study and isometric study with three parts of muscle strips of the proximal urethra (whole layers, inner layers and outer layers).
Both alpha-1 and alpha-2 agonist caused dose dependent response in in vitro .isovolumetric pressure study as well as in vivo study. However, the response of alpha-2 agonist in in vitro was small in magnitude compared to in vivo study, suggesting the influence of permeability of drugs from serosa to mucosa in in vitro whole urethra study. The response of the strips of inner layers to alpha-1 agonist is almost the same as that of outer layers and whole layers, while the response of inner layers to alpha-2 agonist is almost twice as that of other layers. These findings are suggestive of predominance of alpha-2 adrenoceptors mediating contractions in the inner layers of the proximal urethra in female rabbits. Alpha-2 adrenoceptors which probably are distributed in mucosal and submucosal layers may have an important role in the mechanism of urinary continence in female rabbits.