Effect of moxisylyte on the lower urinary tracts (2). Effect on the urethra in anesthetized dogs]

Effect of moxisylyte on the lower urinary tracts was studied with the urethral pressure profile (UPP) and balloon method in anesthetized female dogs. In the UPP, moxisylyte produced relaxation in both the proximal and distal urethras. The relaxation effects of prazosin and bunazosin on the distal urethra was weaker than on the proximal urethra. In the balloon method, moxisylyte, prazosin, bunazosin and phentolamine caused a decrease in urethral pressure dose-dependently. The ID25 values of moxisylyte, prazosin, bunazosin and phentolamine were 23.4, 0.43, 0.76 and 33.1 micrograms/kg, respectively. In the balloon method, moxisylyte noncompetitively antagonized phenylephrine induced contraction of the urethra at high doses, whereas prazosin, bunazosin, phentolamine and yohimbine competitively antagonized phenylephrine induced contraction of the urethra. These results suggest that moxisylyte relaxes both the proximal and distal urethras due to alpha 1-adrenoceptor antagonistic and direct urethral smooth muscle relaxant actions. Therefore, moxisylyte is useful for the therapeutic treatment of micturitional disorder.