Abstract
Effect of moxisylyte on the lower urinary tracts was studied in comparison with those of prazosin and bunazosin in the isolated rabbit bladder and urethra. Moxisylyte dose-dependently inhibited the urethral contraction induced by phenylephrine. The IC50 value of moxisylyte was 1.01 ×: 10-6 M. Prazosin and bunazosin inhibited the urethral contraction as well as moxisylyte. The IC50 values of prazosin and bunazosin were 2.88 ×: 10-7 M and 1.44 ×: 10-7 M, respectively. Moreover, moxisylyte and bunazosin inhibited the urethral contraction induced by KCI. The IC50 values of moxisylyte and bunazosin were 1.17 ×: 10-5 M and 1. 35 ×: 10-4M, respectively. The KCl/phenylephrine ratios of moxisylyte, bunazosin and prazosin were as follows: 17, 938 and 9201, respectively. Moxisylyte has a relaxant action on the urethra that is probably ascribable to its al-adrenoceptor antagonist and Ca++ antagonist actions. In the isolated bladder, moxisylyte inhibited the bladder contraction induced by KCl, with an IC50 value of 4.46 ×: 10-5 M. However, moxisylyte did not affect the contractile response to acetylcholine. These results suggest that the relaxant effect of moxisylyte on the urethra is due to α1-adrenoceptor antagonist and Ca++ antagonist actions. Therefore, moxisylyte is useful for the therapeutic treatment of micturitional disorder.
