RESUMO
Aim To study effects of intraduodenal administration of S-doxazosin, R-doxazosin and rac-doxazosin on the carotid blood pressure and urinary bladder function in anesthetized rats. Methods The various parameters of carotid blood pressure, heart rate, vesical micturition pressure, intercontraction interval in anesthetized rats were recorded with an ADInstruments PowerLab/8s data recording and analysis system, and the vesical micturition volume was measured simultaneously. Results S-Doxazosin, R-doxazosin and rac-doxazosin administered intraduodenally decreased the systolic blood pressure, diastolic blood pressure and mean arterial blood pressure significantly in anesthetized rats in a dose-dependent manner. The inhibition of mean arterial pressure by S-doxazosin, R-doxazosin and rac-doxazosin at 1.0 mg?kg-1 was 23.5%?4.6%, 38.5%?8.9% and 42.6%?7.5%, respectively. The ED30 values of decreasing mean arterial blood pressure by S-doxazosin, R-doxazosin and rac-doxazosin were (2.0?0.8),(0.6?0.7) and (0.6?0.5) mg?kg-1,respectively. S-Doxazosin had a weaker inhibitory effect on the carotid blood pressure compared with R-doxazosin and rac-doxazosin, but no significantly different effect was observed between R-doxazosin and rac-doxazosin on the carotid blood pressure. rac-Doxazosin produced a significant inhibition on the heart rate at the dosage from 0.1 mg?kg-1 to 3.0 mg?kg-1 in a dose-dependent manner, but S-doxazosin and R-doxazosin reduced the heart rate only at 3.0 mg?kg-1. S-Doxazosin, R-doxazosin and rac-doxazosin administered intraduodenally decreased the vesical micturition pressure dose-dependently in anesthetized rats. The maximal inhibition of vesical micturition pressure by S-doxazosin, R-doxazosin and rac-doxazosin was 13.4%?5.7%, 14.5%?11.0% and 10.9%?7.6%, and their inhibitory potency on the vesical micturition pressure was not significantly different each other. R-Doxazosin, however, decreased the intercontraction interval and vesical micturition volume significantly compared with S-doxazosin, but S-doxazosin and rac-doxazosin did not significantly affect the intercontraction interval and vesical micturition volume. Conclusion In comparison with R-doxazosin and rac-doxazosin, S-doxazosin administered intraduodenally remains the beneficial action on vesical micturition pressure and relieves the adverse effects on blood pressure, heart rate and intercontraction interval in anesthetized rats.