The action of BTHP on a-adrenoceptor was studied in anococcy-geus muscles, vas deferens and cell membrane of cerebral cortex of rats and aortic strips, saphenous vein of rabbit. BTHP produced parallel shifts to the right of dose-response curves for phenylephrine in rat anococcygeus muscle and rabbit aortic strips without change in the maximal responses. Their pA2 values were 5.8 and 5.86 respectively. BTHP was also a competitive antagonist for presynaptic and postsynaptic ?2-adrenoceptors on prostatic portion of rat vas deferens( pA2 against clonidine=5.2 ) and on rabbit saphenous vein ( pA2 against B-HT920=5.3 ) . BTHP decreased in dose-dependent manner 〔8H〕 prazosin and 〔3H〕 clonidine specific binding to ?1- and ?2- adrenoceptors on cell membrane of cerebral cortex in rats with IC50 of4 and 9.5 ?mol/L and with Ki ( apparent dissociation constant ) of 3.5 and 8.1?mol/L respectively, suggeating that BTHP has affinity for both ?1 and ?2- adrenoceptors of rat cerebrance.

Objective To assess the therapeutic efficiency of short anterior urethral stricture treated with endourethral surgery combined with iridium 192 radiation therapy in order to decrease the recurrence rate after endourethral surgery. Methods A total of 286 patients with anterior urethral stricture (stricture length ranging from 0.5 to 2.5cm, averaging at 1.6cm) were divided randomly into two groups after internal urethrotomy and cicatrix electrotomy. The radiation group of 173 patients was treated as soon as possible with iridium 192 radiation therapy on the stricture sections while the control group of 113 patients was not. The recurrence rate was compared between the two groups during one year's follow-up. Results Among all the 286 successful operations, stricture recurred in 19 patients of the radiation group (recurrence rate of 10.98%) and in 62 ones of the control group (recurrence rate of 54.86%), with a significant difference (P=0.003). Conclusion It is an effective way to prevent recurrence by treating patients as early as possible with iridium 192 radiation on the stricture sections after endourethral operation on anterior urethral stricture.