(+)-Cyclazosin, a selective α_1B-adrenoceptor antagonist: Functional evaluation in rat and rabbit tissues

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• 作者：Gabriella Marucci ; Piero Angeli ; Michela Buccioni ; Ugo Gulini ; Carlo Melchiorre ; Gianni Sagratini ; Rodolfo Testa and Dario Giardinà
• 关键词：α ; ₁-Adrenoceptor subtype ; α ; _1B-Adrenoceptor ; Rabbit aorta ; α ; ₁-Adrenoceptor antagonist ; α ; _1B-Adrenoceptor antagonist ; (+)-Cyclazosin
• 刊名：European Journal of Pharmacology
• 出版年：2005
• 期刊代码：24_00142999
• 类别：neu
• 出版时间：2005
• 卷：522
• 期：1-3
• 页码：100-107
• 文件大小：317 K

摘要

To shed light on the discrepancy between reported binding and functional affinity and selectivity at α_1b/B-adrenoceptors, the antagonist (+)-cyclazosin was reinvestigated in rat and rabbit tissues. It displayed a competitive antagonism at α_1A and α_1D-adrenoceptors of rat prostatic vas deferens and aorta with pA₂ values 7.75 and 7.27, respectively.

In rabbit thoracic aorta (+)-cyclazosin competitively antagonized noradrenaline-induced contractions at α_1B-adrenoceptors with a pA₂ value of 8.85, whereas its affinity at α_1L-adrenoceptors was markedly lower (pA₂ = 6.75 − 7.09).

In conclusion, these data confirmed that (+)-cyclazosin is a selective α_1B-adrenoceptor antagonist also in functional assays, showing 13- and 38-fold selectivity for the α_1B-adrenoceptor over α_1A- and α_1D-subtypes, respectively. Furthermore, (+)-cyclazosin displayed a significant selectivity for α_1B-adrenoceptors relative to the α_1L-subtype.