Antagonistic effect of tetrahydroproberberine homologues on alpha 1-adrenoceptor
Lu, Z.Z.; Wei, X.; Jin, G.Z.; Han, Q.D.
Yao Xue Xue Bao 31(9): 652-656
1996
ISSN/ISBN: 0513-4870 PMID: 9863229 Document Number: 463646
The antagonistic effect of tetrahydroproberberine (THP) homologues on alpha-1-adrenoceptor was studied by combination of radioligand binding assays and measurements of vasoconstriction responses. The results showed that l-tetrahydropalmatine (l-THP), l-stepholidine (l-SPD), THPB-18 and tetrahydroberberine (THB) competitively inhibited the 125I-BE2254 specific binding in rat cerebral cortex with pK-I values of 5.54 +- 0.36, 5.56 +- 0.47, 5.75 +- 0.56 and 6.01 +- 0.60, respectively, and the Hill efficiency was not significantly different from unity. They inhibited phenylephrine-induced constrictions with pA-2 values of 5.48 +- 0.58, 5.66 +- 0.54, 5.64 +- 0.34 and 5.45 +- 0.76, respectively, and the slopes of Schild plot were not significantly different from unity. The results indicate that the 4 THP homologues are non-subtype selective competitive antagonists for alpha-1-adrenoceptor with similar affinities.