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[Effects of tetrahydroberberine on peripheral vascular dopamine DA1 and DA2 receptor subtypes]
1Department of Physiology, Shanxi Medical University, Taiyuan 030001 Shanxi, China.
Objective:
To study the effect of tetrahydroberberine (THB) on the peripheral vascular dopamine DA1 and DA2 receptors.
Method:
Using isolated vascular rings method.
Result:
THB(0.1-10 mumol.L-1) shifted the dose-response curves to the right in a nonparallel fashion and decreased the maximal response (Emax) of both the fenoldopam(FODA, a selective DA1 agonist)-induced and the propyl-butyl-dopamine(PBDA, a selective DA2 agonist)-induced vasorelaxation, showing a non-competitive antagonistic action. The pD'2 values of THB for FODA in the renal, pulmonary and mesenteric arteries were 5.29, 5.37 and 5.46, respectively, while for PBDA in the mesenteric and femoral arteries were 5.53 and 5.48, respectively. The potencies of this antagonistic action were weaker than those of SCH23390, a selective DA1 antagonist, domperidone, a selective DA2 antagonist and l-SPD, a mixed DA1/DA2 antagonist, domperidone, a selective DA2 antagonist and l-SPD, a mixed DA1/DA2 antagonist.
Conclusion:
THB is a mixed peripheral DA, and DA2 receptor antagonist similar to l-SPD.