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Abstract
Clonidine produced an inhibition of the electrical stimulationevoked contraction of the prostatic portion of the rat vas deferens. Berberine and yohimbine suppressed markedly the effect of clonidine. However, washing away the clonidine by Krebs’ solution produced a slow recovery of the responses.
Both berberine and yohimbine shifted clonidine cumulative dose-response curve rightward parallelly without decreasing the maximal response in rat vas deferens. The pA2 values of berberine and yohimbine were 5.3 and 7.8 respectively.
The contractile response to phenylephrine was competitively inhibited by berberine and prazosin in anococcygeus muscle from the same rat. The pA2 values of berberine and prazosin were 6.4 and 8.5 respectively.
The results indicate that berberine possesses competitive α1 and α2 blocking action like prazosin and yohimbine, and its selective ratio (α1/α2) was 8. As compared with these 2 drugs, the selectivity of berberine was much poorer. pD2 values were 8.8 for clonidine and 5.6 for phenylephrine.
Keywords
berberine
/
prazosin
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yohimbine
/
phenylephrine
/
clonidine
/
anococcygeus muscle
/
vas deferens
/
drug dose-response relationship
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Yao Wei-xing, Fang Da-chao, Cheng Bin, Jiang Ming-xing.
Blocking action of berberine on α2- and α1-adrenoceptors in rat vas deferens and anococcygeus muscle.
Current Medical Science, 1987, 7(4): 233-238 DOI:10.1007/BF02888449
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