Mechanisms underlying the contractile responses to doxazosin enantiomers in the rat isolated atrium / 中国药理学通报

ABSTRACT

Aim To study the mechanisms of inotropic responses to doxazosin enantiomers in the isolated rat atrium.Methods We analyzed the positive inotropic response to (-)doxazosin and the negative inotropic response to (+)doxazosin in the left atrium of rat u-sing receptor-pharmacological technique.Results In the preparation treated with verapamil,the positive in-otropic responses to 3 μmol·L-1 (-)doxazosin were significantly inhibited from the control level (245.7 1 ± 44.29)mg to (172.50 ±43.34)mg,(P<0.05).In the preparation treated with methylene blue,the posi-tive inotropic responses to 3 μmol·L-1 (-)doxazosin were significantly potentiated from the control level (245.7 1 ±44.29 )mg to (303.33 ±45 .90 )mg,(P<0.05 ).In the preparation treated with H-89 ,the positive inotropic responses to 3,10 and 30 μmol · L-1 (-)doxazosin were (338.57 ±96.86 ) mg, (471.43 ±107.61)mg and (520.00 ±103.44)mg, which were significantly (P<0.05 ~0.01)larger than the control levels of (245.71 ±44.29)mg,(314.29 ±90.34)mg and (357.14 ±68.49 )mg.Treatment with phenoxybenzamine,atropine,propranolol or indo-methacin did not significantly affect the responses to doxazosin enantiomers.Conclusion The positive ino-tropic responses to (-)doxazosin in the isolated left a-trium of rat are partially involved in L-type Ca2+chan-nels and intracellular cGMP level.However,α-adre-noceptors,muscarinic receptors,β-adrenoceptors and cyclooxygenases are not related to the responses to doxazosin enantiomers.