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There exist α_(1A), α_(1B), α_(1D), β_1, and β_2 subtypes ofadrenoceptors (AR) in rat hearts. Its physiological significancehas not been clear. We investigated the crosstalks between thosecoexisted subtypes in the rat heart and HEK 293 cells. Ourresults indicated: (1) In electric driven isolated rat left atria,either α_(1A~-) or α_(1B~(-AR)) per se induced positive inotropic response(PIR). But when they were artivated together with β-AR, theα_(1A)-AR inihibited, while the α_(1B)-AR potentiated the β-AR mediatedPIR and cAMP accumulation. The α_(1D)-AR did not show aboveeffects. When all the subtypes of α_1-AR were acticated with β-AR, the α_(1A)-AR played a dominated effect. Activation of α_1-ARshowed no effect on the foskolin-induced cAMP accumulation. Italso did not change the binding characteristiics of β-AR. Those
There exist α 1A, α 1B, α 1D, β 1, and β 2 subtypes of adrenoceptors (AR) in rat hearts. 293 cells. Ourresults indicate: (1) In electric driven isolated rat left atria, either α_ (1A ~ -) or α_ (1B ~ (-AR)) per se induced positive inotropic response (PIR). But when they were artivated together (1) -AR didihibited, while the α - (1B) -AR potentiated the β-AR mediated PIR and cAMP accumulation. The α_ (1D) -AR did not show above effects. When all the subtypes of α_1- AR were acticated with β-AR, the α_ (1A) -AR played a dominated effect. Activation of α_1-ARshowed no effect on the foskolin-induced cAMP accumulation. Those did not change the binding characteristiics of β-AR.