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在大鼠心脏上同时激动α１肾上腺素受体（α１－ＡＲ）与β－肾上腺素受体的（β－ＡＲ），较单独激动β－ＡＲ时产生的ｃＡＭＰ明显减少，α１Ａ－ＡＲ亚型抑制，而α１Ｂ－ＡＲ亚型增强β－ＡＲ刺激ｃＡＭＰ生成的作用。但α１－ＡＲ及其亚型激动不影响ｆｏｒｓｋｏｌｉｎ引起的ｃＡＭＰ生成，亦不影响β－ＡＲ与［１２５Ｉ］吲哚洛尔的最大结合容量和解离常数。苯福林激动α１－ＡＲ对三磷酸鸟苷使异丙肾上腺素与［１２５Ｉ］吲哚洛尔的竞争抑制曲线右移程度无显著影响。提示α１－ＡＲ及其亚型影响β－ＡＲ心肌正性变力效应的作用发生在腺苷酸环化酶激动之前的环节，但并不影响β－ＡＲ本身及其与Ｇ蛋白的偶联。
The α1-AR and β-adrenergic receptor (β-AR) were significantly increased in the rat heart compared with those in the β-AR alone, and the α1A-AR subtype was inhibited , While α1B-AR subtype enhances the effect of β-AR on cAMP production. However, the activation of α1-AR and its subtypes did not affect the production of cAMP induced by forskolin, nor did it affect the maximal binding capacity and dissociation constant of β-AR to [125I] pindolol. Phenylephrine agonized α1-AR had no significant effect on the extent of right-shift of competitive inhibition of isoproterenol with [125I] pindolol by guanosine triphosphate. These results suggest that the effect of α1-AR and its subtypes on the positive force effect of β-AR myocardium occurs before the activation of adenylate cyclase but does not affect the β-AR itself and its coupling with G protein.