Osnes J B, Christiansen H B, Horgmo G I, Schiander I G, Skomedal T
Department of Pharmacology, Univ. of Oslo, Norway.
Biomed Biochim Acta. 1987;46(8-9):S417-20.
The alpha- and beta-adrenoceptor mediated inotropic effects of noradrenaline were determined in rat heart papillary muscle. The pure alpha-adrenergic inotropic effect, obtained in the presence of the beta-blocker timolol, was about half the pure beta-adrenergic inotropic effect, obtained in the presence of the alpha-blocker prazosin. The maximal inotropic effect of noradrenaline in the absence of blockers was, however, of the same magnitude as the pure beta-adrenergic effect. The alpha- and beta-adrenergic components of the inotropic response to noradrenaline were determined as those reversed by prazosin and timolol, respectively. They were smaller than the pure effects evoked separately. When beta-stimulation by noradrenaline was attenuated by carbachol, the alpha-adrenergic inotropic component was increased. Thus the alpha-effect is increased when the beta-adrenergic effect is antagonized. The alpha-adrenergic inotropic component of noradrenaline seems to play a variable role depending upon the degree of concomitant beta-receptor stimulation in the heart.
在大鼠心脏乳头肌中测定了去甲肾上腺素由α和β肾上腺素能受体介导的变力作用。在β受体阻滞剂噻吗洛尔存在的情况下获得的纯α肾上腺素能变力作用，约为在α受体阻滞剂哌唑嗪存在的情况下获得的纯β肾上腺素能变力作用的一半。然而，在没有阻滞剂的情况下，去甲肾上腺素的最大变力作用与纯β肾上腺素能作用的大小相同。对去甲肾上腺素变力反应的α和β肾上腺素能成分分别被确定为可被哌唑嗪和噻吗洛尔逆转的成分。它们比分别单独诱发的纯效应要小。当卡巴胆碱减弱去甲肾上腺素的β刺激时，α肾上腺素能变力成分增加。因此，当β肾上腺素能效应被拮抗时，α效应会增加。去甲肾上腺素的α肾上腺素能变力成分似乎根据心脏中伴随的β受体刺激程度发挥不同的作用。
