枳实及其有效成分N-甲基酪胺对心血管受体作用的研究

用恒速灌流泵灌流狗肾、脑及下肢血管,记录血管阻力。动脉或静脉注射枳实或其有效成分N-甲基酪胺,均明显增加肾、脑的血管阻力,此作用可被酚妥拉明所阻滞,提示系通过兴奋血管α受体产生的。N-甲基酪胺对股动脉血管阻力呈先降低后增高的双相反应,其升高阻力的作用是兴奋α受体所致,而其降低下肢血管阻力的作用可能是兴奋骨骼肌血管β₂受体的表现。在恒速灌流使肾血流量已固定的条件下,枳实和N-甲基酪胺在升高血压与肾血管阻力时,仍有短时间的利尿作用,说明此作用与肾血流量的变化无关。N-甲基酪胺能加强离体和在体心脏收缩力,β-受体阻滞剂心得舒能拮抗此作用。利血平化动物实验结果及升压快速耐受性形成,以及减少心肌去甲肾上腺素含量而不影响多巴胺含量等事实表明:N-甲基酪胺与酪胺相似,通过释放去甲肾上腺素兴奋心血管的α和β受体产生效应。

THE EFFECTS OF CITRUS AURANTIUM AND ITS ACTIVE INGREDIENT N-METHYLTYRAMINE ON THE CARDIOVACULAR RECEPTORS

The effects of Citrus aurantium L(Ⅰ) and one of its active ingredients N-methyl-tyramine (Ⅱ) on vascular resistance were studied with roller pump in anethetized dogs. Their actions on receptor were analysed by antagonists. Intra-arterial and intra-venous injection of Ⅰ and Ⅱ increased the renal and cerebral vascular resistance signi-ficantly, which could be antagonized by phentolamine. This suggests that α-receptor sti-mulation is involved. Ⅱ exerted a biphasic effect on femoral artery resistance. This is explained on the differences of distribution in a and β-adrenoceptors.Under constant renal infusion, the transient diuretic action observed after injection of Ⅰ or Ⅱ is independent of the change of renal blood flow.Receptor action of the positive inotropic effect of Ⅱ in guinea pig's auricle strip in vitro, and rabbit heart in situ was attributed mainly to the stimulation of β-adren-ergic receptor.In reserpinized rats and dogs the hypertensive effects of Ⅱ were significantly dee-reased. Pressor tachyphylaxis of Ⅱ similar to tyramine was observed in rats. Assay of adrenergic mediator content in rat myocardium showed significant decrease in nor-epinephrine content after repeated injections of Ⅱ and tyrarnine, while dopamine remained unchanged. It was concluded that the cardiovascular effects of Ⅱ similar to tyramine are resulted from liberation of intrinsic adrenergic mediator, while Ⅰ contains synephrine as well, which shares a direct agonist action on α-receptors.