Imidazoline binding sites and receptors related with cardiovascular functions / 中国药理学通报

ABSTRACT

I 2 Imidazoline binding sites have been shown to exist on cardiac myocytes of human beings and rat. Both of I 1 and I 2 imidazoline binding sites have been identified on vascular smooth muscle cells of various species. Vascular I 2 imidazoline binding sites may participate in vascular smooth muscle proliferation. The sympathetic nerves supplying the cardiovascular system are endowed with presynaptic inhibitory imidazoline receptors. Being different from most of the imidazolines, moxonidine does not activate presynaptic imidazoline receptors, but SR141716A, which is considered as a selective antagonist at cannabinoid receptors, antagonizes presynaptic imidazoline receptors. It has been shown that imidazolines exhibit antiarrhythmic action. Agamatine, which is endogenous ligand at imidazoline receptors, not only decreases the rate of pacemaker firing in sinoatrial node of animal, prolongs action potential duration on cardiac myocytes of human beings and animal, but also inhibits afterdepolarizations induced by isoproterenol. On the other hand, imidazolines and guanidines inhibit the cardiovascular K ATP channel in a noncompetitive manner, those effects might interfere with the cardioprotective effects of K ATP channel.