Differential effects of Bay k 8644, a presumed calcium channel activator, on sinoatrial nodal and ventricular automaticity of the dog heart
- 29 Downloads
- 11 Citations
Summary
Bay k 8644 is suggested to increase calcium influx through the voltage-dependent calcium channel. In isolated, blood-perfused sinoatrial node preparations of the dog, Bay k 8644 injected intra-arterially increased sinus rate as isoprenaline did. In isolated, blood-perfused papillary muscle preparations of the dog isoprenaline injected intra-arterially increased both the force of contraction of the papillary muscle and its spontaneous beating rate. In these preparations, however, Bay k 8644 failed to increase the beating rate, although it increased the force of contraction. These results are consistent with the concept that the slow inward current plays a role in sinoatrial nodal automaticity but not in automaticity of Purkinje fibres which was reflected as ventricular automaticity of the papillary muscle preparations used here.
Key words
Bay k 8644 Isoprenaline Calcium channel activator Sinoatrial nodal automaticity Ventricular automaticityPreview
Unable to display preview. Download preview PDF.
References
- DiFrancesco D (1981) A new interpretation of the pace-marker current in calf Purkinje fibres. J Physiol (Lond) 314:359–376Google Scholar
- Endoh M, Hashimoto K (1970) Pharmacological evidence of autonomic nerve activities in canine papillary muscle. Am J Physiol 218:1459–1463Google Scholar
- Endoh M, Yanagisawa T, Taira N (1978) Effects of calcium-antagonistic coronary vasodilator, nifedipine and verapamil, on ventricular automaticity of the dog. Naunyn-Schmiedeberg's Arch Pharmacol 302:235–238Google Scholar
- Fleckenstein A (1983) Calcium antagonism in heart and smooth muscle. John Wiley Sons, New York Chichester Brisbane Toronto SingaporeGoogle Scholar
- Hauswirth O, Nobel D, Tsien RW (1968) Adrenaline: Mechanism of action on the pacemaker potential in cardiac Purkinje fibers. Science 162:916–917Google Scholar
- Kubota K, Hashimoto K (1973) Selective stimulation of the parasympathetic preganglionic nerve fibres in the excised and blood-perfused SA node preparation of the dog. Naunyn-Schmiedeberg's Arch Pharmacol 278:135–150Google Scholar
- Noble D (1975) The initiation of the heart beat. Clarendon Press, OxfordGoogle Scholar
- Noma A, Kotake H, Irisawa H (1980) Slow inward current and its role mediating the chronotropic effect of epinephrine in the rabbit sinoatrial node. Pflügers Arch 388:1–9Google Scholar
- Reuter H (1974) Localization of beta adrenergic receptors, and effects of noradrenaline and cyclic nucleotides on action potentials, ionic currents and tension in mammalian cardic muscle. J Physiol (Lond) 242:429–451Google Scholar
- Satoh K, Yanagisawa T, Taira N (1980) Mechanisms underlying the cardiovascular action of a new dihydropyridine vasodilator, YC-93. Clin Exp Pharmacol Physiol 7:249–262Google Scholar
- Schramm M, Thomas G, Towart R, Franckowiak G (1983a) Novel dihydropyridines with positive inotropic action through activation of Ca2+ channels. Nature 303:535–537Google Scholar
- Schramm M, Thomas G, Towart R, Franckowiak G (1983b) Activation of calcium channels by novel 1,4-dihydropyridines. A new mechanism for positive inotropics or smooth muscle stimulants. Arzneim-Forsch 33:1268–1272Google Scholar
- Taira N (1979) Effects of diltiazem and other calcium-antagonists on cardiac functions and coronary blood flow as assessed in blood-perfused dog-heart preparations. In: Bing RJ (ed) New drug therapy with a calcium antagonist. Diltiazem Hakone Symposium '78. Excerpta Medica, Amsterdam Princeton, pp 91–103Google Scholar
- Taira N, Kawada M, Satoh K (1983) Cardiac versus coronary vasodilator actions of KB-944, a new calcium antagonist, assessed in isolated, blood-perfused heart preparations of dogs. J Cardiovasc Pharmacol 5:349–356Google Scholar
- Tsien RW (1974) Effect of epinephrine on the pacemaker potassium current of cardiac Purkinje fibers. J Gen Physiol 64:293–319Google Scholar