Sino-atrial node

Targets and spirals have been observed in the CIMA/CDIMA system [13] and also in dilute flames (i.e. flames close to their lean flammability limits) in situations of enlianced heat loss [33]. In such systems, substantial fiiel is left unbumt. Spiral waves have also been implicated in the onset of cardiac arrhytlnnia [32] the nomial contractive events occurring across the atria in the mannnalian heart are, in some sense, equivalent to a wave pulse initiated from the sino-atrial node, which acts as a pacemaker. If this pulse becomes fragmented, perhaps by passing over a region of heart muscle tissue of lower excitability, then spiral structures (in 3D, these are scroll waves) or re-entrant waves may develop. These have the incorrect... 

Masumiya H, Saitoh T, Tanaka Y, et al. Effects of hirsutine and dihydrocorynantheine on the action potentials of sino-atrial node, atrium and ventricle. Life Sci 1999 65 2333-2341. 

E. A. Accili, G. RedaelU, D. DiFrancesco (1998). Two distinct pathways of mnscarinic current responses in rabbit sino-atrial node myocytes. Pftugers Arch. 437 164. 

Recently, both hirsutine (85) and dihydrocorynantheine (86) were found to be active when the effects of these compounds on the action potentials of sino-atrial node, atrium and ventricle tissues were studied with standard microelectrode techniques [65]. In sino-atrial node preparations, both compounds concentration-dependently increased cycle length, decreased the slope of the pacemaker depolarization, decreased the maximum rate of rise and prolonged action potential duration. Thus, it was for the first time shown that hirsutine and dihydrocorynantheine have direct inhibitory effects on the cardiac pacemaker. In atrial and ventricular preparations, both compounds concentration-dependently decreased the maximum rate of rise and prolonged action potential duration. Although stereochemically different, these two alkaloids exhibited no difference in their effects on various myocardial action potential parameters. Dihydrocorynantheine also displays potent a-adrenoceptor blocking activity, while hirsutine is inactive [66]. Experiments with ion channels indicate that the mechanisms for these two phenomena probably differ. The direct effects of hirsutine and dihydrocorynantheine on the action potential of cardiac muscle through inhibition of multiple ion channels may explain the negative chronotropic and antiarrhythmic activities of these two alkaloids. 

Trautwein W, Osterrieder W, and Noma A (1980) Potassium channels and the muscarinic receptor in the sino-atrial node of the heart in Drug Receptors and their Effectors, ed. N.J.M. Birdsall (New York Macmillan) pp 5-22... 

Gamy, A., Kohl, P., Noble, D. and Hunter, P. J. ID and 2D models of the origin and propagation of cardiac excitation from the sino-atrial node into the right atrium. 

Hagiwara et al. (1988) Contribution of two types of calcium currents to the pacemaker potentials of rabbit sino-atrial node cells. J Physiol 395 233-253... 

Abraham, S., Oz, N., Sahar, R., Kadar, T. (2001). QTc prolongation and cardiac lesions following acute organophosphate poisoning in rats. Proc. West. Pharmacol. Soc. 44 185-6. Accili, E.A., Redaelli, G., DiFrancesco, D. (1996). Activation of the hyperpolarization-activated current (if) in sino-atrial node myocytes of the rabbit by vasoactive intestinal peptide. Pflugers Arch. - Eur. J. Physiol. 431 803-5. 

Cardiac excitation originates in the sino-atrial node and propagates through the atria into the atrial-ventricular node. The impulse then enters the Purkinje conduction system, which delivers the excitatory wave to the ventricles. Ventricular excitation spreads from the endocardium to the epicardium and is coupled to the... 

Ono K, Shibata S, Iijima T. 2000. Properties of the delayed rectifier potassium current in porcine sino-atrial node cells. J. Physiol. 524(Pt. 1) 51—62... 

Noble, D. S.J. Noble. 1984. A model of sino-atrial node electrical activity... 

Yanagihara, K., A. Noma, and H. Irisawa (1980). Reconstruction of sino-atrial node pacemaker potential based on the voltage clamp experiments. Japan. J. Physiol. 30,841-857. 

Sino-atrial node Action potentials Cardiac contraction... 

Matsuura H, Ehara T, Ding WG, Omatsu-Kanbe M, Isono T. Rapidly and slowly activating components of delayed rectifier K(+) current in guinea-pig sino-atrial node pacemaker cells. J Physiol. 2002 540 815-830. 

Soejima M, Noma A. Mode of regulation of the ACh-sensitive K-channel hy the muscarinic receptor in rabbit atrial cells. Pflugers Arch. 1984 400 424-431. DiFrancesco D, Tromba C. Muscarinic control of the hyperpolarization-activated current (if) in rabbit sino-atrial node myocytes. J Physiol. 1988 405 493-510. 

Unlike the L-type cardiac Ca current, the T-current rapidly inactivates and is involved in pacemaker activity in the sino-atrial node and intracellular Ca " -induced Ca release. 

Accili, E.A., Redaelli, G., DiPrancesco, D., 1996. Activation of the hyperpolarization-activated current (Jf) in sino-atrial node myocytes of the rabbit by vasoactive intestinal peptide. Pflugers Arch.—Eur. J. Physiol. 431, 03-805. 

D. Gros, M. Theveniau-Ruissy, M. Bernard, T. Calmels, F. Kober, G. Sohl, K. Willecke, J. Nargeot, H.J. Jongsma, M.E. Mangoni, Connexin 30 is expressed in the mouse sino-atrial node and modulates heart rate, Cardiovasc Res 85 (2010) 45-55. 

---