HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bywater, R A Articles by O'Shea, J E Search for Related Content PubMed PubMed Citation Articles by Bywater, R A Articles by O'Shea, J E

Department of Zoology, University of Melbourne, Parkville, Victoria, Australia.

1. The effects of vagal stimulation and applied acetylcholine were compared on the isolated sinus venosus preparation of the toad, Bufo marinus. 2. The effects of applied acetylcholine and of low-frequency, or short bursts of high-frequency vagal stimulation were abolished by hyoscine. 3. When intracellular recordings were made from muscle cells of the sinus venosus, it was found that applied acetylcholine caused bradycardia and a cessation of the heart beat which was associated with membrane hyperpolarization and a reduction in the duration of the action potentials. Much of the effect of acetylcholine can be attributed to it causing an increase in potassium conductance, gK. 4. When slowing was produced by low-frequency vagal stimulation, only a small increase in maximum diastolic potential was detected. During vagal arrest the membrane potential settled to a potential positive of the control maximum diastolic potential. 5. In the presence of barium, much of the bradycardia associated with vagal stimulation persisted. Although the bradycardia produced by added acetylcholine also persisted in the presence of barium, the effects of acetylcholine that could be attributed to an increase in gK were abolished. 6. Addition of caesium ions produced bradycardia with membrane potential changes similar to those seen during vagal stimulation. 7. The results are discussed in relation to the idea that neuronally released acetylcholine reduces inward current flow during diastole. In contrast applied acetylcholine as well as reducing inward current flow during diastole also increases outward current flow by increasing gK.

This article has been cited by other articles:

				C. P. Bolter and D. J. English The effects of tertiapin-Q on responses of the sinoatrial pacemaker of the guinea-pig heart to vagal nerve stimulation and muscarinic agonists Exp Physiol, January 1, 2008; 93(1): 53 - 63. [Abstract] [Full Text] [PDF]

				W. J. Zang, L. N. Chen, X. J. Yu, P. Fang, J. Lu, and Q. Sun Comparison of effects of acetylcholine on electromechanical characteristics in guinea-pig atrium and ventricle Exp Physiol, January 1, 2005; 90(1): 123 - 130. [Abstract] [Full Text] [PDF]

				J. K. Choate and R. Feldman Neuronal control of heart rate in isolated mouse atria Am J Physiol Heart Circ Physiol, August 7, 2003; 285(3): H1340 - H1346. [Abstract] [Full Text] [PDF]

				M.R. Boyett, H. Honjo, and I. Kodama The sinoatrial node, a heterogeneous pacemaker structure Cardiovasc Res, September 1, 2000; 47(4): 658 - 687. [Abstract] [Full Text] [PDF]

				E. J. Dickens, F. R. Edwards, and G. D. S. Hirst Vagal inhibition in the antral region of guinea pig stomach Am J Physiol Gastrointest Liver Physiol, August 1, 2000; 279(2): G388 - G399. [Abstract] [Full Text] [PDF]