| Title | Intracellular electrophysiology: direct acute effects of ethanol on automatic activity of isolated rabbit heart sinoatrial node and on internodal pathways | |
| Authors | D.I. Chaniotis1, A. Poyatzi1, M. Lymberi1 and P.A. Molyvdas2
1. Department of Experimental Physiology, University of Athens, Medical School, Athens, Greece 2. Department of Physiology, Faculty of Medicine, University of Thessaly, Larissa, Greece |
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| Citation | Chaniotis, D.I., Poyatzi, A., Lymberi, M., Molyvdas, P.A.: Intracellular electrophysiology: direct acute effects of ethanol on automatic activity of isolated rabbit heart sinoatrial node and on internodal pathways, Epitheorese Klin. Farmakol. Farmakokinet. 16(2): 163-168 (2002) | |
| Publication Date | Received for publication: 15 January 2002
Accepted for publication: 30 March 2002 |
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| Full Text Language | English | |
| Order – Buy | Ηλεκτρονική Μορφή: pdf (10 €) – Digital Type: pdf (10 €)
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| Keywords | Intracellular electrophysiology, ethanol, automatic activity, action potentials, sinoatrial node, internodal pathways, heart pacemaker cells, isoproterenol. | |
| Other Terms | review article | |
| Summary | We investigated the acute effects of increasing ethanol concentrations on membrane action potentials in different regions of rabbit sinoatrial node (SAN) and specialized conduction fibers of the internodal pathways (IP). The preparations were superfused in an organ bath with oxygenated (95%O2 – 5%CO2) Tyrode solution at a constant temperature of 36.5±0.5 °C and a pH 7.2-7.3. The eiectrophysiological activities were recorded by intracellular microelectrodes filled with 3M KCl (resistance 20-30 MΩ). The traces were displayed on a storage oscilloscope and the action potential (AP) parameters, beating frequency (BF), amplitude (APA), maximum diastolic potential (MDP), action potential duration at 50% repolarisation (APD50), and the maximum upstroke velocity (+Vmax), were measured. Increasing ethanol concentrations induced statistically significant modification on the eiectrophysiological parameters. The effects of ethanol were biphasic and dose-dependent on the automatic beating frequency. Specifically, low ethanol concentrations increased the beating frequency and higher ethanol concentrations than 1.7x103M incentral and transitional SAN regions and 34×10–3M in peripheral SAN regions and IP significantly dereased the BF, APA, +Vmax, MDP. Automatic activity was completely blocked at 17×10-3M ethanol concentrations in central pacemaker cells and 51×10-3M in other types SAN and IP cells. The actions of ethanol on the BF was estimated by the dose-response cubic curve regression model. The depressant effects of ethanol were reversed when isoproterenol (ISO) was added in the superfusate or after washout In the beginning phase of washout the automatic activity was accelerated transient and restored to the control rate. Our results suggest that ethanol modifies the spontaneous activity of pacemaker cells in biphasic way. Physical interaction of ethanol with cell membranes may be involved. In addition, a direct block of slow calcium channels is more possible for the effects of ethanol in higher concentrations. | |
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