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KMID : 0377519830080010039
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Chung-Ang Journal of Medicine
1983 Volume.8 No. 1 p.39 ~ p.45
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A Study of Electrical Properties in the Sinus Venosus of the Frog
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Ahn Byung-Gyu
Uhm Dae-Yong
Rhee Sang-Don
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Abstract
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The frog sinus venosus were studied with conventional glass microelectrode technique in order to elucidate the underlying mechanism of spontaneous pacemaker activity. The analyses were focussed on the ionic nature of pacemaker current by changing the concentrations of extracellular K^+ and/Na^+, or by using blockers of K- and Ca-current and chronotropic transmitters. 1. The action potential sinus venosus has some characteristic feature of maximal diastolic potential ranged from -65 to -75mV, resting potential from -45 to -50 mV and overshoot voltage about +20mV, respectively. Duration of the action potential taken from rapid upstroke to maximal diastolic potential was about 600 msec. Usual discharge rate was 30~35/min at room temperature(18~20℃). 2. In Ringer solution containing 50% Na(substituted by equimolar Tris) reduction of extracellular sodium concentrations diminished the amplitude and frequency of the action potential. And 0 and 11 mm Na hyperpolarize the restal membrane potential greatly. It suggest the resting Na Conductance is significantly high in sinus venosus. 3. Caesium(10mM), K-current blocker decreased pacemaker depolarization. Manganese(2mM) known to be Ca-current antagonist, blocked spontaneous activity completely. 4. Adrenaline and acetylcholine showed positive and negative chronotropic effect. It is concluded that K-, Na- and Ca-current components are involved in the genesis of spontaneous activity of the frog sinus venosus like other cardiac pacemaker tissues.
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