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결장뉴 전기활동도에 대한 칼슘 길항제의 영향

Effects of Ca<sup>2+</sup>-antagonists on the electrical activity of guinea-pig taenia coli

The influences of Ca<sup>2+</sup>-antagonists, verapamil and Mn<sup>2+</sup>, upon the spontaneous electrical activity and contractions were studied in guinea-pig taenia coli. Spontaneous contractions were recorded with force transducer, and spike action potentials were measured extracellularly by use of suction electrode. All experiments were performed in tris-buffered Tyrode solution Which was aerated With 100% O<sub>2</sub> and kept at 35℃. The results obtained were as follows : 1) Verapamil suppressed the frequency and amplitude of spontaneous contractions dose dependently, and blocked completely mechanical responses at the concentration of 1 mg/1. 2) The frequency of bursts of spike discharge(bursts frequency) and the number of spikes in a burst(spikes frequency) were reduced in a dose¡¤dependent manner within the concentration range of 10<sup>-5</sup> to 10<sup>-3</sup>g/l, and bursts frequency was affected more readily at a low concentration of 10<sup>-5</sup>g/l verapamil. 3) The verapamil<sub>i</sub>nduced suppression of spontaneous contractions in the Tyrode solution containing 1 mM Ca<sup>2+</sup> was completely antagonized by the addition of extra Ca<sup>2+</sup> to the Tyrode solution (2 m MCa<sup>2+</sup>). 4) Mn<sup>2+</sup> suppressed the amplitude of spontaneous contractions, whereas Mn<sup>2+</sup> accelerated the frequency dose-dependently within the range of low concentrations(10<sup>-7</sup> to 10<sup>-4</sup> M Mn<sup>2+</sup>). 5) The bursts frequency determining frequency of spontaneous contractions was increased in a dose-dependent manner, whereas the spikes frequency known to determine the contractions amplitude was reduced within the range of low concentrations. At a high concentration of 1 mM Mn<sup>2+</sup>, however, all spontaneous contractile responses were blocked simultaneously with the disapperance of electrical activity. 6) The frequency and amplitude of spontaneous contractions altered by Mn<sup>2+</sup> in 1mM Ca<sup>2+</sup> Tyrode were increased by extra Ca<sup>2+</sup>(2mM).

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