Abstract
Effects of cooling on depolarized smooth muscle were studied using guinea-pig was deferens.
Cooling treatment of high-K-depolarized preparation caused tesion development. The maximum tension was observed by coolin the preparations from 35°C to 20°C. Lowering the temperature below 10°C caused relaxation of the preparations. No change or only a small change in membrane potential was observed by cooling, whereas the membrane resistance increased. Rapid cooling caused a phasic contraction followed by sustained tonic contraction.
The tension development was sensitive to extracellular Ca and no tension development was observed by cooling the preparation in Ca-free solution. The increase in Ca concentration of K-Tyrode solution caused further increase in tension development by cooling, whereas it caused only a small increase in tension at 35°C
It was suggested that the tension development would be caused by the inhibition of Ca extrusion through cell membrane (Ca pump), but not by the increase in Ca influx.
