Effects of rapid cooling on the electrical properties of the smooth muscle of the guinea-pig urinary bladder.

The effects of low temperature (36-10 degrees C) on the electrical properties of smooth muscle cells of the urinary bladder were investigated with microelectrodes and the double sucrose gap method.1. Lowering the temperature from 36 to 20 and to 10 degrees C, depolarized the membrane from -37 to -33 and to -25 mV respectively. Spontaneous and propagated spike activity ceased completely at below 20 degrees C but evoked spikes were occasionally observed at 10 degrees C. A sustained contracture was evoked below 25 degrees C.2. At both normal and low temperatures, the tissue had cable-like properties. The length constant was reduced from 1.82 mm (36 degrees C) to 1.54 mm (20 degrees C) and to 1.04 mm (10 degrees C). On the other hand, the time constant of the membrane calculated from the cable equations was prolonged by lowering the temperature from 157 msec (36 degrees C) to 257 msec (20 degrees C) and to 508 msec (10 degrees C). The effective resistance of the membrane was increased to 1.8 times at 20 degrees C and to 2.9 times the control value at 10 degrees C.3. From the changes in various parameters of the membrane at low temperature, an increase in the longitudinal resistance of the tissue was postulated.4. The possible mechanisms of action of low temperature on the electrical properties of the smooth muscle of the urinary bladder were discussed in relation to those of the taenia coli and stomach, especially on the effects of low temperature on the sequestered Ca in the cell.