An electrophysiological analysis of the effects of cooling on autonomic neuromuscular transmission in the guinea-pig vas deferens.

The effects of cooling upon the excitatory junction potential (e.j.p.) and spontaneous e.j.p.s. in the guinea-pig vas deferens have been studied. A series of strict criteria have been used to select 'successful' penetration of smooth muscle cells by the micro-electrodes. Cooling the vas from 35 to 22 degrees C has little effect on the membrane potential. The e.j.p. is increased in size by cooling from 5 . 1 +/- 0.2 mV, n = 120 at 35 degrees C to 15 . 9 +/- 0 . 5 mV, n = 29 at 22 degrees C. Facilitation is less marked at lower temperatures. The effects of cooling are not due to any effects under the electrodes used to stimulate the innervation of the vas. The frequency and size of spontaneous e.j.p.s. is reduced by cooling. The significance of these observations is discussed.