Temperature-dependency of pacemaker activity in gastric smooth muscle

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In isolated gastric smooth muscle tissue of the guinea-pig, the effects of changes in temperature and their modulation by metabolic inhibitors on slow waves were investigated, to understand the possible involvement of metabolic processes in the pacemaker activity of spontaneous activity of gastric smooth muscle tissues. Experiments were carried out to record spontaneously generating electrical responses from circular and longitudinal smooth muscle cells and interstitial cells of Cajal, in small pieces of gastric smooth muscle tissues isolated from the guinea-pig, during changing temperature between 24 and 42 ℃. With elevation of temperature, the frequency and the speed of rate of rise were increased in slow waves, follower potentials and pacemaker potentials, while the duration of these potentials was reduced. These changes were related with the elevation of temperature in a linear way. The latency for generating the 2nd component of slow wave was decreased in an exponential way betwee … More n 24 and 32 ℃, while it remained unchanged above 32 ℃. The resting membrane potential and amplitude of slow waves were not sensitive to temperature. Calculation of temperature co-efficiency (Q10 value) indicated that it was higher on the frequency, duration and rate of rise of slow waves. Potassium cyanide (KCN), an inhibitor of mitochondrial metabolic activity, inhibited only the changes in frequency, but not the duration and rate of rise time, of slow waves in response to temperature. These results suggested that the factors determining the frequency of slow waves alone are causally related to the mitochondrial metabolic activity. As the duration and the rate of rise time of slow waves were not altered by KCN, possible contribution of factors other than mitochondrial metabolism was considered for their determination. The regulation of the activity of entire stomach might be the most active region, and it was found to be the corpus region of the stomach. The corpus region produced slow waves 4-6 times every min, and they had strong potential-dependency, suggested a possible involvement of factors other than mitochondria for regulation of the activity. Less