Figure 3. Modulation of refractory period for slow potentials by inhibition of PKC.

In a circular muscle bundle, isolated from the antrum of guinea-pig stomach, depolarizing current stimulation (3 nA intensity, 1.5 s duration) was applied in the absence (A and B) and presence of 0.3 μm chelerythrine (C and D). In control conditions, stimulation at about 4 s (A) did not, but at 5.5 s (B) did produce slow potential, while in the presence of chelerythrine, stimulation at about 20 s (D) did but at 12 s (C) did not evoke slow potential. The relationship between the time of stimulation after cessation of current stimulation and amplitude of the evoked response (•, control; ○, in the presence of chelerythrine) indicates that the threshold time for the generation of slow potential (T1, equal to refractory period) was increased by about 3 s (T2) by chelerythrine (E).