Figure 4. Effects of 2-aminoethoxydiphenyl borate (2-APB) and La³⁺ on slow potentials.

During simultaneous recordings of membrane potential from two cells in a segment of circular smooth muscle tissue from the guinea-pig gastric antrum, 1 s current pulses (A and B, 3.0 nA; C and D, 2.5 nA) were applied to one electrode, and evoked slow potentials were recorded in the absence (A, C) and presence of 5 μM 2-APB (B) or 30 μM La³⁺ (D). The amplitudes of responses evoked in the second electrode were plotted as a function of the interval between the cessation of a spontaneous slow potential and the initiation of a current pulse, in the absence and presence of 5 μM 2-APB (E) or 30 μM La³⁺ (F). Mean amplitudes (mean ± s.d.) of slow potentials generated in the absence (•) and presence of 2-APB or La³⁺ (○) are shown at the left hand side of each figure (E, n = 19 for 2-APB, P < 0.05; F, n = 23 for La³⁺, P > 0.05).