Figure 4.

The distribution of intervals between successive spontaneous depolarizations (Aa) demonstrates that under control conditions they occur randomly, as the control distribution (solid line, black) follows the expected exponential distribution (dashed line, black). In the presence of PGE₂ (50 µM), bursting occurs, shown by the excess of brief intervals compared with the expected exponential distribution (compare the dashed and solid grey lines). (Ab) The median intervals were also briefer in the presence of PGE₂. (B) PGE₂ also stimulated an increase in spontaneous depolarization frequency (a), an increase in rise time (c) and amplitude (d), and a depolarization of the RMP of SMCs (b). The data were obtained from n_p = 13 and n_a = 12 (Ab, B); *P < 0.05 and ***P < 0.001.