Fig. 4.
Effect of 5 µM TBB on the ImAHP during reproductive state is dependent on spike number. A: TBB increased the peak ImAHP to a much greater extent in OT neurons from virgin rats compared with both groups of pregnant animals with short, 3 spike trains. (K-W, 3 spike P ≤ 0.0001; *P ≤ 0.0001, virgin vs. E18–19; **P ≤ 0.046, virgin vs. E20–21). The effect of reproductive state was marginally significant at 10 spikes (K-W 10 spike P ≤ 055) with the significant difference lying between the virgin and E20–21 groups (***P ≤ 0.016), but was not significantly different with 17 spikes (K-W, P > 0.104). B: example traces from 3- and 17-spike trains in virgins and E20–21 pregnant rats showing the larger increase to TBB with the 3 spike trains (arrows). Note the difference in the time scales for 3 vs.17 spike trains. E18–19, embryonic days 18–19; E20–21, embryonic days 20–21; ImAHP, small-conductance Ca2+-activated potassium channel-mediated, medium afterhyperpolarization; K-W, Kruskal-Wallis; OA, okadaic acid; OT, oxytocin; TBB, 4,5,6,7-tetrabromobenzotriazole.