Figure 1. The effects of gap junction blockers on swimming bursts and the electrical coupling of hindbrain dINs of Xenopus embryos.

Aa, Xenopus tadpole at stage 37/38, from Nieuwkoop & Faber (1956). Ab and c, effects of two gap junction blockers, 18β-GA (90 μm) and CBNX (100 μm), and d, a time control, on ventral root bursts during fictive swimming. B, the increase in ventral root burst durations in 18β-GA correlates temporally with the blocking of electrical coupling between hdINs. Ba, ventral root burst duration measured on the 10th cycle at the beginning of each swimming episode after applying 40 μm 18β-GA; grey: individual measurements from 6 preparations; black: mean durations ±s.d.; Bb, normalised average electrical coupling coefficients (same preparations as Ba) after 18β-GA applied at time zero (see Li et al. 2009). Bc, burst durations measured on the 10th cycle at the beginning of each swimming episode do not change with time under control conditions; grey: individual measurements from 5 preparations; black: average durations ±s.d. Bd, simultaneous whole-cell patch recordings of coupled dINs in control (left column) and after 18β-GA treatment (right column). Upper trace: one example of the 10th ventral root bursts from the beginning of swimming before and after 18β-GA blockade; lower traces: responses of two coupled dINs to hyperpolarizing current injected in either cell. Recording time points of control and block examples were indicated by left and right arrows in Ba, respectively.