Fig. 9.

The swimming pattern is relatively insensitive to catechol. Records of ventral root activity on the two sides of the embryo (vrl, vrr, left and right ventral root records, respectively) show that 10 μm catechol (A), which is near the IC₅₀ for block of the fast current, has little effect on swimming; 100 μm catechol (B) caused some abnormalities in the pattern, with discharge absent on some cycles (*). Segments illustrated are taken 8 sec from the electrical skin stimulus that initiated the swimming episode.