Fig. 1. (A) Schematic diagram of the preparation used to initiate and monitor skin impulses in stage 37/38 Xenopus embryos. SKC (sharp), sharp microelectrode for intracellular recording from skin cells; SKC (patch), patch microelectrode for intracellular recording from skin cells; SKC (ext), extracellular recording suction electrode on skin; Stim (ext), extracellular stimulating suction electrode on skin; VR (ext), extracellular recording suction electrode on ventral root; YS, yolk sac. Scale bar, 1 mm. (B) Intracellular recording from a skin cell with a sharp microelectrode (lower trace) reveals a long duration impulse that is approximately coincident with a multi-phasic impulse recorded extracellularly from a nearby patch of skin (upper trace). (C) Intracellular recording with a patch microelectrode (lower trace) reveals a skin impulse with a similar shape to that recorded with a sharp microelectrode, except that the rising phase is faster. The same stimulus that initiates a skin impulse initiates swimming monitored by an extracellular recording from the ventral root (upper trace). (B,C) The broken horizontal line is set at 0 mV. The asterisk indicates the time of the stimulus.