Self-generated electrical currents through Xenopus neurulae.

An extracellular vibrating electrode has been used to investigate epithelial current production by Xenopus neurulae. Xenopus neurulae, in 5% DeBoer (DB) solution, stages 14-22, generated an endogenous current which left the blastopores of the embryos, and entered all other locations. The inward current declined near the mid line of the neural groove in stage 15 embryos. The inward current was abolished or drastically reduced by exchange of 5% DB with Na+-free (choline- or bis(2-hydroxyethyl)dimethylammonium (BDAC)-substituted) 5% DB, 5.5 mM-KCl, 1 mM-verapamil in 5% DB, 50 or 500 microM-ouabain in 5% DB, or 1 microM-amiloride in 5% DB. Verapamil (10 microM) in 5% DB, 5.5 mM-NaCl and 1 mM-CoCl2 in 5% DB had little or no effect on the magnitude observed. The current also was present in 5% DB containing Li+ instead of Na+; current carried by Li+ was abolished by amiloride. This is consistent with a Na+ current, similar to that of short-circuited adult frog skin.