Small artificial currents enhance Xenopus limb regeneration

A steady, small (0.1 μA) current was artificially pulled out of the end of the stumps of amputated adult Xenopus forelimbs for three to four weeks. Six months to a year later, the following responses were observed: 1. Some stimulated regenerates formed broad, flattened bifurcated structures, while sham‐treated controls formed typical hypomorphic spikes. 2. In the majority of the cathode‐stimulated regenerates, there were nerve trunks with in their cartilage core. There was no nerve in control cartilage, except in one case in which a small amount of nerve was found. Overall, the cartilage core of the stimulated regenerates had 40‐fold more nerve coursing through it than did the controls. 3. Mature thorn‐shaped epidermal papillae formed on most of the stimulated animals, but on only one of the controls. We suggest that these minute electrical currents affect regeneration by first stimulating early nerve growth.