Transient changes in electrical potential differences across frog skin

The time course of changes in potential difference across frog skin ( Rana pipiens) following rapid changes in composition of the bathing solutions has been investigated. Increasing Na concentration in the outside solution results in a rapid rise in potential difference which is nearly complete in 0.4–0.5 sec. Analysis of the time course of this change strongly suggests the presence of a barrier to Na movement located quite near the anatomical outside of the skin. The change in potential difference following changes in the K concentration of the inside solution is much slower, and is consistent with the location of the K-sensitive barrier 150–250 µ from the inner surface of the skin.