The rise and fall of electrical excitability in the oocyte of Xenopus laevis.

1. An electrically excited (gated) sodium selective channel has been found in the Xenopus laevis oocyte, a cell membrane previously considered non-excitable. 2. The channel is produced by prolonged depolarization of the membrane and is removed by prolonged repolarization. Both processes are very dependent on temperature and potential. 3. Once produced, the channel can be opened and closed electrically, but does not show inactivation as is found in other sodium selective channels. 4. The sodium selectivity and the electrical gating properties of this channel make it a potentially useful candidate for the study of these general channel characteristics. The fact that this membrane can be made to show these properties reversibly offers the possibility of the studying the origins of this channels.