Expression of functional sodium channels in stage II–III Xenopus oocytes

Abstract

We have injected mRNA from rabbit brain into stage II–III Xenopus oocytes to determine whether they will translate exogenous RNA and incorporate functional ion channels into the membrane. Our results show that 48 h after RNA injection, functional voltage-dependent Na channels are present at sufficient densities to allow quantitative electrophysiological recording. The smaller oocytes have at least 2 experimental advantages over the stage V–VI oocytes normally used for electrophysiological experiments: (1) the smaller membrane capacitance (approximately 5-fold) allows a faster settling time following a voltage step and a more detailed kinetic analysis of membrane currents than was previously possible with the 2-microelectrode technique, and (2) roughly 8-fold less RNA is needed for each injection. Thus, the stage II–III Xenopus oocyte is a suitable preparation for the study of ion channels.