SINGLE-CHANNEL CURRENTS FROM ZONA-FREE MOUSE EGGS

¹ Department of Preclinical Veterinary Sciences, R.(D).S.V.S., Summerhall, University of Edinburgh EH9 1QH

Cell-attached patch recordings were made from zona-free mouse eggs to examine currents at the single-channel level; two types were identified. A channel with a mean conductance of 130 pS showed changes in reversal potential on dilution of the patch pipette solution consistent with a cation channel; the channel current persisted when the only cation in the pipette was K⁺: it was concluded that this channel was permeable to K⁺. The binomial distribution was used to describe the proportion of time 0, 1, 2, ..., n channels were open in multichannel recordings of the K⁺ channel. Bursts of inward currents of about 1 pA, which showed voltage activation and could be recorded in the presence of CsCl and tetraethylammonium (TEA), were identified as Ca²⁺ channels.