A transition temperature for acetylcholine channel conductance in chick myoballs.

Abstract

The temperature dependence of ACh [acetylcholine] channel conductance (.gamma.) and channel open time (.tau.) was determined by analysing ACh induced membrane current fluctuations in voltage clamped chick embryo myoballs. As decreased [l/pohm] from 25-30 pmho in .gamma. at 37.degree. C to less than 5 phmo at 10.degree. C was found. An Arrhenius plot of .gamma. vs. temperature exhibited a clear break or transition temperature at 20.degree. C. An increase in .tau. from 2 ms at 37.degree. C to 16 msec at 10.degree. C was found. The Arrhenius plot of .tau. vs. temperature was linear. No transition temperature was detected. Submicellar concentrations of the non-ionic detergent, Triton X-100 reversibly blocked ACh responses. The effect was all-or-none at the molecular level. The fluidity of membrane lipids in the ACh receptor micro-environment may influence the degree to which the channel can open.