CHLORIDE CHANNELS IN SKELETAL-MUSCLE AND CEREBRAL CORTICAL-NEURONS

The advent of single-channel methods has led to the discovery of many different types of Cl channels in excitable tissues, such as nerve and muscle. Ion channels selective for Cl have been found in a variety of mammalian tissues, including muscle, nerve, endocrine, exocrine gland, and epithelium. Several types of mammalian Cl channels have been cloned and their primary sequences determined. This chapter discusses the properties of Cl channels that have been identified at the single-channel level in cells from two excitable mammalian tissues, skeletal muscle, and cerebral cortical neurons. Two Cl-selective ion channels have been discovered in tissue-cultured rat skeletal muscle that potentially could contribute to the resting Cl conductance. Both these channels are selective for Cl and could be active at normal negative membrane potentials. Single channel current traces, obtained with the patch-clamp technique, for both these channels, this is discussed in the chapter. One channel is “slow Cl channel” and the other is “fast Cl channel.” Cl channels, with properties, very similar to those of the fast Cl channels found in tissue-cultured skeletal muscle have been reported in acutely dissociated rat cerebral cortical neurons. The ion selectivity, voltage dependence, and kinetic activity of these neuronal fast Cl channels are nearly identical to their muscle counterparts. The stability of the gating of neuronal fast Cl channels makes them ideal objects for the study of single-channel kinetics. The way is now clear for the application of the techniques of molecular biology that have led to molecular models for cation channels to be applied to anion channels as well. © 1994 Academic Press, Inc.