Calcium Channels

Abstract

This chapter discusses the different types and tools to characterize calcium channels. It focuses on the voltage-dependent calcium channels in plasma membranes from mammalian electrically excitable cells. The calcium channel drugs are treated as structural and functional tools. The chapter also presents some electrophysiological studies of calcium channels. Calcium channels are among the Methuselahs of ion channels. The diversity and the complexity of the physiological control and pharmacological modulation of the calcium channel family have become apparent. The plasma membrane of excitable cells contains several types of calcium channels. They are distinguished by voltage dependence, unitary conductance, selectivity, and by pharmacology. In many cells, multiple channel types are observed, but there are also some membranes where only one type appears to exist. The different types (termed L, T, and N) are well characterized, especially in heart and neuronal tissue. The L type is predominant in heart and smooth muscle cells; the L, T and N types are found in nerve cells. The calcium channels can be characterized biochemically only by specificity of drug binding.