Pharmacology of ionic channels in excitable membranes.

Methods are now available for recording the behaviour of single ion channels in biological membranes. These include patch clamp, noise analysis and voltage-jump techniques. Their use is illustrated at the motor end-plate where it has been shown that the decay of end-plate currents is determined by the rate of closing of channels opened by acetylcholine. The effects of a variety of pharmacological agents can be explained in terms of changes in channel behaviour. Drugs may change the properties of the channel or its environment, block open channels or prolong the lifetime of acetylcholine in the synaptic cleft. Voltage-activated channels can also be characterised using patch clamp and noise analysis. A variety of drugs block sodium, potassium and calcium channels.