Nobel lecture. Ion channels for communication between and within cells.

Around 1970 the fundamental signal mechanisms for communication between cells of the nervous system were known. Hodgkin and Huxley (1952) had provided the basis for understanding the nerve action potential. The concept of chemical transmission at synapses had received its experimental verification by detailed studies on excitatory and inhibitory postsynaptic potentials (see Katz, 1966, for a concise description of the electrical signals in nerve and muscle). The question of the molecular mechanisms underlying these signals was still open, however. Hodgkin and Huxley (1952) used the concept of voltage-operated gates for a formal description of conductance changes, and by 1970 the terms Na-channel and K-channel were used frequently (see review by Hille, 1970), although no direct evidence for the existence of channels was available from biological preparations. This was different for the case of artificial membranes. Miiller and Rudin (1963) introduced "black-lipid membranes" as experimental model systems, which in many respects resemble the bimolecular lipid membrane of living cells. These membranes are rather good insulators. However, when they are doped with certain antibiotics or proteins they become electrically conductive. Bean et al. (1969) and Hladky and Haydon (1970) showed that some of these dopants induce discrete, steplike changes in conductance when they are added in trace amounts. All the evidence suggested that the conductance changes observed represent the insertion of single pore-like structures into the membranes.