ABSTRACT
It is now more than 45 years since a series of papers from the laboratory of Bernard Katz established, using electrophysiological techniques, that calcium controls the amount of transmitter released at individual nerve terminals. First, del Castillo and Stark (1952) showed that changing the external calcium concentration changed the size of the endplate potential recorded with an extracellular electrode without changing the response of the endplate to exogenously applied acetylcholine. Second, the changes in amplitude of the endplate potential with changes in calcium concentration were then confirmed using the recently invented intracellular microelectrode by Fatt and Katz (1952a). Finally, Fatt and Katz (1952b) discovered the spontaneous miniature endplate potentials and showed that while changes in the calcium concentration altered the amplitude of the endplate potential it did not affect the miniature endplate potentials. This lead to the concept that the endplate potential consists of multiples of miniature endplate potentials, each termed a quantum, the actual number of which is determined by the calcium ion concentration. In this historical essay, the development of ideas concerning the role of calcium in transmitter release is described, together with the efforts to identify the sensor for calcium which triggers transmitter release.
