The concept of a calcium sensor in transmitter release

The discovery was made in the 1940s that calcium is required for transmitter release at synapses, raising the question of the identity of the sensor molecule upon which this calcium acts. Subsequently it was shown in the 1960s that this calcium acts on the inside of the nerve terminal. The channels which mediate the influx of calcium ions into the nerve terminal were identified in the 1970s. This essay is concerned with tracing the development of the concept of a calcium sensor in nerve terminals and of recent work that identifies the sensor molecule as synaptotagmin.