Ion channels in presynaptic nerve terminals and control of transmitter release

The primary function of the presynaptic nerve terminal is to release transm itter quanta and thus activate the postsynaptic target cell. In almost ever y step leading to the release of transmitter quanta, there is a substantial involvement of ion channels. In this review, the multitude of ion channels in the presynaptic terminal are surveyed. There are at least 12 different major categories of ion channels representing several tens of different ion channel types; the number of different ion channel molecules at presynapti c nerve terminals is many hundreds. We describe the different ion channel m olecules at the surface membrane and inside the nerve terminal in the conte xt of their possible role in the process of transmitter release. Frequently , a number of different ion channel molecules, with the same basic function , are present at the same nerve terminal. This is especially evident in the cases of calcium channels and potassium channels. This abundance of ion ch annels allows for a physiological and pharmacological fine tuning of the pr ocess of transmitter release and thus of synaptic transmission.