Amino Acid Transmitters

This analysis focuses on synapses where a transmitter or “mediator” function of amino acids is considered to be very likely and amino acids well suited to this function.

Abstract

Appreciable amounts of amino acids occur free in both vertebrate and invertebrate nervous systems. It is generally accepted that these are predominantly concerned with general metabolic processes, and with the maintenance of water and ion distributions across cellular membranes: however, certain amino acids may also function as synaptic transmitters. Recent reviews catalogue the many sites at which excitant or depressant actions of a variety of amino acids have been demonstrated,(1–3) and it is intended to restrict this present analysis to synapses where a transmitter or "mediator" function of amino acids is considered to be very likely. Prior to discussing the function of specific amino acids at particular synapses, the processes involved in synaptic transmission are outlined, together with general problems relating to transmitter function and the techniques available for their investigation. It is not intended to discuss "modulator" substances which have been postulated to function as regulators of the activity of neurons or effector cells, but which are not essential for synaptic transmission;(2,4) amino acids may be well suited to this function.