The transmitter role of glutamate in nervous systems.

Acceptance of L-glutamate as an excitatory transmitter was relatively slow compared to other transmitters, such as GABA. However, the transmitter role of L-glutamate has received more attention recently. In the crustacean neuromuscular junction L-glutamate fulfills most of the criteria for the transmitter identification. Studies on the glutamate receptor antagonist suggest that L-glutamate may also be the transmitter at the squid giant synapse. L-Glutamate may be the excitatory transmitter in many parts of CNS, although the evidence for this hypothesis is still not complete. The role of L-aspartate as the transmitter in CNS is not clear but its contribution may be less than that of L-glutamate. Glutamate receptors have been classified into three groups according to pharmacological properties. However, recent observations suggest that the situation seems more complicated than previously expected and more detailed comparison between synaptic potentials and glutamate action is needed.