New Evidence That L‐glutamate Is a Transmitter at the Squid Giant Synapse

Experiments are described showing unequivocally that transmission at the squid giant synapse can be reversibly blocked by L-glutamate and its agonists kainate, quisqualate and AMPA, though not by NMDA. This effect is presumably brought about by desensitization. The glutamate antagonists cis-2,3-PDA, GAMS and the new quinoxalinediones CNQX and DNQX are also potent reversible blockers. These findings provide new evidence that L-glutamate is a transmitter at the giant synapse and further suggest that the glutamate receptor may be of the non-NMDA type.