[Effect of antagonists of excitatory amino acids on synaptic transmission in the electroreceptors (Lorenzini's ampullae) in skates].

Ampullae of Lorenzini isolated from the skate (Raja clavata) have been investigated in vitro electrophysiologically to determine the nature of the transmitter at the synapse between the electroreceptor cells and afferent fibres. Glutamic acid diethyl ester (GDEE), glutamic acid dimethyl ester (GDME), kynurenic acid (KENYA), cis-2,3-piperidine dicarboxylic acid (PDA) reversibly decreased the resting and stimulus-induced activity. These antagonists also blocked postsynaptic responses induced by glutamate and aspartate. D-alpha-aminoadipic acid (DAA) had no effect on the afferent activity. These findings suggest that glutamate, aspartate or a related compound may be a transmitter at this synapse. An important physiological role of quisqualate receptors in ampullae of Lorenzini is also inferred from these experiments.