Effects of glutamic acid and related agents on horizontal cells in a marine teleost retina

Excitatory amino acids (EAAs) such as glutamic and aspartic acids, considered as the most likely neurotransmitters at the photoreceptor-horizontal cell synapse of teleost retinas, as well as agonists such as kainic acid and several of their antagonists, were applied to isolated and superfused retinas of the teleost Eugerres plumieri. Intracellular recordings from horizontal cells reveal that EAA receptors are of the kainate-quisqualate type. There is competitive inhibition between the agonist and antagonist agents used, and under their combined effect, the synapse under study remains operational, in a functional state, able to modulate the horizontal cell membrane potential upon retinal illumination.