title: N-methyl D-aspartate acts as an antagonist of the photoreceptor transmitter in the carp retina.
abstract: Glutamate, aspartate, and their agonists, kainate, quisqualate, cysteine sulfinate and N-methyl-D-aspartate (NMDA), were applied to the isolated carp retina while recording from horizontal cells. All these agents, except NMDA, depolarized horizontal cells membrane and reduced responses to light, thus mimicking the effect of the endogenous photoreceptor transmitter. Application of NMDA, on the other hand, caused a membrane hyperpolarization of horizontal cells in the dark, an effect different from its depolarizing effect as observed elsewhere in the central nervous system. NMDA also reduced or blocked the light responses of these cells as well as the depolarizing responses to applications of glutamate, aspartate or kainate. Effects of NMDA on the spectral properties of the horizontal cell responses were identical to the effects of the acidic amino acid receptor antagonists alpha-methyl glutamate, and alpha-amino adipate. Thus, NMDA appears to act as a weak antagonist to the photoreceptor transmitter, whose receptors on the horizontal cell membrane interact with a glutamate-like substance but appear atypical of glutamate receptors described elsewhere in the brain.
authors.forename: M
authors.initials: M
authors.lastname: Ariel
authors.forename: S C
authors.initials: SC
authors.lastname: Mangel
authors.forename: J E
authors.initials: JE
authors.lastname: Dowling
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D002347:Carps; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D016202:N-Methylaspartate; D009433:Neural Inhibition; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors*; D010775:Photic Stimulation; D010786:Photoreceptor Cells / Q000187:drug effects*; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter / Q000187:drug effects*; D012160:Retina / Q000187:drug effects* / Q000502:physiology
chemical_list: D005971:Glutamates; D018377:Neurotransmitter Agents; D016194:Receptors, N-Methyl-D-Aspartate; D017981:Receptors, Neurotransmitter; D001224:Aspartic Acid; D018698:Glutamic Acid; D016202:N-Methylaspartate; D007608:Kainic Acid