L-homocysteic acid selectively activates N-methyl-D-aspartate receptors of rat retinal ganglion cells.
To explore the possible role of L-homocysteic acid (HCA) as a retinal transmitter, whole-cell recordings with patch electrodes were performed on isolated rat retinal ganglion cells (RGCs) in culture. HCA elicited an inward current at -60 mV. Similar to currents evoked at this potential in RGCs by N-methyl-D-aspartate (NMDA), HCA-activated currents were of relatively small amplitude (10-150 pA), and the noise level increased dramatically during the response. When HCA was co-applied with concentrations of NMDA that elicited a maximal response, the current was not increased over that of NMDA alone. HCA-evoked currents were almost completely blocked by the NMDA antagonists D-2-amino-5-phosphonovalerate (D-AP5), Mg2+, or 7-chlorokynurenate (7-Cl KYN). Unlike its effects on other preparations, even millimolar concentrations of HCA did not activate kainate-like currents. These observations suggest that HCA specifically activates the NMDA receptor-channel complex of rat RGCs.
Department of Neurology, Children's Hospital, Boston, MA.
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Lipton
D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D005071:Evoked Potentials / Q000187:drug effects; D005998:Glycine / Q000502:physiology; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D007736:Kynurenic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects*; D012165:Retinal Ganglion Cells / Q000187:drug effects*; D013268:Stimulation, Chemical
D016194:Receptors, N-Methyl-D-Aspartate; D006710:Homocysteine; C007956:homocysteic acid; D015763:2-Amino-5-phosphonovalerate; D007736:Kynurenic Acid; C057013:7-chlorokynurenic acid; D005998:Glycine