The contribution of NMDA and non-NMDA receptors to the light-evoked input-output characteristics of retinal ganglion cells.
To examine how light-evoked excitatory synaptic inputs to retinal ganglion cells are transformed into output patterns of activity, action potentials were recorded with cell-attached patch-clamp techniques, and then EPSCs and EPSPs were recorded from the same cell in the whole-cell configuration. AP7, an NMDA antagonist, reduced the light-evoked peak spike frequency 36% +/- 21% (mean +/- SD) and reduced the EPSC amplitude, indicating a major role for NMDA receptors in the light response. CNQX, a non-NMDA receptor antagonist, reduced the light-evoked peak spike frequency 28% +/- 22%. CNQX also caused a voltage- and magnesium-dependent delay in spike onset. AP7 and CNQX, however, did not differ significantly in their effect on the EPSC time course, indicating that postsynaptic cellular properties are responsible for the delay observed in the presence of CNQX. These results show that the NMDA receptor contribution to the excitatory response is increased as the cell is depolarized from rest by non-NMDA input.
Diamond
J S
JS
Bioengineering Graduate Group, University of California, San Francisco 94143-0730.
Copenhagen
D R
DR
D015763:2-Amino-5-phosphonovalerate / Q000031:analogs & derivatives*; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000557:Ambystoma; D000596:Amino Acids / Q000494:pharmacology*; D000818:Animals; D003624:Darkness; D004594:Electrophysiology / Q000379:methods; D005071:Evoked Potentials / Q000187:drug effects / Q000528:radiation effects; D018691:Excitatory Amino Acid Antagonists; D066298:In Vitro Techniques; D008027:Light; D008274:Magnesium / Q000494:pharmacology; D008433:Mathematics; D008959:Models, Neurological; D010775:Photic Stimulation; D011810:Quinoxalines / Q000494:pharmacology*; D017470:Receptors, Glutamate / Q000502:physiology; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D013569:Synapses / Q000187:drug effects / Q000502:physiology*
D000596:Amino Acids; D018691:Excitatory Amino Acid Antagonists; D011810:Quinoxalines; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D015763:2-Amino-5-phosphonovalerate; D008274:Magnesium; C031231:2-amino-7-phosphonoheptanoic acid