AMPA-preferring receptors mediate excitatory synaptic inputs to retinal ganglion cells.
Pharmacological studies were performed to determine whether alpha-amino-3-hydroxy-5-methyl-4-isoazoleprionic acid (AMPA)- and/or kainate (KA)-preferring receptors mediate excitatory synaptic inputs to tiger salamander retinal ganglion cells. Excitatory postsynaptic currents (EPSCs), evoked either by light or by stimulating bipolar cells with puffs of K+, were measured using whole cell recording techniques in the tiger salamander retinal slice. The AMPA/KA component of the EPSCs was isolated by including antagonists of glycine-, gamma-aminobutyric acid (GABA)- and NMDA-receptors in the bath. The AMPA-preferring receptor antagonists, 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine hydrochloride (GYKI-52466) and 1-(4-aminophenyl)-3-methylcarbamyl-4-methyl-7,8-methylenedioxy-3,4 - dihydro-5H-2,3-benzodiazepine (GYKI-53665), reduced light-evoked EPSCs and K+ puff-evoked EPSCs amplitudes in a concentration-dependent manner. The IC50 values for GYKI-52466 were 3.6 and 4.2 microM for the light- and puff-evoked responses, respectively. The more potent GYKI-53665 had IC50 values of 0.7 microM for both the light- and puff evoked responses. KA activates both KA- and AMPA-preferring receptors. KA-evoked currents were completely blocked by 10-40 microM GYKI-53665, indicating that little or no excitatory synaptic current was mediated by KA-preferring receptors. Concanavalin A, a compound that preferentially potentiates responses mediated by KA-preferring receptors, did not enhance either EPSCs or glutamate-evoked responses. By contrast, cyclothiazide, which selectively enhances AMPA-preferring receptor mediated responses, was found to enhance both EPSCs and glutamate-evoked currents. Our results indicate that the non-NMDA component of ganglion cell EPSCs is mediated by AMPA-preferring receptors and not significantly by KA-preferring receptors.
Lukasiewicz
P D
PD
Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110-1093, USA.
Wilson
J A
JA
Lawrence
J E
JE
D000557:Ambystoma; D000818:Animals; D014151:Anti-Anxiety Agents; D001569:Benzodiazepines / Q000494:pharmacology; D003712:Dendrites / Q000187:drug effects; D004594:Electrophysiology; D005074:Evoked Potentials, Visual / Q000187:drug effects / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008839:Microelectrodes; D018408:Patch-Clamp Techniques; D010775:Photic Stimulation; D011188:Potassium / Q000494:pharmacology; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*; D017981:Receptors, Neurotransmitter / Q000187:drug effects / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000502:physiology*; D013268:Stimulation, Chemical
D014151:Anti-Anxiety Agents; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; C105194:GYKI 53665; D018091:Receptors, AMPA; D017981:Receptors, Neurotransmitter; C061950:GYKI 52466; D001569:Benzodiazepines; D011188:Potassium