Characterization of AMPA receptors on isolated amacrine-like cells in carp retina.
In amacrine-like cells freshly dissociated from crucian carp (Carassius auratus) retina, we recorded whole-cell responses to rapid application of glutamate and kainate. Currents induced by glutamate, but not kainate, usually showed extremely rapid desensitization, and the mean time constant for the decay of the responses to 10 mM glutamate was 2.77 ms. N-methyl-D-aspartate (NMDA) failed to induce any current even with coapplication of glycine and removal of extracellular Mg2 +. 1-(4-aminophenyl)-3-Methylcarbamyl-4-methyl-7,8-methylenedioxy-3, 4-dihydro-5H-2,3-benzodiazepine (GYKI 53655), a selective alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor antagonist, was found to completely block glutamate-induced currents, suggesting that the glutamate receptors on these cells are AMPA preferring. The value of EC50 for glutamate and kainate was determined to be 2.73 mM and 97.5 microM, respectively. Noise analysis of fluctuation of whole-cell currents induced by kainate of different concentrations indicated that the mean conductance of the AMPA receptor channels was 5.70 pS. Splice variant analysis of the AMPA receptors was also conducted by comparing the effects of cyclothiazide, a flip receptor-preferring modulator and 4-[2-(phenylsulphonylamino)ethylthio]-2,6-difluoro-phenoxyaceta mide (PEPA), a flop receptor-preferring modulator, on glutamate-induced responses. PEPA was much more potent than cyclothiazide at these receptors with a EC50 of 17.3 microM. The mean ratio of the potentiation by PEPA versus cyclothiazide (P/C ratio) was 4.39. These modulatory effects of cyclothiazide and PEPA were rather similar to those obtained at AMPA receptors assembled from flop variants expressed in Xenopus oocytes, suggesting that the AMPA receptor of the carp amacrine cells may predominantly consist of the flop splice variants.
Shen
Y
Y
Shanghai Institute of Physiology and Key Laboratory of Neurobiology, Chinese Academy of Sciences, China.
Zhou
Y
Y
Yang
X L
XL
D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001569:Benzodiazepines / Q000494:pharmacology; D001581:Benzothiadiazines / Q000494:pharmacology; D002469:Cell Separation; D004305:Dose-Response Relationship, Drug; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D006054:Goldfish; D007473:Ion Channels / Q000187:drug effects; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D016202:N-Methylaspartate / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010642:Phenoxyacetates; D018091:Receptors, AMPA / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000378:metabolism* / Q000502:physiology
C108189:4-(2-(phenylsulfonylamino)ethylthio)-2,6-difluorophenoxyacetamide; D000959:Antihypertensive Agents; D001581:Benzothiadiazines; D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D007473:Ion Channels; D010642:Phenoxyacetates; D018091:Receptors, AMPA; D001569:Benzodiazepines; C079692:GYKI 53655; D018698:Glutamic Acid; D016202:N-Methylaspartate; C004639:cyclothiazide; D007608:Kainic Acid