Document Detail

Modulation of desensitization at glutamate receptors in isolated crucian carp horizontal cells by concanavalin A, cyclothiazide, aniracetam and PEPA.
MedLine Citation:
PMID:  10199629     Owner:  NLM     Status:  MEDLINE    
In horizontal cells freshly dissociated from crucian carp (Carassius auratus) retina, we examined the effects of modulators of glutamate receptor desensitization, concanavalin A, cyclothiazide, aniracetam and 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetam ide (PEPA), on responses to rapid application of glutamate and kainate, using whole-cell voltage-clamp techniques. Incubation of concanavalin A suppressed the peak response but weakly potentiated the equilibrium response of horizontal cells to glutamate. Cyclothiazide blocked glutamate-induced desensitization in a dose-dependent manner, which resulted in a steady increase of the equilibrium current. The concentration of cyclothiazide causing a half-maximal potentiation for the equilibrium response was 85 microM. Furthermore, cyclothiazide shifted the dose-response relationship of the equilibrium current to the right, but slightly suppressed the kainate-induced sustained current. These effects of concanavalin A and cyclothiazide are consistent with the supposition that glutamate receptors of carp horizontal cells may be an alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-preferring subtype. In order to further characterize the AMPA receptors of horizontal cells, modulation by aniracetam and PEPA of glutamate- and kainate-induced currents was studied. Aniracetam, a preferential modulator of flop variants of AMPA receptors, considerably blocked desensitization of glutamate-induced currents, but only slightly potentiated kainate-induced currents. It was further found that PEPA, a flop-preferring allosteric modulator of AMPA receptor desensitization, slightly suppressed the peak current, while it dramatically potentiated the equilibrium current induced by glutamate in a dose-dependent manner. PEPA was much potent than aniracetam at these receptors and showed the effect on glutamate-induced desensitization even at a concentration as low as 3 microM. PEPA also potentiated non-desensitizing currents induced by kainate, but with much less extent. These modulatory effects of concanavalin A, cyclothiazide, aniracetam and PEPA on AMPA receptors in carp horizontal cells were rather similar to those obtained at AMPA receptors assembled from flop variants expressed in Xenopus oocyte and HEK cell. Consequently, we speculate that the AMPA receptor on carp horizontal cells may predominantly carry the flop splice variants.
Y Shen; T Lu; X L Yang
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Neuroscience     Volume:  89     ISSN:  0306-4522     ISO Abbreviation:  Neuroscience     Publication Date:  1999 Mar 
Date Detail:
Created Date:  1999-07-07     Completed Date:  1999-07-07     Revised Date:  2009-11-19    
Medline Journal Info:
Nlm Unique ID:  7605074     Medline TA:  Neuroscience     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  979-90     Citation Subset:  IM    
Shanghai Institute of Physiology and Key Laboratory of Neurobiology, Chinese Academy of Sciences.
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MeSH Terms
Aspartic Acid Endopeptidases / pharmacology*
Benzothiadiazines / pharmacology*
Concanavalin A / pharmacology*
Goldfish / metabolism*
Nootropic Agents / pharmacology
Patch-Clamp Techniques
Pyrrolidinones / pharmacology*
Receptors, AMPA / drug effects
Receptors, Glutamate / drug effects*
Receptors, Kainic Acid / drug effects
Reg. No./Substance:
0/Benzothiadiazines; 0/Nootropic Agents; 0/Pyrrolidinones; 0/Receptors, AMPA; 0/Receptors, Glutamate; 0/Receptors, Kainic Acid; 11028-71-0/Concanavalin A; 2259-96-3/cyclothiazide; 72432-10-1/aniracetam; EC 3.4.23/aspartic proteinase A; EC 3.4.23.-/Aspartic Acid Endopeptidases

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