Regional distribution of alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid binding sites in rat brain: effect of chemical modification of SH- groups in tissue sections.
Previous studies have shown that chemical modifications of sulfhydryl (SH-) groups with mercurial compounds in rat brain membrane preparations increase the binding of alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid [(3H]AMPA), a ligand for the quisqualate/AMPA type of glutamate receptors. In the present study we investigated the regional distribution of SH- group modification by quantitative analysis of autoradiographic images of [3H]AMPA binding in tissue sections. We also compared the effect of SH- group modification to that of the chaotropic ion thiocyanate (SCN-) which has been generally utilized to study [3H]AMPA binding sites. Low levels of binding sites were observed in the absence of potassium thiocyanate (KSCN), with binding predominantly found in telencephalic structures. The presence of KSCN induced a relatively uniform and large (four- to fivefold) increase in binding throughout the different brain structures. Pretreatment of the tissue sections with the SH- group reagent p-chloromercuriphenylsulfonic acid produced a 0.5- to 1.5-fold increase in [3H]AMPA binding. The enhanced binding displayed a regional variation with the largest increase in binding observed in the outer layer of the parietal cortex whereas the lowest increase occurred in the striatum. These results indicate that SH- group modification of tissue sections produces an increase in [3H]AMPA binding similar to that observed in detergent-treated membrane preparations. Moreover they reveal that [3H]AMPA binding sites in different brain regions vary in their susceptibility to modification by SH- reagents, suggesting the existence in brain of a heterogeneous distribution of quisqualate/AMPA receptor subtypes.
Baudry
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Department of Psychobiology, University of California, Irvine 92717.
Monaghan
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Cotman
C
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Altar
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CA
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000818:Animals; D001345:Autoradiography; D001665:Binding Sites / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D007051:Ibotenic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D008297:Male; D010080:Oxazoles / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013382:Subtraction Technique; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D013861:Thiocyanates / Q000494:pharmacology; D014018:Tissue Distribution; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
D010080:Oxazoles; D013438:Sulfhydryl Compounds; D013861:Thiocyanates; D007051:Ibotenic Acid; D002731:4-Chloromercuribenzenesulfonate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C009941:potassium thiocyanate