Thiocyanate stabilizes AMPA binding to the quisqualate receptor.
Calcium and chloride ions stimulated [3H]glutamate binding to quisqualate-sensitive [3H]glutamate binding sites 4-fold, as measured by quantitative autoradiography, whereas 100 mM potassium thiocyanate had no additional effect. In contrast, calcium and chloride had little effect on the binding of [3H](RS)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid ([3H]AMPA), but 100 mM thiocyanate stimulated binding 4-fold. AMPA displaced little [3H]glutamate binding from quisqualate-sensitive binding sites in the molecular layer of the cerebellum in the absence of thiocyanate. However, in the presence of thiocyanate AMPA became a more effective displacer, but still displaced only 44% of the quisqualate-sensitive [3H]glutamate binding. The distribution of [3H]glutamate binding to quisqualate-sensitive sites was similar to but not identical with that of [3H]AMPA binding. However, the distribution of AMPA-displaceable [3H]glutamate binding correlated highly (r = 0.97, P less than 0.0005) with that of [3H]AMPA binding. The results suggest that AMPA binds to a subclass of quisqualate-sensitive [3H]glutamate binding sites that are highly influenced by ionic environment and that quisqualate-sensitive binding sites exist in several states.
Nielsen
E O
EO
Department of Neurology, University of Michigan, Ann Arbor 48104-1687.
Cha
J H
JH
Honoré
T
T
Penney
J B
JB
Young
A B
AB
D000818:Animals; D001345:Autoradiography; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D004396:Coloring Agents / Q000494:pharmacology*; D005971:Glutamates; D007051:Ibotenic Acid / Q000031:analogs & derivatives / Q000378:metabolism*; D008024:Ligands; D008297:Male; D010069:Oxadiazoles; D010080:Oxazoles / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter / Q000032:analysis / Q000187:drug effects* / Q000378:metabolism; D013861:Thiocyanates / Q000494:pharmacology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid
D002712:Chlorides; D004396:Coloring Agents; D005971:Glutamates; D008024:Ligands; D010069:Oxadiazoles; D010080:Oxazoles; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D017981:Receptors, Neurotransmitter; D013861:Thiocyanates; D007051:Ibotenic Acid; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D002118:Calcium; C009941:potassium thiocyanate