The open channel blocking drug, IEM-1460, reveals functionally distinct alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors in rat brain neurons.
The properties of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors were examined in various cell types isolated from young rat hippocampus, striatum and cerebellum using patch-clamp and fast application techniques. A dicationic adamantane derivative, IEM-1460, reversibly inhibited kainate-induced currents. In the presence of 100 microM IEM-1460, kainate currents in striatal giant cholinergic interneurons and hippocampal non-pyramidal neurons were inhibited by 95% and 81%, respectively, at Vh = - 70 mV. Striatal GABAergic principal cells, hippocampal pyramidal neurons and cerebellar Purkinje cells had low sensitivity to IEM-1460 (inhibition by 4-15%). Analysis of averaged data from the cell types studied revealed a highly significant positive correlation (r= 0.93, P < 0.01) between percentage inhibition by 100 microM IEM-1460 and relative calcium permeability of AMPA receptors, P(Ca)/P(Na). Also, within each brain structure, the sensitivity of IEM-1460 block was lower the stronger the outward rectification of kainate currents. Some hippocampal neurons exhibited intermediate sensitivity to IEM-1460. Kainate currents were suppressed by 40% in the presence of 100 microM IEM-1460. Meanwhile, AMPA receptors in this cell type had low calcium permeability (P(Ca)/P(Na) = 0.13) and demonstrated outwardly rectifying kainate currents. The interrelation of different properties of AMPA receptors considering their assembly is discussed. The data obtained suggest that IEM-1460 may be a convenient and promising marker of native AMPA receptor assembly: it selectively inhibits Ca(2+)-permeable, GluR2-lacking AMPA receptors.
Samoilova
M V
MV
Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St Petersburg. samoilov@VV3977.spb.su
Buldakova
S L
SL
Vorobjev
V S
VS
Sharonova
I N
IN
Magazanik
L G
LG
D000218:Adamantane / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001923:Brain Chemistry / Q000502:physiology; D002531:Cerebellum / Q000737:chemistry / Q000166:cytology; D003342:Corpus Striatum / Q000737:chemistry / Q000166:cytology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D006624:Hippocampus / Q000737:chemistry / Q000166:cytology; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000737:chemistry* / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors* / Q000502:physiology*
D018690:Excitatory Amino Acid Agonists; C110702:IEM 1460; D018091:Receptors, AMPA; D000218:Adamantane; D007608:Kainic Acid