Intracellular spermine confers rectification on rat calcium-permeable AMPA and kainate receptors.
1. Whole-cell recordings were made from cerebellar granule cells cultured in high-K+ medium to induce expression of Ca(2+)-permeable AMPA receptors. Current-voltage (I-V) plots of agonist-evoked responses showed varying degrees of inward rectification, but became linear within 5-10 min. 2. Recombinant Ca(2+)-permeable kainate receptors, composed of GluR6(Q)/KA-2 subunits, exhibited rectifying whole-cell I-V plots that became linear in outside-out patches. 3. Loss of rectification in granule cells was prevented by including 100 microM spermine in the pipette; the degree of rectification was then correlated with Ca2+ permeability. 4. Spermine also prevented loss of rectification in patches containing GluR6(Q)/KA-2 receptors (IC50, 1.7 microM). 5. We suggest that spermine, or a similar cellular constituent, may act as a cytoplasmic factor conferring inward rectification on Ca(2+)-permeable non-NMDA receptors, and that 'washout' of this factor underlies the observed loss of rectification.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D010539:Permeability; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000187:drug effects / Q000378:metabolism*; D018092:Kainic Acid Receptors / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins; D013096:Spermine / Q000502:physiology*
D002118:Calcium; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D011994:Recombinant Proteins; D013096:Spermine