High-affinity kainate binding sites in living slices of rat neocortex: characterization and regulation.
We have characterized a high-affinity kainate binding site in in vitro living rat neocortical slices using [3H]kainate. [3H]Kainate labelled at least two binding sites, the higher affinity site with a Kd of 7.1 nM and a Bmax of 71.2 fmol/mg protein. This high-affinity binding site showed a pharmacology consistent with a kainate receptor with competition by kainate and domoic acid, as well as the (RS)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate antagonist 6-cyano-2,3-dihydroxy-7-nitroquinoxaline. Increases in cellular depolarization induced by 2-h preincubations in veratridine and glutamate led to a significant 55% average decrease in [3H]kainate binding in adult cortex. Similarly, preincubation in kainate led to a significant average 26% decrease in binding. In both instances, Eadie-Hofstee analysis of saturation binding data revealed that the decreased binding reflected changes in receptor number. At different postnatal ages, increases in cellular depolarization significantly decreased binding (< 20 days postnatal age, -86%; > 60 days, -48%). Kainate treatment also significantly decreased binding at all ages (-64% at < 20 days; > 60 days, -18%), with significant differences noted between ages. These age-dependent effects are unlike those previously described for either N-methyl-D-aspartate [Lanius and Shaw (1992) Anat. Rec. 232, 54(A)] or (RS)-alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate high affinity receptors [Shaw and Lanius (1992) Devl Brain Res. 68, 225-233].(ABSTRACT TRUNCATED AT 250 WORDS)
Lanius
R A
RA
Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
Shaw
C
C
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000367:Age Factors; D000818:Animals; D001667:Binding, Competitive; D002540:Cerebral Cortex / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D007608:Kainic Acid / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley / Q000254:growth & development; D017470:Receptors, Glutamate / Q000145:classification / Q000187:drug effects / Q000378:metabolism*; D018092:Kainic Acid Receptors; D014701:Veratridine / Q000494:pharmacology
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D005971:Glutamates; D018698:Glutamic Acid; D007608:Kainic Acid; D016202:N-Methylaspartate; D009419:Nerve Tissue Proteins; D011810:Quinoxalines; D017470:Receptors, Glutamate; D018092:Kainic Acid Receptors; D014701:Veratridine; C012301:domoic acid