Inhibition of MK801 binding in adult rat brain sections by conantokin-G and conantokin-T.
The functional interactions of conantokins with anatomical sites in rat brain have been assessed through displacement of the non-competitive N-methyl-D-aspartate receptor (NMDAR) antagonist, dizocilpine (MK801). The binding of (+)-3-[125I]-iodo-MK801 (1 nM) to coronal sections from adult rat brain was inhibited in a dose-dependent manner by conantokin-T (con-T) and conantokin-G (con-G). Quantitative densitometry was used to determine IC50 values for conantokin inhibition of [125I]-MK801 binding in the cortex, thalamus and hippocampus. Con-T completely inhibited [125I]-MK801 specific binding in all brain regions at a saturating concentration of 100 microM. Con-G was able to completely displace [125I]-MK801 in the cortex and thalamus, but only inhibited this same binding up to approximately 90% in the hippocampus. Both peptides maintained their inhibitory properties in the presence of 1 mM EDTA, suggesting that divalent cations are not required for their action in this regard. The added presence of spermine (150 microM) resulted in a two-fold increase in [125I]-MK801 binding and a two-fold decrease in the IC50 values for both peptides. The data obtained in this investigation further demonstrate that [125I]-MK801 is a useful probe for the indirect determination of functional NMDAR ligand binding sites in rat brain sections.
Klein
R C
RC
Department of Chemistry and Biochemistry and W.M. Keck Center for Transgene Research, University of Notre Dame, IN 46556, USA.
Castellino
F J
FJ
D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D020916:Conotoxins; D016291:Dizocilpine Maleate / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D018691:Excitatory Amino Acid Antagonists / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism*; D036341:Intercellular Signaling Peptides and Proteins; D008978:Mollusk Venoms / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D010456:Peptides, Cyclic / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*
D020916:Conotoxins; D018691:Excitatory Amino Acid Antagonists; D036341:Intercellular Signaling Peptides and Proteins; D008978:Mollusk Venoms; D010455:Peptides; D010456:Peptides, Cyclic; D016194:Receptors, N-Methyl-D-Aspartate; C063571:conantokin-T; D016291:Dizocilpine Maleate; C055407:conotoxin GV