Inhibition by calmodulin antagonists of [3H]MK-801 binding in brain synaptic membranes.
In brain synaptic membranes not extensively washed, (+)-5-[3H]methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5, 10-imine ([3H]MK-801) binding was markedly inhibited in a concentration-dependent manner (at concentrations above 1 microM) by several compounds having antagonistic activity at the Ca(2+)-binding protein calmodulin. Scatchard analysis revealed that N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) inhibited the binding through a significant decrease in the density of binding sites without affecting the affinity at 10 microM. In membranes extensively washed and treated with a low concentration of Triton X-100, L-glutamic acid (Glu) drastically accelerated the initial association rate of [3H]MK-801 binding with glycine (Gly), almost doubling the initial association rate found in the presence of Glu alone. The addition of W-7 invariably reduced the initial association rate observed in the presence of either Glu alone or both Glu and Gly, without significantly altering the dissociation rate of bound [3H]-MK-801, irrespective of the presence of the two stimulatory amino acids. The maximal potencies of Glu, Gly, and spermidine in potentiating the binding were all attenuated by W-7. These results suggest that calmodulin antagonists may interfere with opening processes of an ion channel associated with an N-methyl-D-aspartate-sensitive subclass of excitatory amino acid receptors in rat brain.
Ogita
K
K
Department of Pharmacology, Setsunan University, Osaka, Japan.
Suzuki
T
T
Pingping
Z
Z
Yoneda
Y
Y
D000818:Animals; D001921:Brain / Q000378:metabolism*; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D016291:Dizocilpine Maleate / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D011919:Rats, Inbred Strains; D013268:Stimulation, Chemical; D013570:Synaptic Membranes / Q000378:metabolism*; D014316:Tritium
D002147:Calmodulin; D014316:Tritium; D016291:Dizocilpine Maleate