title: Drug antagonism and reversibility of the binding of indoleamines in brain.
abstract: The specificity of the binding of serotonin to brain preparations was investigated with various competitive agents. A probable relationship between their structure and their capability of displacement was suggested. Bufotenine and morphine displaced serotonin (0.5 X 10(-5) M) binding to synaptic membranes 87 and 49% respectively. Dissociation constants of the binding of 5-HT and tryptamine to synaptic membranes, and displacement constants of certain drugs were determined. The binding of 5-HT and tryptamine to calf brain preparations was also investigated by equilibrium dialysis, in order to determine affinity constants and reversibility of the binding. Differences were noted in the specificity of binding sites for serotonin and tryptamine, suggesting a different binding site for tryptamine. Extrapolations of Scatchard plots were used for determination of the constants. A characteristic low dissociation constant was found for 5-HT in synaptic membranes (K approximately X 10(-6) M). Probably, the binding macromolecule (receptor?) is a proteolipid.
mesh_terms: D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism*; D002027:Bufotenin / Q000378:metabolism / Q000494:pharmacology; D002417:Cattle; D006213:Hallucinogens; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D051379:Mice; D009020:Morphine / Q000378:metabolism / Q000494:pharmacology; D004130:N,N-Dimethyltryptamine / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013570:Synaptic Membranes / Q000187:drug effects; D013788:Thalamus / Q000187:drug effects; D014363:Tryptamines / Q000378:metabolism*
chemical_list: D006213:Hallucinogens; D014363:Tryptamines; D002027:Bufotenin; D012701:Serotonin; D009020:Morphine; D004130:N,N-Dimethyltryptamine