Erowid References Database
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Fillion GMB.
“High-Affinity Binding of 3H 5-Hydroxytryptamine to Brain Synaptosomal Membranes; Comparison with 3H Lysergic Acid Diethylamide Binding”.
Molec. Pharmacol.. 1978;14(I):50-59.
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Abstract
The binding of 3H-serotonin (5-HT) and 3H-LSD to subcellular brain fractions was examined. Methods Cerebral tissues, usually striatum, from bovine brains, or in some assays horse brains, were homogenized and subcellular fractions and a purified synaptosomal membrane fraction were prepared. Binding assays were performed in Tris-HC1 buffer, pH 7.4, containing 100 mcM pargyline with the radioactive ligand in the presence and absence of the antagonist. Various drugs were examined for their effects on 3H-5-HT and 3H-LSD binding in the synaptosomal membrane fraction; IC50 values revere determined by log.probit analysis. 5-HT and LSD binding were also studied in crude brain preparations from rats after degeneration of the raphe-striatal serotoninergic system by stereotaxic injections, of 5,6-dibydroxytryptamine (10 mg/ml in isotonic NaC1 containing 0.02% ascorbic acid); 50 lug into the anterior ventricles and 70 mcg into the 3rd ventricle. Rats were killed after 12-14 days. Results 3H-5-HT binding involved 2 different sites corresponding to a high-affinity binding (KD=1-3 nM) and lower-affinity binding (KD=10.30 nM). Both types of binding involved sites representing saturable populations located on membranes; synaptosomal and microsomal membranes showed high binding capacity and mitochondria and synaptic vesicles showed low binding capacity. The purified synaptosomal fraction contained only high-affinity binding sites, low-affinity binding sites were present in nonsynaptosomal membrane fractions. Similarly LSD binding involved 2 sites (KD =3-4 nM and 20-30 nM) with only high affinity binding in synaptosomal membranes. The interaction of 5-HT and LSD showed that the high affinity binding sites for 5-HT and LSD were not identical. The ID 50 values for 5-HT, 5-hydroxy -N,N - dimethyltryptamine; N,N - dimethyltryptamine; 5-methoxytryptamine; tryptamine; 5-HLAA; LSD, methiothepin; cyproheptadine; cinanserin; 2-bromo-LSD; methysergide; dopamine; norepinephrine; octopamine; haloperidol; pimozide; pipamperone; chlorpromazine; chlorimipramine; dihydroergotamine; phenoxybenzamine and morphine are tabulated.
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