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Maayani S, Weinstein H, Green JP. 
“Brain 5-RT And LSD Binding Sites”. 
Fed. Proc.. 1979;38(3):376.
[3H]-LSD binding sites were characterized in the P-2 membrane fractions of guinea pig cortex by using a "cross binding" technique with 5-HT at 10-5 M to define the non-specific binding. [3H]-5-HT binding sites were studied in the same preparation using 10-5 M LSD to define the non-specific binding. Both the LSD and the 5-HT binding sites were found to be homogeneous, non-interacting populations, with dissociation constants of 5.7 +/- 1.4x 10-9 M (5-PT sites) and 6.2 +/- 0.2x 10-9 M (LSD sites) Bmax values were 95 +/- 6 and 190 +/-13 fmoles/mg protein, respectively. The dissociation constants of various competitive ligands, determined by competition-displacement experiments, had the following values (nM): For 3H -LSD sites (10- M 5-HT) - D-7.5D (10) BOL (15), Cyproheptadine (100), 5-HT (100), Tryptamine (;000), 6-HT (1700), 7-HT (3000). For 3H -5-HT sites (10-5 M D-LSD) - 5-HT (4), D-LSD (34), BOL (80), Tryptamine (100), Cyproheptadine (840) 6-HT (2000), 7-HT (4000). Although with these "cross binding' techniques [3H]-5-HT or [3H]-LSD should label the same population of binding sites, the measured Bmax and Kd valises of the cold ligands differ markedly. One possible interpretation is that although the receptor pools [or the two ligands coincide, different molecular changes are induced in the binding sites by each of them. This hypothesis is tested by experiments on the kinetics of labeled and cold 1igand bluding.
Notes # : Abstr. No. 782
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