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Kadan MJ, Krohn AM, Evans MJ, Waltz RL, Hartig PR. 
“Characterization of 125I-Lysergic Acid Diethylamide Binding to Serotonin Receptors in Rat Frontal Cortex”. 
J.Neurochem.. 1984;43:601-606.
125I-Lysergic acid diethylamide (25I-LSD) is the first 125I-labeled ligand for serotonin receptor studies for this binding site. Regional distribution studies. Its binding to rat frontal cortex membranes is saturable, reversible, and stereospecific. Specific binding is linearly dependent on tissue concentration and represents 70-800f the total binding. Scatchard plots of the binding data are linear with a KD of 1.5 nM, a Bmax of 12.4 fmol/mg wet weight tissue, and a Hill slope of 1.02. The binding kinetics are highly temperature-dependent. At 37 degrees C the bimolecular association rate constant is 1.28 X 10^8 /min/M and the dissociation rate constant is 0.087 /min (t 1/2 = 8.0 min). At 0 degrees C < 4 0issociation occurs over 40 min and the association rate is similarly depressed. Inhibition of 125I-LSD binding by a vareity of serotonergic, dopaminergic, and adrenergic ligands reveals a 5-hydroxytryptamine2 (5-HT2) serotonergic profile for this binding site. Regional distribution studies of 125 I-LSD binding in rat brain show that areas with the highest levels of binding include the cortex and striatum. Iodinated radioligands can be synthesized with specific activities exceeding 2,000 Ci/mmol, which makes them approximately 75-fold more sensitive than tritiated radioligands. This high specific activity, coupled with the selectivity of 125I-LSD for 5-HT2 sites, makes this ligand a sensitive new probe for 5-HT2 serotonin receptors.
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