125I-LSD: a high sensitivity ligand for serotonin receptors

125I-labeled receptor ligands offer unique advantages over their 3H-labeled counterparts. Carrier-free 125I-labeled ligands can be synthesized with specific activities of up to 2170 Ci/mmol while (mono) tritium labeled ligands are limited to 29 Ci/mmol. Therefore, 125I-labeled ligands can be approximately 70-fold more sensitive than 3H-labeled ligands in detecting receptor sites. In addition, 125I-labeled ligands emit relatively energetic X-rays and γ-rays which are readily detected by gamma counting equipment. The authors report here the serotonergic binding properties of 125I-LSD the first reported 125I-labeled ligand for serotonin receptors. (Auth.)