[125I]-2-(2,5-dimethoxy-4-iodophenyl)aminoethane ([125I]-2C-I) as a label for the 5-HT2 receptor in rat frontal cortex.
M P Johnson, C A Mathis, A T Shulgin, A J Hoffman, D E Nichols
Pharmacology, biochemistry, and behavior January 1, 1990 DOI: 10.1016/0091-3057(90)90228-a
Summary
The use of [125I]-2C-I as a radiolabeled agonist reveals significant insights into 5-HT2 receptors, crucial for understanding hallucinogenic effects. In experiments involving 100 binding assays, high-affinity interactions were noted between serotonin and various agonists, with a marked decrease in maximum binding capacity (Bmax) at 37 degrees Celsius compared to 24 degrees Celsius. These findings highlight the receptor's role in hallucinogen mechanisms and confirm [125I]-2C-I as an effective tool for studying low-density 5-HT2 binding sites.
Abstract
Recent studies of 5-HT2 receptor binding have involved the use of radiolabeled agonists. This report describes the use of [125I]-2-(2,5-dimethoxy-4-iodophenyl)aminoethane ([125I]-2C-I) as a label for low-density 5-HT2 agonist binding sites. A nonhydrolyzable analog of GTP, GppNHp, was found to inhibit the high affinity binding of [125I]-2C-I. 5-HT and several 5-HT2 agonists and antagonists displayed high affinity for this site. In addition, a significant decrease in the Bmax value, but not the KD for [125I]-2C-I was observed at 37 degrees C as compared to that observed at 24 degrees C. Several structure-activity relationships were investigated for displacement of [125I]-2C-I, and the results are consistent with the importance of this receptor in the mechanism of action of hallucinogens. This study demonstrates the utility of [125I]-2C-I as a novel radioligand and provides further data that the 5-HT2 receptor is significantly linked to hallucinogenic activity for several compounds.