Use of bioluminescent aequorin for the pharmacological characterization of5HT receptors

A convenient functional assay for 5HT2a and 5HT2c receptors is reported uti lizing the bioluminescent aequorin to detect intracellular calcium changes. Using this assay, the pharmacological properties of many 5HT ligands can b e determined in a 96-well format. The data indicate that the aequorin detec tion method is superior to the inositol phosphate assay with regard to spee d and scope. This system is also appropriate for kinetic studies of recepto r desensitization. We showed that the human 5HT2c receptor desensitizes in a biphasic manner, with a fast desensitization of approximately 90% of the total response occurring within 15 minutes while the remaining 10% response remains for at least 3 hours.