Original ArticlesHuman genetic variations in the 5HT2A receptor a single nucleotide polymorphism identified with altered response to clozapineHarvey, Laynea; Reid, Ronald Eb; Ma, Caixiab; Knight, Peter JKa; Pfeifer, Tom Aa; Grigliatti, Thomas AaAuthor Information aDepartment of Zoology, Faculty of Science, and bDivision of Biomolecular and Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3. This research was funded by grants from the National Science and Engineering Council of Canada and the David Collins Dawson Endowment Fund to the Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, Canada. Correspondence to Ronald E. Reid, Division of Biomolecular and Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3. E-mail: [email protected] Received 9 October 2002 Accepted 21 November 2002 Pharmacogenetics: February 2003 - Volume 13 - Issue 2 - p 107-118 Buy Abstract Objective to determine if the agonist serotonin and antagonists loxapine and clozapine have an altered potency for four allelic variants (T25N, I197V, A447V, and H452Y) of the human 5HT2A receptor when compared to the wild-type allele. Methods The receptor or its variants are studied in an in-vitro functional assay system consisting of a Sf9 insect cell line that is stably transformed with the human wild-type and mutant alleles. This assay system measures release of calcium stores due to receptor activation by agonists and inhibition of this agonist stimulated response by antagonists. Results Both loxapine and clozapine exhibit non-competitive antagonism of serotonin stimulation of the human 5HT2A receptor signal transduction system and loxapine is the more potent inhibitor. This study shows that the I197V allele requires a two-fold higher concentration of the atypical neuroleptic clozapine to inhibit serotonin stimulation compared to the wild-type receptor (P = 0.036). The I197V mutation does not affect the inhibition of serotonin stimulation by the typical neuroleptic loxapine nor does it alter the activation of the receptor by serotonin. It is also significant that the results of this study indicate that the T25N, A447V, and H452Y mutations in the human 5HT2A receptor do not significantly alter the response of the receptor to the agonist serotonin or the antagonists loxapine and clozapine. © 2003 Lippincott Williams & Wilkins, Inc.