To investigate whether polymorphic forms of the human dopamine D4 receptor have different functional characteristics, we have stably expressed cDNAs of the D4 .2, D4 .4, and D4 .7 isoforms in several cell lines . Chinese hamster ovary CHO-K1 cell lines expressing D4 receptor variants displayed pharmacological profiles that were in close agreement with previous data from transiently expressed D4 receptors in COS-7 cells . Dopamine stimulation of the D4 receptors resulted in a concentration-dependent inhibition of the forskolin-stimulated cyclic AMP (cAMP) levels . The potency of dopamine to inhibit cAMP formation was about twofold reduced for D4 .7 (EC so of -37 nM) compared with the D4 .2 and D4 .4 variants (EC SO of -16 nM) . Antagonists block the dopamine-mediated inhibition of cAMP formation with a rank order of potency of emonapride > haloperidol = clozapine > raclopride . There was no obvious correlation between the efficacy of inhibition of forskolin-stimulated cAMP levels and the D4 subtypes . Dopamine could completely reverse prostaglandin E 2 -stimulated cAMP levels for all three D4 receptor variants . Deletion of the repeat sequence does not affect functional activity of the receptor . The data presented indicate that the polymorphic repeat sequence causes only small changes in the ability of the D4 receptor to block cAMP production in CHO cells . Key Words : Dopamine receptors-D4-Cyclic AMP-Variants .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.