Usefulness of HeLa cells to evaluate inverse agonistic activity of antihistamines

► Pretreatment with inverse agonists suppressed H1R gene expression to below its basal level. ► Basal H1R mRNA expression was unchanged by the pretreatment with neutral antagonists. ► Both inverse agonists and neutral antagonists suppressed histamine-induced H1R mRNA elevation. ► HeLa cells are more convenient and useful than the existing methods to evaluate the inverse agonistic activity of antihistamines.