Functional, endogenously expressed 5‐hydroxytryptamine 5‐ht7 receptors in human vascular smooth muscle cells

Abstract

Human uterine artery smooth muscle cells in culture were shown to express constitutively both 5‐ht₇ receptor mRNA and 5‐ht₇‐like receptors functionally linked to cyclic AMP formation. 5‐Carboxamidotryptamine (5‐CT) and 5‐HT enhanced forskolin‐stimulated cyclic AMP accumulation in these cells, with pEC₅₀ values of 7.12 and 6.25, sumatriptan being very weakly active. Both methiothepin (0.1 μm) and clozapine (1 μm), but not the 5‐HT₄‐receptor antagonist, SDZ 205–557 (10 μm) antagonized the effects of 5‐CT. In reverse transcriptase‐polymerase chain reaction analysis, the mRNA for 5‐ht₇, but not for 5‐HT₄ or 5‐ht₆ receptors was found to be strongly expressed in the same cells. These findings represent a further step toward the recognition of 5‐ht₇ receptors as real, functional receptors.