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

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 microM) and clozapine (1 microM), but not the 5-HT4-receptor antagonist, SDZ 205-557 (10 microM) 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.