FUNCTIONAL, ENDOGENOUSLY EXPRESSED 5-HYDROXYTRYPTAMINE 5-HT(7) RECEPTORS IN HUMAN VASCULAR SMOOTH-MUSCLE CELLS

Human uterine artery smooth muscle cells in culture were shown to expr ess constitutively both 5-ht(7)-receptor mRNA and 5-ht(7)-like recepto rs functionally linked to cyclic AMP formation. 5-Carboxamidotryptamin e (5-CT) and 5-HT enhanced forskolin-stimulated cyclic AMP accumulatio n in these cells, with pEC(50) values of 7.12 and 6.25, sumatriptan be ing very weakly active. Both methiothepin (0.1 mu M) and clozapine (1 mu M), but not the 5-HT4-receptor antagonist, SDZ 205-557 (10 mu M) an tagonized the effects of 5-CT. In reverse transcriptase-polymerase cha in reaction analysis, the mRNA for 5-ht(7), but not for 5-HT4 or 5-ht( 6) receptors was found to be strongly expressed in the same cells. The se findings represent a further step toward the recognition of 5-ht(7) receptors as real, functional receptors.