title: Molecular and pharmacological characterization of serotonin 5-HT2α and 5-HT7 receptors in the salivary glands of the blowfly Calliphora vicina.
abstract: Secretion in blowfly (Calliphora vicina) salivary glands is stimulated by the biogenic amine serotonin (5-hydroxytryptamine, 5-HT), which activates both inositol 1,4,5-trisphosphate (InsP(3))/Ca(2+) and cyclic adenosine 3',5'-monophosphate (cAMP) signalling pathways in the secretory cells. In order to characterize the signal-inducing 5-HT receptors, we cloned two cDNAs (Cv5-ht2α, Cv5-ht7) that share high similarity with mammalian 5-HT(2) and 5-HT(7) receptor genes, respectively. RT-PCR demonstrated that both receptors are expressed in the salivary glands and brain. Stimulation of Cv5-ht2α-transfected mammalian cells with 5-HT elevates cytosolic [Ca(2+)] in a dose-dependent manner (EC(50) = 24 nM). In Cv5-ht7-transfected cells, 5-HT produces a dose-dependent increase in [cAMP](i) (EC(50) = 4 nM). We studied the pharmacological profile for both receptors. Substances that appear to act as specific ligands of either Cv5-HT(2α) or Cv5-HT(7) in the heterologous expression system were also tested in intact blowfly salivary gland preparations. We observed that 5-methoxytryptamine (100 nM) activates only the Cv5-HT(2α) receptor, 5-carboxamidotryptamine (300 nM) activates only the Cv5-HT(7) receptor, and clozapine (1 µM) antagonizes the effects of 5-HT via Cv5-HT(7) in blowfly salivary glands, providing means for the selective activation of each of the two 5-HT receptor subtypes. This study represents the first comprehensive molecular and pharmacological characterization of two 5-HT receptors in the blowfly and permits the analysis of the physiological role of these receptors, even when co-expressed in cells, and of the modes of interaction between the Ca(2+)- and cAMP-signalling cascades.
authors.affiliation: Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Röser
authors.forename: Nadine
authors.initials: N
authors.lastname: Jordan
authors.forename: Sabine
authors.initials: S
authors.lastname: Balfanz
authors.forename: Arnd
authors.initials: A
authors.lastname: Baumann
authors.forename: Bernd
authors.initials: B
authors.lastname: Walz
authors.forename: Otto
authors.initials: O
authors.lastname: Baumann
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Blenau
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D004175:Diptera / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D044402:Receptor, Serotonin, 5-HT2A / Q000235:genetics / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000235:genetics / Q000378:metabolism*; D012469:Salivary Glands / Q000378:metabolism*; D020539:Sequence Analysis, Protein; D012701:Serotonin / Q000494:pharmacology
chemical_list: D019476:Insect Proteins; D044402:Receptor, Serotonin, 5-HT2A; D011985:Receptors, Serotonin; D012701:Serotonin