title: 5-HT(7)-like receptors mediate serotonergic modulation of photo-responsiveness of the medulla bilateral neurons in the cricket, Gryllus bimaculatus.
abstract: Serotonin (5-HT) suppresses the photo-responsiveness of medulla bilateral neurons (MBNs) that are involved in the coupling mechanism of the bilaterally paired optic lobe circadian pacemakers in the cricket, Gryllus bimaculatus. We found that forskolin, a highly specific activator of adenylate cyclase, mimicked the effects of serotonin on the MBNs. This fact suggests the involvement of cyclic 3', 5'-adenosine monophosphate (cAMP) in mediating the action of serotonin. We therefore tested the effects of various 5-HT receptor agonists and antagonists that are coupled to adenylate cyclase to specify the receptor involved. Application of 8-OH-DPAT that has affinity for both 5-HT(1A) and 5-HT(7) receptors suppressed the photo-responsiveness, like forskolin. The inhibitory effect of 8-OH-DPAT was effectively blocked by clozapine, a high affinity 5-HT(7) receptor antagonists with a very low affinity for 5-HT(2). Ketanserin, a selective 5-HT(2) antagonist, and NAN-190, a 5-HT(1A) antagonist, did not block it. These results suggest that serotonergic suppression of the photo-responsiveness of the MBNs is mediated by 5-HT(7)-like receptor subtypes.
authors.affiliation: Department of Physics, Biology and Informatics, Faculty of Science and Research Institute for Time Studies, Yamaguchi University, Yamaguchi, Japan.
authors.forename: A S M
authors.initials: AS
authors.lastname: Saifullah
authors.forename: Kenji
authors.initials: K
authors.lastname: Tomioka
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D003024:Clozapine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006135:Gryllidae / Q000502:physiology* / Q000528:radiation effects*; D007650:Ketanserin / Q000494:pharmacology; D008027:Light; D009474:Neurons / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects*; D010879:Piperazines / Q000494:pharmacology; D011985:Receptors, Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D014795:Visual Pathways / Q000187:drug effects
chemical_list: D010879:Piperazines; D011985:Receptors, Serotonin; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C104425:serotonin 7 receptor; C058895:1-(2-methoxyphenyl)-4-(4-(2-phthalimido)butyl)piperazine; D005576:Colforsin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D007650:Ketanserin; D003024:Clozapine