title: 5-HT is present in nerves of guinea pig sphincter of Oddi and depolarizes sphincter of Oddi neurons.
abstract: This study involved immunohistochemistry and intracellular electrophysiology to investigate serotonergic neurotransmission in the sphincter of Oddi (SO). 5-Hydroxytryptamine (HT)-positive neurons (14 cells/preparation) and nerve fibers were observed in the ganglionated plexus. Serotonergic nerve fibers, which persisted under 2- to 6-day organ culture, were densely distributed, with varicose endings encircling some SO neurons. When 5-HT was applied to SO neurons, it elicited three different responses: 1) a fast depolarization to 5-HT in 31 of 62 cells was mimicked by 2-methyl-5-HT and blocked by LY-278584 (1 microM); 2) a prolonged depolarization to 5-HT in 21 of 62 cells evoked an increase in input resistance and was attenuated by the 5-HT1P antagonist renzapride (1 microM) but not by the 5-HT4 antagonist SDZ-205557 (0.1-10 microM); and 3) an indirect depolarization blocked by TTX or atropine was observed in 32 of 62 cells. 5-HT superfusion elicited a dose-dependent monophasic depolarization (EC50 = 2 microM, n=14). In conclusion, 5-HT is present in nerves of the SO and elicits both 5-HT3 and 5-HT1P receptor-mediated depolarizations, supporting the concept that 5-HT plays a role in SO regulation.
authors.affiliation: Department of Anatomy and Neurobiology, University of Vermont, Burlington, Vermont 05405, USA.
authors.forename: K
authors.initials: K
authors.lastname: Hillsley
authors.forename: G M
authors.initials: GM
authors.lastname: Mawe
mesh_terms: D010129:4-Aminobenzoic Acid / Q000494:pharmacology; D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001549:Benzamides / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D005071:Evoked Potentials / Q000187:drug effects / Q000502:physiology; D005725:Ganglia, Autonomic / Q000502:physiology; D006168:Guinea Pigs; D007150:Immunohistochemistry; D007191:Indazoles / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009197:Myenteric Plexus / Q000502:physiology*; D009412:Nerve Fibers / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D009924:Organ Culture Techniques; D012701:Serotonin / Q000494:pharmacology* / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology*; D009803:Sphincter of Oddi / Q000294:innervation*; D013779:Tetrodotoxin / Q000494:pharmacology; D014326:Tropanes / Q000494:pharmacology; D062366:para-Aminobenzoates
chemical_list: D001549:Benzamides; D019086:Bridged Bicyclo Compounds, Heterocyclic; D007191:Indazoles; D012702:Serotonin Antagonists; D014326:Tropanes; D062366:para-Aminobenzoates; C061531:LY 278584; C072790:2-methoxy-4-amino-5-chlorobenzoic acid 2-(diethylamino)ethyl ester; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D013779:Tetrodotoxin; D001285:Atropine; C053006:renzapride; D010129:4-Aminobenzoic Acid