5-HT is present in nerves of guinea pig sphincter of Oddi and depolarizes sphincter of Oddi neurons.
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.
Hillsley
K
K
Department of Anatomy and Neurobiology, University of Vermont, Burlington, Vermont 05405, USA.
Mawe
G M
GM
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
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