title: Actions of orexins on individual myenteric neurons of the guinea-pig ileum: orexin A or B?
abstract: The actions of orexins (orexin A and B, 10-300 nM) on individual myenteric neurons of the guinea-pig ileum in vitro were compared using intracellular recording methods. Both orexins caused membrane depolarizations associated with an increase in input neuronal resistance in S and AH neurons via a direct action. Orexin depolarizations reversed at about -90 mV, indicating they were due to an inactivation of K+ channels. Orexins facilitated fast excitatory postsynaptic potentials without affecting postsynaptic sensitivity to acetylcholine and adenosine 5'-triphosphate, indicating that the peptides may facilitate ganglionic transmission by increasing presynaptic release of neurotransmitters. Orexin B was sometimes more effective than orexin A and vice versa. It is concluded that orexin B increased neuronal activity via mechanisms similar to orexin A in the guinea-pig myenteric plexus.
authors.affiliation: Department of Autonomic Physiology, Medical Research Institute, Tokyo Medical and Dental University, Chiyoda-ku, Tokyo 101-0062, Japan. kataauto@tmd.ac.jp
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Katayama
authors.forename: Keiji
authors.initials: K
authors.lastname: Hirai
authors.forename: Tomoo
authors.initials: T
authors.lastname: Homma
authors.forename: Yumi
authors.initials: Y
authors.lastname: Noda
authors.forename: Kazuki
authors.initials: K
authors.lastname: Honda
mesh_terms: D000818:Animals; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects; D006168:Guinea Pigs; D007082:Ileum / Q000294:innervation*; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology*; D008297:Male; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology*; D009479:Neuropeptides / Q000494:pharmacology*; D018377:Neurotransmitter Agents / Q000494:pharmacology; D000068797:Orexins; D015221:Potassium Channels / Q000502:physiology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D000068797:Orexins; D015221:Potassium Channels