title: Possible nicotinic receptor-mediated modulation of synaptic transmission in nucleus of the solitary tract.
abstract: Signal transmission from afferent nerves to neurons in the nucleus of the solitary tract (NTS) may be mediated partially by nicotinic acetylcholine receptors (nAChRs). Here, we investigated nAChR-mediated signal transmission using rat NTS slices. First, we characterized nAChRs by obtaining patch-clamp recordings from NTS neuronal cell bodies. Under whole cell voltage-clamp conditions at -60 mV, application of nicotine induced an inward current, and this effect was blocked by hexamethonium. In outside-out patch recordings, nicotine was seen to induce a hexamethonium-sensitive single-channel current. Second, we investigated nAChR-mediated signal transmission. Fast synaptic transmission mediated by nAChRs was not detected. The action of diffusible acetylcholine (ACh) on nAChRs was then tested using the outside-out patches excised from NTS neurons as probes for ACh. When the patch was placed at a distance of 20-30 microm from the cell body, single-channel currents were recorded, and these were inhibited by hexamethonium. The frequency of channel opening was increased by high-extracellular potassium concentration solution suggesting the voltage-dependent release ofACh that acts on nAChRs. These results suggested that nAChR-mediated signal transmission from sensory afferents to NTS neurons is in part mediated by diffusible ACh.
authors.affiliation: Department of Neuroscience, Graduate School of Human and Environmental Studies, Kyoto University, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Shiraki
authors.forename: A
authors.initials: A
authors.lastname: Toyoda
authors.forename: H
authors.initials: H
authors.lastname: Sugino
authors.forename: A
authors.initials: A
authors.lastname: Hori
authors.forename: S
authors.initials: S
authors.lastname: Kobayashi
mesh_terms: D000109:Acetylcholine / Q000378:metabolism / Q000494:pharmacology*; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D018738:Hexamethonium / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009538:Nicotine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D010830:Physostigmine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011978:Receptors, Nicotinic / Q000502:physiology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D011978:Receptors, Nicotinic; D018738:Hexamethonium; D009538:Nicotine; D010830:Physostigmine; D000109:Acetylcholine; D011188:Potassium