title: Effects of injecting GABAergic agents into the medullary reticular formation upon swallowing induced by the superior laryngeal nerve stimulation in decerebrate cats.
abstract: The purpose of this study was to elucidate the role of the GABAergic system in the medullary reticular formation (MRF) in the control of swallowing. In acutely decerebrated cats (n = 12), swallowing was induced by electrical stimulation (0.3-6 V at 10-20 Hz for 10-20 s every minute) applied to the superior laryngeal nerve (SLN). The stimulus intensity was adjusted so that swallowing was induced two or four times during the period of the stimulation. Bicuculline, a GABA(A) receptor antagonist, was then injected (0.10-0.15 microl, 5 mM) into the MRF through a stereotaxically placed glass micropipette. In a total of 62 injections, 19 injections (30.6%) increased the frequency of SLN-induced swallowing when it was injected into the lateral part of the MRF corresponding to the nucleus reticularis parvocellularis (NRPv). In eight of the effective injections (42.1%) which increased the frequency of SLN-induced swallowing, SLN stimulation also induced coughing. With two injections, stimulation of the SLN-induced coughing but not facilitation of swallowing. On the other hand, an injection of 0.10-0.15 microl of 5 mM muscimol, a GABA(A) receptor agonist, into the NRPv decreased the frequency of SLN-induced swallowing. These results suggest that the NRPv neurons which are responsible for evoking swallowing are under the tonic inhibitory control of the GABAergic system.
authors.affiliation: Department of Physiology, Asahikawa Medical College, Midorigaoka-Higashi 2-1-1-1, Asahikawa 078-8510, Japan.
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Harada
authors.forename: Kaoru
authors.initials: K
authors.lastname: Takakusaki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kita
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Matsuda
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nonaka
authors.forename: Takashi
authors.initials: T
authors.lastname: Sakamoto
mesh_terms: D000818:Animals; D001640:Bicuculline / Q000008:administration & dosage; D001931:Brain Mapping; D002415:Cats; D003371:Cough / Q000503:physiopathology; D003655:Decerebrate State; D003679:Deglutition / Q000187:drug effects* / Q000502:physiology; D004558:Electric Stimulation; D004576:Electromyography; D018682:GABA Agents / Q000008:administration & dosage*; D005683:Gagging / Q000187:drug effects / Q000502:physiology; D007276:Injections, Intraventricular; D007823:Laryngeal Nerves / Q000502:physiology*; D007830:Larynx / Q000502:physiology; D008845:Microinjections; D009118:Muscimol / Q000008:administration & dosage; D010614:Pharynx / Q000294:innervation / Q000502:physiology; D012154:Reticular Formation / Q000187:drug effects* / Q000502:physiology
chemical_list: D018682:GABA Agents; D009118:Muscimol; D001640:Bicuculline