title: Neuronal responses of the nucleus tractus solitarius to oral stimulation with umami substances.
abstract: In order to investigate coding mechanisms of special taste modality (umami), responses of neurons within the nucleus tractus solitarius (NTS) to oral stimulation with monosodium glutamate, disodium 5'-inosinate (IMP) or their mixture were recorded in the conventional electrophysiological method. Results obtained were as follows: Neither MSG-best nor IMP-best neuron was recorded within the NTS as in the primary taste afferents. Some of the sucrose-best neurons, NaCl-best neurons and HCl-best neurons responded to oral stimulation with MSG or IMP. A remarkable synergistic effect was observed in all of the sucrose-best neurons and in some of the NaCl-best neurons but not in all of the HCl-best neurons, when the mixed solution of MSG and IMP was applied into the oral cavity. As to the sucrose-best neurons, potency of the synergism was positively correlated with the responsiveness to sucrose. No correlation was recognized between them in the case of NaCl-best neurons. These results suggest a view that the sucrose-best neurons and the NaCl-best neurons which show the synergism may participate in coding umami taste.
authors.affiliation: Department of Physiology, Okayama University Dental School, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Adachi
authors.forename: M
authors.initials: M
authors.lastname: Aoyama
mesh_terms: D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D007291:Inosine Monophosphate / Q000502:physiology; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D009474:Neurons / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D012970:Sodium Glutamate; D013649:Taste / Q000502:physiology*; D013650:Taste Buds / Q000502:physiology*; D013652:Taste Threshold / Q000502:physiology
chemical_list: D007291:Inosine Monophosphate; D012970:Sodium Glutamate