Effects of inorganic constituents of saliva on taste responses of the rat chorda tympani nerve.
The effects of saliva on the taste responses of the chorda tympani nerve to the 4 standard chemical stimuli (sucrose, NaCl, HCl, and quinine hydrochloride) and water were investigated in anesthetized rats. When the tongue was adapted to pilocarpine-stimulated whole saliva (pH 8.7), the magnitude of neural response to sucrose was about 2 times that obtained when the tongue was adapted to distilled water. Under saliva-adapted conditions, the magnitude of responses to other taste stimuli was reduced by 10-30%, and the water response appeared. These changes were dependent on the concentration of electrolytes (Na+, K+, Cl-, and HCO3-) and on the pH of the saliva. When the tongue was adapted to 10-30 mM NaHCO3 (pH 8.4-8.6), taste and water responses were similar to those under saliva-adapted conditions. Single fiber analyses revealed that the enhancement of the sucrose response after adaptation to NaHCO3 was produced by an increased overall activity of sucrose-responsive fibers. The correlation coefficients of the magnitude of the taste responses between the 4 taste stimuli remained unchanged, but the water response showed a high correlation to HCl and quinine hydrochloride responses after adaptation. Possible mechanisms for the effects of saliva on taste and water responses were discussed.
Matsuo
R
R
Department of Oral Physiology, Faculty of Dentistry, Osaka University, Japan.
Yamamoto
T
T
D000818:Animals; D002814:Chorda Tympani Nerve / Q000502:physiology*; D004573:Electrolytes / Q000378:metabolism*; D006851:Hydrochloric Acid / Q000494:pharmacology; D008297:Male; D009412:Nerve Fibers / Q000187:drug effects / Q000502:physiology; D010862:Pilocarpine / Q000494:pharmacology; D011803:Quinine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012463:Saliva / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology; D013649:Taste / Q000502:physiology*
D004573:Electrolytes; D010862:Pilocarpine; D012965:Sodium Chloride; D013395:Sucrose; D011803:Quinine; D006851:Hydrochloric Acid