Taste responses to electrolytes in the frog glossopharyngeal nerve: enhancement by Ni2+ ions.
In studies of whole-nerve recordings from the frog glossopharyngeal nerve, Kashiwagura et al. reported that Ni2+ enhances responses to MgCl2 and NaCl and that such enhanced responses are suppressed by Ca2+. In the present study, it was found that the responses to electrolytes of single water fibers of the frog glossopharyngeal nerve are enhanced by Ni2+. Ni2+ enhances the responses to MgCl2, NaCl, and CaCl2. The enhancement of the response to CaCl2 suggests that inhibition of the enhanced response by Ca2+ is not caused by the relationship between Ca2+ and Ni2+ ions on the receptor membrane. Kitada reported that, in the absence of Ni2+, Ca2+ competitively inhibits the responses to Na+ and Mg2+; and Kitada and Shimada reported that the response to Ca2+ is competitively inhibited by Na+ and Mg2+. The possibility is discussed that inhibition of the enhanced response by Ca2+ is due to competition between Ca2+ and Na+ and between Ca2+ and Mg2+ for multiple specific receptor sites.
Kitada
Y
Y
Okayama University Dental School, Japan.
D000818:Animals; D001667:Binding, Competitive; D002118:Calcium; D004573:Electrolytes; D005930:Glossopharyngeal Nerve / Q000502:physiology*; D007477:Ions; D009532:Nickel; D011892:Rana catesbeiana; D011898:Ranidae; D012964:Sodium; D013649:Taste / Q000502:physiology*
D004573:Electrolytes; D007477:Ions; C022838:nickel chloride; D009532:Nickel; D012964:Sodium; D002118:Calcium