AJP - Regulatory, Integrative and Comparative Physiology, Vol 264, Issue 6 1071-R1076, Copyright © 1993 by American Physiological Society
Large enhancement of canine taste responses to amino acids by salts
T. Ugawa and K. Kurihara
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
The effects of salts on the canine taste responses to amino acids were
examined by recording the activity of the chorda tympani nerve. 1) The
tonic responses to most amino acids examined were significantly enhanced by
the presence of various salts. 2) The degree of the enhancement varied with
the species of amino acid and salt. The responses to most amino acids were
enhanced by sodium, potassium, and calcium salts, but not enhanced by
magnesium salts. The response to methionine, for example, was enhanced by
NaCl, but not by Na phosphate of equimolar Na+. 3) The responses to glycine
and alanine were suppressed by high concentrations of NaCl. 4) The presence
of salts (NaCl and CaCl2) enhanced the responses to amino acids without
affecting the thresholds for the amino acids, suggesting that the presence
of the salts did not change the affinity of amino acids to the receptor
sites. 5) The enhancing effects of salts on the responses to amino acids
could not be explained in terms of permeability of cation and anion of
salts. It was speculated that the binding of cation and anion of salts on
the receptor membranes induces exposure of the receptor sites for amino
acids available for binding of amino acids.
