AJP - Regulatory, Integrative and Comparative Physiology, Vol 243, Issue 1 42-R48, Copyright © 1982 by American Physiological Society
High sensitivity of Xenopus gustatory receptors to amino acids and bitter substances
K. Yoshii, C. Yoshii, Y. Kobatake and K. Kurihara
The gustatory nerve responses of the aquatic toad Xenopus laevis to salts,
acids, amino acids, and bitter substances were recorded. 1) The gustatory
receptors were sensitive to amino acids and bitter substances. The
thresholds were 10(-7) M for Arg, 3 X 10(-9) M for strychnine, and 3 X
10(-8) M for quinine, 200-20,000 times lower than the thresholds for the
respective stimuli in the bullfrog. 2) The basic and the neutral amino
acids were effective whereas the acidic ones were not. Relations between
the responses and log stimulus concentrations for the basic amino acids
were linear in a wide concentration range whereas those for the neutral
ones were of S shape. Cross-adaptation did not occur among pairs of a basic
amino acid and a neutral one. 3) Responses to the basic amino acids and the
basic bitter substances were suppressed by the addition of salts to the
stimulating solutions, while those to the neutral and the acidic substances
were not suppressed.
