TEMPERATURE CHANGE ON THE RESPONSE OF TASTE RECEPTORS 161 



Therefore, not only the temperature but also the concentration of taste 

 solutions were changed as a next step. One example of an experiment on 

 the NaCl-sensitive unit is shown in Fig. 11. Numbers of impulses dis- 

 charged is increased by raising or lowering the temperature of Ringer's 

 solution. When NaCl concentration is low, the curve relating the impulse 

 frequency to the temperature is similar to that obtained with Ringer's 

 solution, showing the minimal response at 30 C. However, by increasing 



Large spikes 

 O — 1/256M 

 '■' quinine 



Small spikes 



K 1/256 M 



quinine 



b Ringer 



10 20 30 



Temperature ( ' C ) 



Fig. 10. Impulse frequency-temperature relationships of large and small units, 



obtained from the same experiment. Ordinate ; number of impulses in the 



first second, abscissa ; temperature of solutions. From Nagaki, Sato and 



Yamashita, unpublished. 



the concentration, the response to the solution of 30'C becomes increased 

 prominently, and with 1 m NaCl the response shows the maximum at 30'C. 

 This is more clearly shown in the righthand figure of Fig. 11. It is seen 

 that increase in the impulse frequency with an increase in the concentration 

 is greatest at 30 C, and it becomes reduced with a rise or fall of the tem- 

 perature. Response of a quinine-sensitive unit to quinine solutions of 

 varying temperatures and of varying concentrations is shown in Fig. 12. 

 It shows similar findings to those presented in Fig. 11. All the experi- 

 ments on single taste units, in which both concentration and temperature 

 of solutions were changed, yielded similar results to those in Figs. 11 and 

 12. Results obtained with single taste units are essentially the same as 

 those obtained with the whole chorda tympani, and indicate that sensitivity 

 to taste stimuli is greatest when the temperature of solutions is 30^C or at 

 the temperature of the tongue. 



