TEMPERATURE CHANGE ON THE RESPONSE OF TASTE RECEPTORS 159 



specific, but the unit responding to HCi is also sensitive to other kinds of 

 stimuH and to cooHng rather than warming. The unit sensitive to water is 

 greater in spike height than the unit sensitive to NaCl. Difference in pro- 

 perties in large and small fibres is shown in Table 3. The large fibre did 

 not respond to NaCl, while the small fibre did not show response to water. 

 The latter also responded to saccharine, but not the former. 



Table 3. Difference in response between 

 large and small fibres, as measured by the 

 impulse number in the first 1 sec after 

 STIMULI (30°C) (from Nagaki, Sato and Yama- 



SHITA, UNPUBLISHED). 



Response of a cold-taste unit to water and Ringer's solution of varying 

 temperatures is shown in Fig. 8. The unit responded intensely to water 

 and to Ringer's solution of low temperature. The impulse frequency 

 reaches maximum within 1-2 sec after application of the solution and de- 

 clines thereafter. In general rate of decline in the impulse frequency be- 

 comes prolonged with a fall in temperature. This is more clearly shown in 

 Fig. 9, in which impulse number in 1 sec is plotted against time. There- 

 fore numbers of impulses in the first 1 sec after stimulation was measured 

 and was taken as a measure for representing the response magnitude. 



RESPONSE OF WARM- OR COLD-TASTE UNITS TO 

 SOLUTIONS OF VARYING TEMPERATURES 



Responses obtained from a single unit to 1/2 m NaCl, 1/256 m quinine or 

 1 256 M HCI of varying temperatures were rather variable. Some units 

 showed maximal response at 30 C, as shown in Fig. 7, while in other units 

 response was not maximal at 30 C, as shown in Fig. 10. In this figure res- 

 ponses of two units to 1 256 m quinine are shown. The unit of large spike 

 height shows decreasing frequency with a rise in temperature, while the 

 unit of small spike shows the maximal frequency at 30'C. This variable 

 response of units to solutions of varying temperature may be attributed to 

 (i) variable sensitivity of units to taste stimuli and (ii) the fact that any units 

 respond to both taste and thermal stimuli. 



