DYNAMICS OF TASTE CELLS 



139 



subsequent magnitude of response to suprathreshold chemical stimuli. 

 Continuous adaptation to distilled water can, however, lower the salt 

 threshold for human subjects (Pfaffmann and McBurney, 1962). 



RESPONSE OF TASTE CELLS, 

 NERVE FIBERS AND NERVE BUNDLES 



Single Taste Cells 



The magnitude of electrical depolarization of the taste cell, as measured 

 with the aid of a KCl micropipette, is taken as an index of the response 

 of the taste cell to applied chemical stimuli. The resulting stimulus- 

 response curves can be satisfactorily described by the fundamental taste 

 equation. Each taste cell, however, differs in overall sensitivity as well as 

 its relative magnitude of response to a series of select stimuh such as 

 various concentrations of NaCl, sucrose, HCl and quinine HCl (see 

 Table 3). Many taste cells do not respond to sucrose, but others do. 

 Some respond to sucrose as well as to salt and acid. Thus, highly specific 

 taste receptors that respond to but one type of stimulus are not found 

 (Kimura and Beidler, 1961). 



Table 3. 



Response in Millivolts of the Hamster Taste Receptor to Basic Stimuli 

 OF Four Taste Qualities 



From Kimura and Beidler, 1961. 



Single Chorda Tympani Taste Fibers 



Since a single nerve fiber may innervate several taste cells, how specific 

 are the single fibers ? The average frequency of nerve impulses per unit 

 time is taken as an index of the magnitude of response of the unit (all the 

 cells innervated by the single taste fiber) to applied chemical stimuli. The 

 researches in the laboratories of Zotterman (Cohen, Hagiwara and 

 Zotterman, 1955 ; Zotterman, 1955), Pfaff'mann (Pfaff'mann, 1941 ; 1955) 

 Sato (Sato and Kusano, 1960) and the author's (1957) have all shown 



