332 



HARRY GRUNDFEST 



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mV 

 20- 



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Fig. 5. Electrical activity in single taste buds produced by four standardized 

 stimuli: (1) salt, (2) sweet, (3) bitter and (4) acid. (Below) — Records of potentials 

 evoked by the four substances acting on a single taste bud. (Above) — Different 

 patterns of responses in 1 1 different cells. (Unpublished data, courtesy of Beidler 



and Kimura.) 



cells is probably chemical. The intermediate cells generate only graded, sus- 

 tained hyperpolarizing potentials (Fig. 6), or both hyperpolarizing and de- 

 polarizing activity depending on the cell and the wavelength of the stimulating 

 light (Fig. 7). Hyperpolarization certainly cannot produce ephaptic excitation 

 of ganglion neurons, yet the hyperpolarization clearly causes depolarizing 

 generator potentials and spikes in the neuron (Fig. 6). 



At the time Svaetichin first described the hyperpolarizing potentials, 

 Granit (cf. 1955) stated the then generally held opinion: ". . . it is . . . impos- 

 sible to accept the idea that hyperpolarization causes a discharge" because of 

 the "unequivocal . . . correlation between excitation and depolarization, and 

 between hyperpolarization and inhibition" (p. 32). When Svaetichin (1956) 

 reported his data in full he noted that hyperpolarization which causes activity 



