136 LLOYD M. BEIDLER 



the taste nerve regenerates and reinnervates the papillae, the taste buds 

 reform. Similar experiments have already been undertaken by Sandmeyer 

 (Sandmeyer, 1895); and Boeke (1917) and Guth (1958) substituted a non- 

 taste sensory nerve, and taste buds also reformed. How the sensory nerve 

 acts to modulate the taste-cell-forming epithelial cells is not known. 





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Fig. 1. Autoradiogram of rat fungiform papilla taste bud 200 hr after intra- 

 peritoneal injection of tritiated thymidine; x 1000. Notice labelled cells 

 within the taste bud. (From Beidler, 1961a.) 



What happens to the neural innervation of a single taste cell as it ages and 

 moves toward the center of the taste buds? This is not known. However, it 

 is very plausible that the nearest nerve fiber branches to innervate the newly 

 forming taste cell at the outer rim of the taste bud. The taste cell moves 

 toward the center of the taste bud at the slow rate of about 0.06///hr (lOA/ 

 min or 1.4/A/day). In this manner the taste fiber at the rim of the taste bud 

 would always innervate young taste cells in contrast to the fiber at the center 

 of the bud which would innervate the older cells. By this process the 

 specificity of single taste nerve fibers would be maintained even though 

 the individual receptor cells could continually age and change in their 

 response characteristics. 



CHARACTERISTICS OF TASTE CELL MEMBRANE 



Electron microscopy reveals that the cells within the taste bud are very 

 tightly packed so that there is little probability that taste stimuli applied to 



