Rôle of nerve and epithelium in the regulation of alkaline phosphatase activity in gustatory papillae

Abstract

The loss of alkaline phosphatase activity from the gustatory epithelium of the rat's vallate papilla after glossopharyngeal nerve transection indicates that the enzyme is neurally regulated. The absence of this enzyme from the gustatory epithelium of the fungiform papillae innervated by the chorda tympani nerve suggests that these two nerves may differ in their capacity to regulate this enzyme. Since alkaline phosphatase is present throughout all the folds of the foliate papilla and since this papilla is innervated by glossopharyngeal and chorda tympani nerves, selective nerve sections should answer the question as to whether the chorda tympani nerve is capable of maintaining alkaline phosphatase activity. Two weeks after chorda tympani nerve section alone, taste buds and alkaline phosphatase activity were absent from the anterior folds but present posteriorly, while after glossopharyngeal nerve section alone, buds and enzyme were absent in the posterior folds but present anteriorly. It was only after combined chorda tympani and glossopharyngeal nerve transection that all taste buds and alkaline phosphatase disappeared. The only additional change 20 weeks after the respective nerve sections was a greater epithelial atrophy of the denervated folds. The results indicate that the regulation of alkaline phosphatase is not gustatory-nerve specific, but is a property common to both chorda tympani and glossopharyngeal nerves. The relative independence of alkaline phosphatase of the type of gustatory innervation stresses the importance of continued studies of both nerves and epithelium in gustatory function.