Fungiform papillae

FIGURE 50-7 Rattongue, taste papillae and taste buds. (A) Surface of the rat tongue showing location of the taste papillae. (B) Cross-section of the three main types of taste papillae fungiform, foliate and vallate. (C) The taste bud contains 50-100 taste cells, including receptor cells and basal cells. 

Studies on human taste sensations confirm and extend our understanding of the types of chemical signals measured by these oral chemoreceptor systems. There are, for instance, several distinct sensations elicited by chemical stimulation of fungiform papillae innervated by the geniculate ganglion, indicating that a neural functional complexity similar to that described above for... 

PROP status. Individuals classified as tasters of the bitter compound propylthiouracil (PROP) (not found in wine) have been reported to perceive bitterness more intensely and have a higher number of taste pores per taste bud and higher density of fungiform taste papillae on the tongue than non-tasters of PROP (32- 36). Despite this, PROP status has not been demonstrated to affect perception of bitterness or astringency of phenolic compounds in wine (73, 29) or water (75, 77, 79, 30). 

Sour taste detects acids, i.e., protons. Several different sour taste receptor candidates such as acid-sensing ion channels (ASICs) (57), hyperpolarization-activated cyclic nucleotide-gated channels (HCNs) (58), and two pore domain potassium channels (K2PS) (59, 60) have been described in the past. In addition, recent research identified two members of the polycystic kidney disease (PKD) family of the transient receptor potential superfamily (TRP) as strong sour taste receptor candidates or as part thereof. Immunohistochemistry and in situ hybridization revealed the presence of the polycystic-kidney-disease-like ion channel PKD2L1 in subsets of taste receptor cells of mouse fungiform, vallate, and foliate papillae. These cells differ from... 

TRC from fungiform papillae and some of the anterior foliate papillae establish synaptic contacts with the chorda tympani (CT) nerve, whereas the posterior parts of the foliate and circumvallate papillae are innervated by the glossopharyngeal (GL) nerve. The possible involvement of gustatory nerves in the LCFA-mediated fat preference has recently been explored in rodents, by studying the impact of bilateral transection of the CT nerve (CTX) and/or bilateral transection of the GL nerve (GLX). 

Cottier-Fox M, Arvidson K, Hammarlune E, Friberg U. 1987. Fixation and occurrence of dark and light cells in taste buds of fungiform papillae. Scand J Dental Res 95 417-427. 

On the tongue, the chemesthetic neurons are located in the papillae and are wrapped around the taste buds. The fungiform papillae, though lacking taste cells, possess chemesthetic neurons. These neurons make use of the structure of the taste bud to form a channel to the tongue surface. It has been reported that these neurons outnumber taste receptors nerves three to one [32]. The chemesthetic neurons are similar to taste receptors in that they have chemical specific receptors sites, however, they differ in that the neurons possess a set of other unique receptors. These receptors include mechanoreceptors for tactile response, thermoreceptors that detect temperature change, proprioceptors that detect motion, and nociceptors that mediate pain (comprise the somatosenses as a whole) [33]. 

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