Taste Reception.
Lindemann, Bernd.
Fachrichtung Physiologie, Universitat des Saarlandes, Homburs/Saar,
Germany.
APStracts 2:0012P, 1996.
ABSTRACT
Recent research on cellular mechanisms of peripheral taste has defined
transduction pathways involving membrane receptors, G proteins, second
messengers, and ion channels. Receptors for organic tastants received much
attention, because they provide the specificity of a response. Their future
cloning will constitute a major advance. Taste transduction typically utilizes
two or more pathways in parallel. For instance, sweet-sensitive taste cells of
the rat respond to sucrose with activation of adenylyl cyclase, followed by
adenosine 3[prime],5[prime]-cyclic monophosphate (cAMP)-dependent membrane
events and Ca[sup]2+[r] uptake. The same cells respond differently to some
artificial sweeteners, i.e., with activation of phospholipase C (PLC) followed
by inositol 1,4,5-trisphosphate (IP[inf]3[r])-dependent Ca[sup]2+[r] release
from intracellular stores. Some bitter tastants block K[sup]+[r] channels or
initiate the cascade receptor G[inf]i[r] protein, PLC, IP[inf]3[r], and
Ca[sup]2+[r] release or the cascade receptor à-gustducin, phosphodiesterase
(PDE), cAMP decrease, and opening of cAMP-blocked channels. Membrane-permeant
bitter tastants may elicit a cellular response by interacting with G protein,
PLC, or PDE of the above cascades. Salt taste is initiated by current flowing
into the taste cell through cation channels located in the apical membrane,
even though basolateral channels may also contribute (following salt diffusion
through paracellular pathways). In rodents, the Na[sup]+[r]-specific component
of salt taste is typically mediated by apical amiloride-sensitive Na[sup]+[r]
channels, but less specific and not amiloride-sensitive taste components exist
in addition. Sour taste may in part be mediated by amiloride-sensitive
Na[sup]+[r] channels conducting protons, but other mechanisms certainly
contribute. Thus the transduction of taste cells generally comprises parallel
pathways. Furthermore, the transduction pathways vary with the location of
taste buds on the tongue and, of course, across species of animals. To
identify these pathways and to understand how they are controlled and why they
evolved to this complexity are the major goals of the present research.
APS Manuscript Number P-6.
Article publication pending July 1996, Physiological Reviews.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96