A TAS1R receptor-based explanation of sweet 'water-taste'.
'Water-tastes' are gustatory after-impressions elicited by water following the removal of a chemical solution from the mouth, akin to colour after-images appearing on 'white' paper after fixation on coloured images. Unlike colour after-images, gustatory after-effects are poorly understood. One theory posits that 'water-tastes' are adaptation phenomena, in which adaptation to one taste solution causes the water presented subsequently to act as a taste stimulus. An alternative hypothesis is that removal of the stimulus upon rinsing generates a receptor-based, positive, off-response in taste-receptor cells, ultimately inducing a gustatory perception. Here we show that a sweet 'water-taste' is elicited when sweet-taste inhibitors are rinsed away. Responses of cultured cells expressing the human sweetener receptor directly parallel the psychophysical responses-water rinses remove the inhibitor from the heteromeric sweetener receptor TAS1R2-TAS1R3, which activates cells and results in the perception of strong sweetness from pure water. This 'rebound' activity occurs when equilibrium forces on the two-state allosteric sweet receptors result in their coordinated shift to the activated state upon being released from inhibition by rinsing.
Galindo-Cuspinera
Veronica
V
Monell Chemical Senses Center, 3500 Market Street, Philadelphia, Pennsylvania 19104, USA.
Winnig
Marcel
M
Bufe
Bernd
B
Meyerhof
Wolfgang
W
Breslin
Paul A S
PA
D000222:Adaptation, Physiological / Q000187:drug effects / Q000502:physiology; D000494:Allosteric Regulation / Q000187:drug effects; D006801:Humans; D008954:Models, Biological; D018094:Receptors, Metabotropic Glutamate / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012439:Saccharin / Q000494:pharmacology; D013649:Taste / Q000187:drug effects* / Q000502:physiology*; D014867:Water / Q000378:metabolism / Q000494:pharmacology*
D018094:Receptors, Metabotropic Glutamate; D014867:Water; D012439:Saccharin