The sensation of taste is generated in taste buds, which then send the information through the gustatory nerves to the brain. The neurotransmitter between the taste buds and the nerve had been thought to be serotonin, but mice genetically manipulated to lack functional serotonin receptors sense taste stimuli normally. Finger et al. have investigated another candidate neurotransmitter that functions at these synapses, adenosine triphosphate (ATP). Mice lacking the two ionotropic receptors for ATP (P2X2 and P2X3) did not show responses to taste stimuli in the gustatory nerves. In addition, these mice could not detect most tastes in behavioral tests in which they had to show preference for one substance over another. These results, considered with the release of ATP from taste buds when they are stimulated, show that ATP is indeed the neurotransmitter at these synapses.
T. E. Finger, V. Danilova, J. Barrows, D. L. Bartel, A. J. Vigers, L. Stone, G. Hellekant, S. C. Kinnamon, ATP signaling is crucial for communication from taste buds to gustatory nerves. Science 310, 1495-1499 (2005). [Abstract] [Full Text]