Mouse Taste Cells Discriminate Sweet and Sour Tastes by Releasing Neurotransmitters

Researchers now report that taste buds stimulated with a sour taste elicit robust responses in closely placed GABA biosensors indicating  the presence of  inhibitory neurotransmitters in mouse taste buds and that these neurotransmitters play an important role in modulating taste responses.

The gustatory system detects sweet, sour, bitter, salty, umami, and possibly fatty tastes. The sense of taste plays an important role for accepting or rejecting food and serves to protect us from ingesting harmful substances, but also causes the behavioral preferences to some types of foods. Taste begins with the stimulation of gustatory receptor cells located in taste buds on the tongue and in the oral cavity.

Taste cells release transmitters to stimulate primary afferent sensory fibers and transmit gustatory information to the brain. In addition, taste transmitters also regulate the function of the adjacent taste cells. It is now being recognized there is a significant degree of information processing in the taste buds during gustatory stimulation. This information processing involves cell-to-cell communication within the taste bud using neurotransmitters such as ATP, norepinephrine (NE), serotonin (5-HT), and γ-aminobutyric acid (GABA).

Over the past several years, Drs Yijen Anthony Huang, Elizabeth Pereira and Stephen  Roper at the Miller School of Medicine, University of Miami, Miami, FL, have innovated a powerful technique using genetically-engineered biosensors, to study whether and how taste bud cells release transmitters by real-time Ca2+ imaging.

Their new research finding using this technique was published this month in the open access journal PLoS ONE.

In the present article by using GABA biosensors, they reported that sour (acid) but not sweet and bitter tastes elicits GABA release from the specific type, Type III (Presynaptic), cells. Next, by using ATP biosensors they showed that GABA reduces taste-evoked ATP secretion from Type II (Receptor) cells. GABA is considered to be an inhibitory transmitter in taste buds. Interestingly, their findings showed that taste bud cells are able to release different taste transmitters elicited by different taste modalities. These data suggest that transmitters modulate the activity of taste cells before the final output has been sent to afferent fibers.

“The importance of knowing the transmitters involved in taste reception cannot be underestimated,” said Huang, Research Assistant Professor of Physiology & Biophysics. “Taste modification by manipulating neurotransmission within the taste bud will be potentially considered once we know more about taste transmitters and their receptors.” This is one important rationale for studying taste bud neurotransmitters because taste modification has implications for diet selection (such as obesity), compliance in taking medications (namely, by suppressing drug bitterness), and enhancing the quality of life.

Science news reference: Huang YA, Pereira E, Roper SD. Acid Stimulation (Sour Taste) Elicits GABA and Serotonin Release from Mouse Taste Cells. 2011.  PLoS ONE 6(10): e25471. doi:10.1371/journal.pone.0025471