When organisms consume foods or drinks with a mixture of tastes, like sweet and sour, how do their taste buds communicate this taste information to the brain? New in JNeurosci, Stephen Roper and colleagues, at the University of Miami Miller School of Medicine, advanced understanding by measuring how signals pass from the tongue to the brain in mice during exposure to mixed tastes.
By comparing neural responses under different taste conditions, the researchers found that sourness triggered neural activity that dampened responses to sweetness, bitterness, and saltiness. The research team further discovered that sourness suppression of neural responses to other tastes was not limited to a subset of neurons in the pathway from the tongue to the brain and that these neurons essentially categorized tastes into two bins: pleasant or unpleasant.
Probing the mechanism for sourness suppression of other tastes, the researchers manipulated levels of a neurotransmitter that sour-responsive cells release within each taste bud called serotonin. Increasing serotonin in taste buds strengthened sourness suppression of other tastes, while, in contrast, depleting serotonin weakened the effect. These findings suggest that sweetness, bitterness, and saltiness may be dampened by sourness before taste information reaches neurons.
Says Roper, "Taste buds not only respond to and transduce taste compounds, they also integrate and manipulate gustatory signals before transmitting them to the brain. The neurons that collect signals produced in taste buds are themselves organized into two large groups or clusters—neurons that convey gustatory signals associated with pleasure and neurons that convey unpleasant taste signals." According to the researchers, these data may inform future studies probing the "genetic signatures" of these neurons and whether altering these genes can manipulate taste.
