Taste and behavior are hardwired into the brain
1/20/2006 - Different tastes are associated with different behavior, and it is all controlled by specific cells in the brain, says new research from UC Berkeley, findings that could have implications for the food industry.
In a study involving the humble fruit fly, Drosophila, the researchers were able to monitor behavioral effects of activating fly taste neurons.
"Although the decision to eat or not is critical for an animal's survival, little is known about the neural processing underlying taste acceptance or avoidance in any organism," wrote lead-author Sunanda Marella, in the journal Neuron (Vol. 49, Issue 2).
Drosophila were chosen due to the simplicity of the organism. In earlier studies the same team, led by Professor Kristin Scott, showed that specific neurons responded to sugar (Gr5a), while another neuron (Gr66a) responded to bitter tastes. In this new study, the researchers used fluorescent labels to signal activation in Gr5a and Gr66a.
In one experiment, flies were starved overnight and given a choice of a neutral substance or a substance plus taste (either sweet or bitter). The researchers found that the flies were attracted to substances that activated the Gr5a neuron, but avoided the substances that activated the Gr66a neuron.
"Artificial activation of Gr5a cells should be sufficient to generate acceptance behavior, whereas activation of Gr66a would elicit avoidance," the researchers predicted.
To test this hypothesis, special flies were engineered so that the hot pepper compound capsaicin would activate either Gr5a or Gr66a. Normal flies do not respond to the hot pepper taste.
The researchers found that the Gr5a activated flies were attracted to the pepper, while those with activated Gr66a avoided the pepper.
"Taste behaviors are hardwired to selective cell activation on the tongue of mammals and the proboscis in flies," concluded Marella.
The results may have implications for the food industry, said Scott, who told FoodNavigator-USA.com: "The principle is exactly the same in humans, in terms of how we detect sweet or bitter tastes."
"This would allow you to design molecules to activate specific cells to give you a targeted approach," said Scott.
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