In fruit flies, neurons choreograph feeding in milliseconds

A fruit fly’s sip lasts only a moment, but inside its throat the action unfolds as a tightly staged relay. Researchers filmed awake flies drinking a dyed sugary solution at 120 frames per second, while microscopic electrodes recorded the electrical activity of feeding motor neurons. The new study, published in Nature Neuroscience, identified the sequence that drives the pump.

The order ran from front to back: MN12V, MN12D, MN11V, MN11D and MN10. First the food cavity opened, then its front and back sections expanded in turn; finally, the opening closed and pushed liquid into the esophagus. The same firing pattern held across different feeding speeds, suggesting that the circuit preserves its order while changing the pace of the behavior.

The neurons were not merely carrying instructions to muscles. The first active neuron released glutamate, a chemical signal that did two jobs at once: it contracted the muscle it controlled and silenced a nearby inhibitory neuron. With that brake removed, the next motor neuron fired. The chain reaction created a wave of contractions timed in milliseconds.

The researchers tested that explanation by using CRISPR gene editing to remove glutamate-gated chloride receptors, the molecular receivers that let the inhibitory cells be switched off. The flies’ feeding pumps then became slower and uncoordinated. Separate experiments in genetically modified flies showed that all five pumping motor neurons were physically connected through electrical pathways.

And what does that change in concrete terms? It gives researchers a clearer circuit-level explanation for how a simple intention becomes a rapid, multi-muscle action. Feeding, swallowing and breathing all depend on coordinated sequences, but this result is limited to a fruit-fly laboratory model: it does not yet show that the same wiring or mechanism operates in people.