Motor neurons controlling fluid ingestion in Drosophila.

Rhythmic motor behaviors such as feeding are driven by neural networks that can be modulated by external stimuli and internal states. In Drosophila, ingestion is accomplished by a pump that draws fluid into the esophagus. Here we examine how pumping is regulated and characterize motor neurons innervating the pump. Frequency of pumping is not affected by sucrose concentration or hunger but is altered by fluid viscosity. Inactivating motor neurons disrupts pumping and ingestion, whereas activating them elicits arrhythmic pumping. These motor neurons respond to taste stimuli and show prolonged activity to palatable substances. This work describes an important component of the neural circuit for feeding in Drosophila and is a step toward understanding the rhythmic activity producing ingestion.