Ionotropic Receptor 76b Is Required for Gustatory Aversion to Excessive Na+ in Drosophila

Avoiding ingestion of excessively salty food is essential for cation homeostasis that underlies various physiological processes in organisms. The molecular and cellular basis of the aversive salt taste, however, remains elusive. Through a behavioral reverse genetic screening, we discover that feeding suppression by Na -rich food requires ( ) in labellar gustatory receptor neurons (GRNs). Concentrated sodium solutions with various anions caused feeding suppression dependent on . Feeding aversion to caffeine and high concentrations of divalent cations and sorbitol was unimpaired in -deficient animals, indicating sensory specificity of dependent Na detection and the irrelevance of hyperosmolarity-driven mechanosensation to -mediated feeding aversion. -dependent Na -sensing GRNs in both L- and s-bristles are required for repulsion as opposed to the previous report where the L-bristle GRNs direct only low-Na attraction. Our work extends the physiological implications of from low-Na attraction to high-Na aversion, prompting further investigation of the physiological mechanisms that modulate two competing components of Na -evoked gustation coded in heterogeneous -positive GRNs.