A neural basis for tonic suppression of sodium appetite

Sodium appetite is a powerful form of motivation that can drive ingestion of high, yet aversive concentrations of sodium in animals that are depleted of sodium. However, in normal conditions, sodium appetite is suppressed to prevent homeostatic deviations. Although molecular and neural mechanisms underlying the stimulation of sodium appetite have received much attention recently, mechanisms that inhibit sodium appetite remain largely obscure. Here we report that serotonin 2c receptor (Htr2c)-expressing neurons in the lateral parabrachial nucleus (LPBNHtr2c neurons) inhibit sodium appetite. Activity of these neurons is regulated by bodily sodium content, and their activation can rapidly suppress sodium intake. Conversely, inhibition of these neurons specifically drives sodium appetite, even during euvolemic conditions. Notably, the physiological role of Htr2c expressed by LPBN neurons is to disinhibit sodium appetite. Our results suggest that LPBNHtr2c neurons act as a brake against sodium appetite and that their alleviation is required for the full manifestation of sodium appetite. High concentrations of sodium are normally unpalatable. This study shows a neural population in the brainstem that suppresses appetite for sodium. Reducing the activity of these neurons can drive ingestion of high concentrations of sodium.