Hindbrain neurons that underlie water discrimination and consumption

Drinking water is essential for maintaining body fluid homeostasis. Animals can identify aqueous liquids from available options through ingestion and selectively consume them, indicating sensory abilities to detect ingested water. However, the underlying neural mechanisms remain unknown. Here, in mice, whole-brain neuronal activity mapping and Ca²⁺ imaging identified the waist area of the parabrachial nucleus (wPBN) as both responsive to and necessary for water drinking. Within this region, a neuronal population expressing the oxytocin receptor was enriched for neurons selectively responsive to ingested water. Closed-loop optogenetic inhibition of these neurons at the onset of drinking led to immediate cessation of water intake. Moreover, silencing this population impaired the ability to discriminate water from non-aqueous liquids but not water-seeking behavior. This study provides evidence for a neuronal population that encodes sensory information for the perception of water and its consumption, advancing our understanding of the neural basis of hydration.