The brainstem pre-Bötzinger complex (preBötC) generates inspiratory breathing rhythms, but which neurons comprise its rhythmogenic core? Dbx1-derived neurons may play the preeminent role in rhythm generation, an idea well founded at perinatal stages of development but incompletely evaluated in adulthood. We expressed archaerhodopsin or channelrhodopsin in Dbx1 preBötC neurons in intact adult mice to interrogate their function. Prolonged photoinhibition slowed down or stopped breathing, whereas prolonged photostimulation sped up breathing. Brief inspiratory-phase photoinhibition evoked the next breath earlier than expected, whereas brief expiratory-phase photoinhibition delayed the subsequent breath. Conversely, brief inspiratory-phase photostimulation increased inspiratory duration and delayed the subsequent breath, whereas brief expiratory-phase photostimulation evoked the next breath earlier than expected. Because they govern the frequency and precise timing of breaths in awake adult mice with sensorimotor feedback intact, Dbx1 preBötC neurons constitute an essential core component of the inspiratory oscillator, knowledge directly relevant to human health and physiology.

Significance Statement Breathing behavior depends on rhythmic movements. The underlying neural rhythm for inspiration may originate due to brainstem interneurons defined genetically by expression of the embryonic transcription factor Dbx1. Dbx1-derived neurons comprise the core oscillator microcircuit in perinatal mice, but they serve other functions too, and their inspiratory rhythmogenic role has not been conclusively tested in adults. Optogenetic photostimulation and photoinhibition of Dbx1-derived brainstem neurons in intact adult mice modulated breathing, either speeding it up, slowing it down to the point of apnea (no breathing), or perturbing its phase, which are functions consistent with the rhythm generator. These results establish the cellular point of origin for breathing rhythm, a key physiologic brain function in humans and all mammals.

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