Temporal single-cell profiling of the parabrachial <i>Calca</i> neurons reveals molecular dynamics driving nociplastic pain

<jats:p> Parabrachial <jats:italic>Calca</jats:italic> neurons are necessary for chronic pain and sufficient to drive nociplastic pain in mice, but how they sustain a pain state that outlasts its trigger is unknown. We performed temporal single-cell mRNA sequencing of the parabrachial nucleus (PBN) across the onset, chronic, and recovery phases of <jats:italic>Calca</jats:italic> neuron-driven tactile allodynia, using fixed-tissue profiling and reference-atlas registration to track molecularly defined populations over time. Activation broadly induced immediate-early genes, after which <jats:italic>Calca</jats:italic> neurons displayed changes in expression of genes that affect signaling and synaptic plasticity, with bidirectional changes that mirrored the onset and resolution of allodynia. The gene encoding brain-derived neurotrophic factor ( <jats:italic>Bdnf</jats:italic> ) remained persistently elevated in the chronic phase. BDNF infusion in the PBN prolonged allodynia, whereas blockade of its receptor (TrkB) attenuated it, and inactivating the <jats:italic>Bdnf</jats:italic> gene in <jats:italic>Calca</jats:italic> neurons abolished their hyperexcitability, attenuated allodynia, and relieved pain in a migraine model. These observations pinpoint BDNF as a driver of persistent nociplastic pain. </jats:p>