BDNF-TrkB Signaling Engages a Src Family Kinase-Pannexin 1 Pathway During the Onset of Sustained Mechanical Hyperalgesia.

Brain-derived neurotrophic factor (BDNF) is a key mediator of central sensitization and chronic pain through activation of TrkB receptors. Although the Pannexin 1 (Panx1) channel has been implicated in chronic pain, its involvement in BDNF-TrkB signaling remains unclear. Here, we investigated the functional relationship between TrkB activation and Panx1 using a BDNF-induced pain model in rats. Animals received a single intrathecal administration of BDNF, and mechanical nociception was assessed using the Randall-Selitto test. Behavioral analyses were combined with pharmacological interventions, Western blotting, confocal microscopy, YOPRO-1 uptake assays, and ATP quantification in spinal cord tissue. Intrathecal BDNF induced a robust mechanical hyperalgesia that persisted for up to 10 days. Blockade of Panx1 with 10Panx significantly attenuated BDNF-induced hyperalgesia. BDNF increased Src416 phosphorylation, Panx1 phosphorylation, and YOPRO-1 uptake in dorsal horn neurons, indicating enhanced channel activation. These effects were prevented by the TrkB antagonist ANA12, demonstrating that Panx1 acts downstream of BDNF-TrkB signaling. Inhibition of Src-family kinases with PP2 reduced both hyperalgesia and Panx1 activation, supporting a TrkB-Src-Panx1 signaling cascade. Furthermore, BDNF enhanced ATP release from spinal cord slices, an effect abolished by ANA12, PP2, and 10Panx. Together, these findings identify Panx1 as a downstream effector engaged by BDNF-TrkB signaling during the onset of mechanical hyperalgesia. While persistent TrkB activation appears to be required for the prolonged nociceptive state, the Src family kinase-Panx1 pathway contributes primarily to the early phase of BDNF-induced sensitization.