Optogenetic stimulation attenuates central post-stroke pain via BDNF/TrkB signaling pathway modulation in the ascending pain modulation system.

To investigate the role of BDNF/TrkB signaling in Central Post-Stroke Pain (CPSP) and to investigate whether this signaling is related to the analgesic effect of optogenetics. This study was conducted in two parts. First, 40 rats were acquired and randomly divided into four groups: Sham, CPSP, CPSP + ANA-12 (inhibitor of the BDNF/TrkB signaling pathway), and CPSP + 1% DMSO. The Sham group received a saline injection into the Ventral Posterolateral Nucleus of the Thalamus (VPL), whereas the other three groups were injected with type IV collagenase. Additionally, the two groups of CPSP rats were separately injected with ANA-12 or 1% DMSO in the VPL. Second, 50 rats were acquired and randomly divided into five groups: Sham, CPSP, CPSP + NpHR, CPSP + NpHR + BDNF, and CPSP + NpHR + PBS. From day 3 after collagenase injection, rats in the three NpHR groups received yellow laser stimulation at a wavelength of 589 nm six times a day for 12 consecutive days. Subsequently, two groups of stimulated rats were separately injected with BDNF or PBS in the VPL. Optogenetic therapy effectiveness and potential mechanisms were evaluated using pain threshold tests and molecular biology, among other methods. According to the pain threshold test results, optogenetic therapy and ANA-12 injection reversed aberrant CPSP while downregulating BDNF and TrkB. Conversely, exogenous BDNF injection reversed the therapeutic effect of optogenetics on pain. The BDNF/TrkB signaling pathway in the ascending pain modulation system may crucially modulate CPSP in rats. Furthermore, optogenetic therapy could suppress BDNF/TrkB signaling in the ascending pain modulation system, potentially alleviating thalamic hemorrhage-induced Neuropathic Pain (NP).