2.6. Spinal nerve ligation model

Spinal nerve ligation (SNL) was performed as described previously (Jiang et al., 2016; Lu et al., 2014). After the experimental rats were anaesthetized using 3% pentobarbital sodium (50 mg·kg⁻¹), the L5–6 spinal nerves were ligated and cut, with the L4 spinal nerves left intact. On day 7 after SNL, the paw withdrawal threshold was determined using von Frey filaments. To assess its modulatory role in SNL rats, activin C was dissolved in 20 μl of PBS containing 0.2% BSA and then intrathecally injected in the experimental rats. The paw withdrawal threshold was measured at indicated time points.