Intrathecal Capsaicin and Capsazepine in Mice

The drug was administered intrathecally to mice by direct lumbar puncture as described previously (Pan et al., 2018 (link)). Control group received topical applications of PBS. For mice in capsaicin group, lumbar puncture was performed using a 5-μL Hamilton microsyringe (Hamilton, United States) fitted with a 30-G needle to deliver 2 μL capsaicin (2 mg/mL, Abmole, United States) into the subdural space of the spinal L4–L6 levels in non-anaesthetized mice before surgery (Jiang et al., 2023 (link)). For mice in capsazepine group, 0.5 μL capsazepine (2 mg/mL, Abmole, United States) was injected by lumbar puncture per day. Successful puncture was indicated by a reflexive lateral flick of the tail. For mice in capsazepine + CGRP group, CGRP overexpression lentivirus 10 μL (2.88 × 10⁸ TU/mL, GeneCopoeia Co., China) was injected around the femoral bone defect locally.