Intrathecal injections

For intrathecal injections, hair was clipped from the back of each mouse at least 24 h before the experiment. All intrathecal injections were delivered in a total volume of 10 μL using a 30-gauge needle attached to a luer-tip 25 μL Hamilton syringe. The needle was inserted into the tissue at a 45° angle and through the fifth intervertebral space (L5 – L6). Solution was injected at a rate of 1 μL/s. The needle was held in position for 10 s and removed slowly to avoid any outflow of the solution. Only mice that exhibited a reflexive flick of the tail following puncture of the dura were included in our behavioral analysis. These procedures were performed in awake mice.