Modulation of Neuropathic Pain by Galanin and Neuropeptide Y at the Level of the Medulla in Rats

This study was conducted to examine the role of galanin and neuropeptide Y (NPY) in the modulation of neuropathic pain at the level of the medulla. Under pentobarbital anesthesia, Sprague-Dawley rats were subjected to neuropathic surgery. Intracisternal injections of galanin and NPY were performed 2 weeks after nerve injury and mechanical allodynia was monitored. In an electrophysiological experiment, rats were reanesthetized with urethane and the responses of gracile nucleus neurons to mechanical stimulation were observed. Galanin and NPY were applied microiontophoretically. Intracisternally administered NPY reduced neuropathic pain behaviors in a dose-dependent manner. High doses of galanin inhibited neuropathic pain behaviors. Iontophoretically ejected galanin and NPY inhibited responses of gracile nucleus neurons to mechanical stimulation. These results suggest that galanin and NPY play a role in modulating neuropathic pain in the gracile nucleus of the medulla.