Sex differences in the development of localized and spread mechanical hypersensitivity in rats after injury to the infraorbital or sciatic nerves to create a model for neuropathic pain

• Published in: Gender medicine 2009, Vol.6, p.225-234
• Main Authors: Dominguez, Cecilia A., PhD, Kouya, Poli Francois, PhD, Wu, Wei-Ping, MD, PhD, Hao, Jing-Xia, PhD, Xu, Xiao-Jun, PhD, Wiesenfeld-Hallin, Zsuzsanna, PhD
• Format: Article
• Language: English
• Subjects: Analysis of Variance; Animals; Cranial Nerve Injuries - etiology; Facial Pain - physiopathology; Female; Hypersensitivity - etiology; infraorbital nerve; Internal Medicine; Male; Medicin och hälsovetenskap; Models, Theoretical; neuropathic pain; rat; Rats; sciatic nerve; Sciatic Nerve - injuries; Sciatic Neuropathy - etiology; sex differences; Sex Differentiation; Sex Factors; trigeminal neuralgia; Trigeminal Neuralgia - physiopathology
• ISSN: 1550-8579; 1878-7398; 1878-7398
• DOI: 10.1016/j.genm.2009.01.003

Abstract Background: Neuropathic pain after injury to the nervous system is a difficult clinical problem. Sex differences in the development of neuropathic pain have not been well established experimentally or clinically. Objective: Rats were used to examine sex differences in localized and spread mechanical hypersensitivity after partial injury to their infraorbital or sciatic nerves in a model of neuropathic pain. Methods: In adult female and male rats, partial nerve injury to the infraorbital and sciatic nerves was produced using a photochemical method. Mechanical hypersensitivity (allodynia) was examined and compared in the innervation territories of the nerves on the face or hind paw. The spread of hypersensitivity beyond the innervation territories of the injured nerves was also studied. The female and male rats were randomized to active and sham groups. The rats in the sham group had their sciatic or infraorbital nerve exposed, but not injured. Results: A total of 67 rats (36 females, 31 males) were used. There was a marked sex difference in the response to infraorbital nerve injury: female rats developed more profound and long-lasting facial hypersensitivity than did male rats ( P male, P < 0.001). Sham-group rats did not exhibit localized or spread mechanical hypersensitivity. Conclusion: Sex differences in the development of neuropathic painlike behaviors in rats were dependent on site of injury and site of testing, with female rats being more susceptible to the development of spread mechanical hypersensitivity, particularly after facial nerve injury, compared with male rats.