Background: Patients with neuropathic pain frequently express osteoporosis. We have reported that an animal model of neuropathic pain induced by partial sciatic nerve ligation (PSNL mice) exhibits osteoporosis. In this study, we investigated the effects of amitriptyline, a potent analgesic drug for neuropathic pain, on bone loss in PSNL mice.
Methods: Osmotic pumps were used for chronic treatment with amitriptyline. We implanted an osmotic pump to PSNL mice subcutaneously at 7 days after nerve ligation. Then, bone tissues were harvested after 3 weeks, and their structure were assessed by micro computed tomography.
Results: As previously reported, mechanical hypersensitivity was developed in the ipsilateral paw after 7 days of partial nerve ligation, and it sustained more than 4 weeks. Changes of trabecular bone parameters indicate that PSNL mice have osteoporosis in their legs. By chronic treatment with amitriptyline, mechanical hypersensitivity was continuously attenuated and bone loss was suppressed in PSNL mice.
Conclusion: Amitriptyline, a tricyclic antidepressant, may have a clinical benefit for the treatment of neuropathic pain accompanied with osteoporosis.

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