The correlation between pain-related behaviour and spinal microgliosis in four distinct models of peripheral neuropathy.
Blackbeard J., Wallace VCJ., O'Dea KP., Hasnie F., Segerdahl A., Pheby T., Field MJ., Takata M., Rice ASC.
BACKGROUND: Peripheral nerve injury is associated with a spinal microglial response that has been correlated with the development of behaviours reflective of neuropathic pain. METHODS: To examine whether this phenomenon is generalizable to neuropathic pain of non-traumatic aetiology, this study investigated the association between spinal microgliosis and behavioural measures of neuropathic hypersensitivity and pain-related anxiety behaviour in four distinct rat models of peripheral neuropathic pain. These were traumatic neuropathy [L5 spinal nerve transection (SNT)], HIV-related neuropathies (either treatment with the antiretroviral drug Zalcitabine (ddC) or combination of perineural exposure to the HIV-gp120 protein and ddC treatment) and varicella zoster virus (VZV) infection. RESULTS AND CONCLUSION: Persistent mechanical hypersensitivity developed in all 'neuropathic' rats. However, spinal microgliosis, as measured by increased CD11b/c immunohistochemical staining and increased numbers of cells expressing CD11b measured by flow cytometry, was evident in the SNT and to a lesser extent in the HIV neuropathy models but not the VZV model. These results suggest that behavioural hypersensitivity and thigmotaxis can only be linked to a microglial response in certain models of neuropathy.