Modulation of Invading and Resident Inflammatory Cell Activation as a Novel Way to Mitigate Spinal Cord Injury Associated Neuropathic Pain

Abstract : The aim of our research over the past two years was to investigate the therapeutic effect of the non-psychoactive cannabinoid cannabidiol (CBD) on spinal cord injury neuropathic pain (SCI-NP) and associated inflammation. Changes in thermal and mechanical hind-paw sensitivity were determined following moderate spinal cord contusion injury (level T9-1 O) in female C57BV5 mica treated with vehicle or CBD. Additional groups were run to assess the effect of SCI and CBD treatment on microglial activation and peripheral immune cell invasion In the spinal cord. CBD treated mice showed less neuropathic pain than vehicle-treated controls; however CBD treatment failed to improve locomotor and bladder function following SCI. CBD decreased cytokine and chemokine expression and T cell Invasion into the spinal cord following spinal cord injury. CBD did not decrease microglial activation or number. These results suggest that CBO's ability to attenuate recruitment of T cells into the damaged cord leads to a reduction In the development of neuropathic pain but not an improvement of motor or bladder function . More recent experiments have also shown that exposure to low dose chronic morphine exacerbates SCI neuropathic pain while exposure to higher dose chronic morphine attenuates SCI neuropathic pain. The role of T cell and microglial activation following these exposures is currently being evaluated.