Behavioural and microglial effect of cannabinoids in neuropathic pain
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AbstractChronic pain is a disease affecting 1 in 5 Canadians and the leading cause of disability worldwide. Among the most debilitating forms of chronic pain is neuropathic pain, which is caused by injury or disease of the nervous system. Neuropathic pain is difficult to manage clinically because it is often resistant to strong analgesics including opioids. Since therapeutic options are limited, some patients resort to medical cannabis to alleviate pain symptoms. Pain is the most common medical reason to use cannabis and cannabinoids. However, the efficacy of cannabis for pain, as well as its potential health impacts, are not well defined. My project addresses this knowledge gap by characterizing the behavioural and cellular effects of cannabis in the rat spared nerve injury (SNI) model. This neuropathic pain model replicates the mechanical pain sensitivity reported in neuropathic pain patients, including mechanical allodynia, which is an abnormal sensitivity to tactile stimuli in which even light touch can elicit pain. Prior research shows that microglia, the resident immune cells of the central nervous system, play a central role in the development of chronic neuropathic pain after peripheral nerve injury in males. In this study, we assessed the effects of vaporized whole cannabis extract and a combination of THC and CBD on mechanical hypersensitivity in spared nerve injury (SNI) male and female Sprague-Dawley rats. I also investigated the effect of cannabinoid exposure on spinal microglia. I find that cannabis and cannabinoid extracts transiently reversed mechanical allodynia in the spared nerve injury model of neuropathic pain in a sex- and compound-dependent manner. Additionally, I demonstrate a compound-dependent effect of cannabinoids on microglial reactivity.
CitationDavidson, C. E. D. (2022). Behavioural and microglial effect of cannabinoids in neuropathic pain (Unpublished master's thesis). University of Calgary, Calgary, AB.
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