Arachidonoyl‐2‐chloroethylamide alleviates inflammatory pain in a sex‐dependent manner using the formalin test

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Previous studies have shown that certain cannabinoids have analgesic effects. Specifically, activation of cannabinoid receptor (CB) 1 has been demonstrated to produce analgesia in multiple animal models. Arachidonyl‐2‐chloroethylamide (ACEA) is a synthetic agonist for CB1 receptors. The activation of CB1 with ACEA could enable chronic inflammatory pain patients to manage this discomfort. ACEA has not been extensively studied in animal models; therefore, not much is known about the dose effectiveness, development of tolerance, or sex‐specific effects.To study the analgesic effects of ACEA, we treated male and female C57BL6J mice prior to the formalin pain test. Administration of formalin (2.5% intraplantar) produces a biphasic pain response, modeling both acute and inflammatory pain. We believe that administration of ACEA at a dose of 0.5 mg per kg intraperitoneal will reduce inflammatory pain in this model. Also, we suggest that daily pretreatment with ACEA prior to the formalin test will cause desensitization to this compound; therefore, the initial analgesic effect will not be seen. To examine sex‐specific effects, we also tested and compared male and female mice. Moreover, vaginal lavage was performed daily on female mice to track the estrous cycle.Preliminary data suggests that females experience higher pain sensitivity compared with males when ACEA 0.5 mg per kg was used. Furthermore, our preliminary data shows that chronic administration in females results in estrous cycle changes. We concluded that there is a sex‐dependent difference in analgesic response to ACEA, and that it may be hormonally‐mediated.Support or Funding InformationFunded by NIDA DA044999‐01A1 (JG) and Texas Tech University Health Sciences Center School of Medicine #121035 (JG).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.