I am a
Home I AM A Search Login

Papers of the Week

Papers: 16 May 2020 - 22 May 2020

Animal Studies, Pharmacology/Drug Development

2020 May 08


Daily intermittent fasting in mice enhances morphine-induced anti-nociception while mitigating reward, tolerance, and constipation.


The opioid epidemic has plagued the United States with high levels of abuse and poor quality of life for chronic pain patients requiring continuous use of opioids. New drug discovery efforts have been implemented to mitigate this epidemic, however, new medications are still limited by low efficacy and/or high side effect and abuse potential. Intermittent fasting (IF) has recently been shown to improve a variety of pathological states, including stroke and neuroinflammation. Numerous animal and human studies have shown the benefits of IF in these disease states, but not in pain and opioid treatment. We thus subjected male and female CD-1 mice to 18-hour fasting intervals followed by 6-hour feed periods with standard chow for 1 week. Mice which underwent this diet displayed an enhanced anti-nociceptive response to morphine both in efficacy and duration using thermal tail flick and post-operative paw incision pain models. While showing enhanced anti-nociception, IF mice also demonstrated no morphine reward and reduced tolerance and constipation. Seeking a mechanism for these improvements, we found that the mu opioid receptor (MOR) showed enhanced efficacy and reduced tolerance in the spinal cord and periaqueductal grey (PAG) respectively from IF mice using a S-GTPγS coupling assay. These improvements in receptor function were not due to changes in MOR protein expression. These data suggest that a daily IF diet may improve the therapeutic index of acute and chronic opioid therapies for pain patients in the clinic, providing a novel tool to improve patient therapy and reduce potential abuse.