Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 57 2 2019 03 12 110 115 EN Alireza Mazarei a Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. b Department of Pharmacology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mojtaba Nasimi a Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. b Department of Pharmacology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Nastaran Rahimi a Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. b Department of Pharmacology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Mehdi Sanatkar Department of Anesthesiology and Critical Care, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Sina Tofigh a Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. b Department of Pharmacology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Amirhossein Orandi Department of Anesthesiology, School of Medicine, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran, Iran. Ahmad Dehpour Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran. AND Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. 2018 03 03 2018 12 15 Post anesthesia shivering which happens in some patients during recovery time after general anesthesia is followed by central hypothermia and peripheral vasoconstriction. In this study, the effect of opioidergic/nitrergic systems were determined on post anesthesia shivering in rat. Animals were cooled gently on a cold surface with indirect contact with a mixture of ice and water. Animals were treated with saline; methadone (a full opioid agonist, 10 mg/kg); naltrexone (an opioid receptor antagonist, 10 mg/kg); L-NAME (a nonselective nitric oxide synthase (NOS) inhibitor, 10 mg/kg). The core body temperature and the frequency of basal state- and post anesthetic-shivering were recorded using a stainless steel rectal probe (MLT-1403, AD Instruments®) and electromyography (EMG) electrodes connected to Animal Bio Amp (FE136, AD Instruments®) signal conditioner, respectively. Methadone administration reduced the frequency of shivering after anesthesia, while injection of naltrexone and L-NAME increased post anesthetic shivering compared to vehicle group. Co-administration of L-NAME and methadone showed a significant decrease the frequency of post anesthetic shivering. Furthermore, the temperature of shivering onset was reduced following methadone administration, which was blocked by injection of both naltrexone and/or L-NAME. To conclude, the findings of this study revealed the protective impact of methadone on post anesthesia shivering-induced with hypothermia dominated to nitrergic pathway effects in rat. https://acta.tums.ac.ir/index.php/acta/article/view/7086 https://acta.tums.ac.ir/index.php/acta/article/download/7086/5219