Introduction
Drug addiction is a chronic and recurrent brain disease, which is characterized by compulsive seeking drug and intense drug craving (Shippenberg et al., 2007a; Zhu et al., 2015; Wu et al., 2016). Opioid addiction is the accumulated results of tolerance and dependence, mainly including physical dependence and psychological dependence. Physical dependence seeks drug repeatedly and increases gradually the dose of the drug to avoid withdrawal symptoms (Nestler et al., 1993). Psychological dependence refers to the craving for seeking drug and euphoria achieved by repeated medication, which is not easy to eliminate, prompting to relapse. Drug relapse can persist a long time after the cessation of drug use in the human (Robbins et al., 2008) and the high rate of relapse after detoxification is a major clinical problem and becomes severe challenge to treat drug abuse (Aguilar et al., 2009). Morphine and related opioids are the most potent and widely used analgesics for treating moderate to severe pain. However, the development of physical and psychological dependence is an important limitation to use opioid drugs in the treatment of chronic pain, leading to misappropriate use and abuse liability (Ruzza et al., 2019). Drug addiction in western countries particularly in the USA has become a health and social problem in recent years that needs to be urgently addressed and is a unmet medical need (Wingo et al., 2016; Ezard et al., 2018).