Effects of Dextromethorphan on Nicotine-Induced Reward, Behavioral Sensitization, Withdrawal Signs, and Drug Seeking-Related Behavior in Rats

Introduction Tobacco products are addictive, with nicotine serving as the major addictive ingredient. Chronic tobacco use or chronic administration of nicotine alone results in both physiological and psychological dependence. Our previous studies indicated that dextromethorphan (DM) could effectively attenuate the dependence of morphine and methamphetamine. Thus, we further investigated the possible effects of DM on nicotine dependence. Aims and Methods Conditioned place preference (CPP) test was used to examine nicotine-induced rewarding effects as well as the drug-seeking-related behavior in rats. Nicotine dependence was induced by continuous subcutaneous infusion of nicotine via an osmotic minipump for 7 days and abstinence was initiated by removal of the pump. Withdrawal signs were observed and quantified. Locomotor activity was measured to determine the behavioral sensitization induced by nicotine. To investigate the activity of mesolimbic dopaminergic neuronal activity in correlation with the effects of nicotine, the animals were sacrificed and the nucleus accumbens (NAc), dorsal striatum (DS), and medial prefrontal cortex (mPFC) were dissected and used to determine the contents of dopamine (DA) and its metabolites using high-performance liquid chromatography (HPLC). Results Our results showed that DM could suppress nicotine-induced rewarding effect and drug-seeking-related behavior. In addition, co-administration and post-treatment of DM could both attenuate nicotine withdrawal signs. Moreover, DM could suppress nicotine-induced behavioral sensitization. Neurochemical experiments show that co-administration and post-treatment of DM abolished nicotine-induced increase of the DA turnover rate in the mPFC, but not in the NAc and DS. Conclusions The results suggest that DM has a great therapeutic potential in the treatment of nicotine dependence. Implications Our results showed that DM could suppress nicotine-induced rewarding effect and drug-seeking-related behavior. In addition, co-administration and post-treatment of DM could both attenuate nicotine withdrawal signs. Moreover, DM could suppress nicotine-induced behavioral sensitization. Neurochemical experiments show that co-administration and post-treatment of DM abolished nicotine-induced increase of the DA turnover rate in the mPFC, but not in the NAc and DS. These results suggest that DM has a great therapeutic potential in the treatment of nicotine dependence.