Effects and potential mechanisms of action of disulfiram and nepicastat on morphine dependence in experimental animals

In recent years, disulfiram (DSF) has been found to be effective in the treatment of cocaine dependence, which is likely to be caused by blocking the activity of dopamine beta-hydroxylase (DBH). A compound that is a selective DBH inhibitor is nepicastat. The results of preclinical studies indicate that nepicastat is also effective in reducing symptoms of cocaine dependence. Unfortunately, there are no data in the literature on the effect of DSF and nepicastat on the addictive effects of opioids and the development of tolerance. The aim of the current project is to evaluate the effects of DSF and nepicastat on the development of physical and mental dependence after repeated morphine administration, as well as the development of tolerance to the analgesic effect of morphine. It is also planned to investigate the mechanisms involved in the action of DSF and nepicastat, with particular emphasis on the role of DBH and glutamate receptors. The following research hypotheses were made: (1) DSF and nepikastat moderate the development of the physical morphine dependence; (2) DSF and nepikastat ameliorate the development of tolerance to the analgesic effect of morphine; (3) DSF and nepikastat ameliorate the development of psychological morphine dependence; (4) The mechanism of action of DSF and nepicastat is related to its effect on DBH activity and / or glataminergic receptors. The following research methods will be used in individual stages of the research: I. Research on physical dependence - evaluation of withdrawal symptoms. The influence of DSF and nepicastat on the development of physical dependence after administration of morphine will be verified by assessing the severity of withdrawal symptoms caused by naloxone administration. II. Study of the effect of DSF and nepicastat on the development of tolerance to the analgesic effect of morphine in behavioral models. In order to assess the tolerance to the analgesic effect of morphine and to verify the influence of the tested substances on its development, an acute pain model will be used. The analgesic effect will be assessed by measuring the sensory threshold of a mechanical stimulus according to the modification of the Randall-Selitto method, as well as measuring the threshold of thermal sensation in the tail-flick test. III. Study of the rewarding and motivational properties of morphine and the relapse to its exploratory behavior. The study will use a model of intravenous self-administration of morphine. To evaluate the effect of DSF / nepicastat on extinction / recurrence of morphine-seeking behavior, test compounds will be administered repeatedly during the morphine withdrawal period or once (in three selected doses) during the relapse phase induced by an unconditional (morphine) or conditional (light + the sound associated with its self-administration). IV. Neurochemical and molecular studies. To explain the mechanisms of DSF and nepicastat action, neurochemical procedures (in vivo microdialysis and analysis of DA and glutamate concentrations using HPLC method) and molecular procedures (analysis of glutamate receptor proteins and DBH protein expression in selected brain structures by Western blot method) will be used. All the above-mentioned methods are internationally recognized research methodologies under the relevant circumstances. The proposed research leads to the generation of new knowledge about the molecular basis of addictions. Understanding the mechanism of action of DSF may be helpful in the development of new drugs against addiction. Opioid dependence continues to be a serious medical and socio-economic problem on a global scale, and effective drugs are not available. The large size of the population affected by opioid dependence, along with treatment deficiencies, also leads to significant economic losses. Therefore, undertaking planned research is also justified by socio-economic reasons.