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Synthetic cathinones, such as 3,4-methylenedioxypyrovalerone (MDPV), are recreational drugs of abuse often identified in 'bath salts' preparations. Humans report compulsive patterns of bath salts use, and previous work suggests that a subset of rats develop unusually high levels of MDPV self-administration. This study aims to test the hypothesis that high levels of impulsivity (e.g., inability to withhold responding for a sucrose reward) will predispose rats to high levels of MDPV self-administration relative to rats with lower levels of impulsivity. The 1-choice serial reaction time task (1-CSRTT) was used to assess impulsivity (i.e., premature responding) in 10 female and 10 male Sprague Dawley rats. Rats were then allowed to self-administer 0.032 mg/kg/inf MDPV or 0.32 mg/kg/inf cocaine, after which full dose-response curves for MDPV (0.001-0.1 mg/kg/inf) or cocaine (0.01-1 mg/kg/inf) were generated under a FR5 schedule of reinforcement. After a history of self-administering MDPV or cocaine, impulsivity was reassessed under the 1-CSRTT, prior to evaluating the acute effects of MDPV (0.032-0.32 mg/kg) or cocaine (0.1-1 mg/kg) on impulsivity. Level of impulsivity was not correlated with subsequent levels of either MDPV or cocaine self-administration, and level of drug self-administration was also not correlated with subsequent levels of impulsivity, although acute administration of MDPV and cocaine did increase premature responding. In failing to find direct relationships between either impulsivity and subsequent drug-taking behaviour, or drug-taking behaviour and subsequent assessments of impulsivity, these findings highlight the complexity inherent in the associations between impulsive behaviour and drug-taking behaviour in both animal models and humans. [ABSTRACT FROM AUTHOR]

Pain is a significant clinical problem, and there is a need for effective pharmacotherapies with fewer adverse effects than currently available drugs (e.g., mu opioid receptor agonists). Cannabinoid receptor agonists enhance the antinociceptive effects of mu opioid receptor agonists, but it remains unclear which drugs and in what proportion will yield the most effective and safest treatments. The antinociceptive effects of the mu opioid receptor agonists etorphine and morphine alone and in combination with the cannabinoid receptor agonists Δ 9 -THC and CP55940 were studied in male Sprague-Dawley rats (n = 16) using a warm water tail withdrawal procedure. The ratio of opioid to cannabinoid (3:1, 1:1, and 1:3) varied for each mixture. Drugs administered alone or as pairwise mixtures of an opioid and a cannabinoid dose-dependently increased tail withdrawal latency. Mixtures with morphine produced supra-additive (CP55940) and additive (Δ 9 -THC) effects, whereas mixtures with etorphine and either cannabinoid were sub-additive. The interactions were not different among ratios for a particular mixture. The nature of the interaction between opioids and cannabinoids with regard to antinociceptive effects varies with the particular drugs in the mixture, which can have implications for designing combination therapies for pain. [ABSTRACT FROM AUTHOR]