Individual differences in cocaine-induced conditioned place preference in male rats: Behavioral and transcriptomic evidence.

BACKGROUND: Substance use disorder emerges in a small proportion of drug users and has the characteristics of a chronic relapsing pathology. AIMS: Our study aimed to demonstrate and characterize the variability in the expression of the rewarding effects of cocaine in the conditioned place preference (CPP) paradigm. METHODS: A cocaine-CPP paradigm in male Sprague-Dawley rats with an extinction period of 12 days and reinstatement was conducted. A statistical model was developed to distinguish rats expressing or not a cocaine-induced place preference. RESULTS: Two groups of rats were identified: rats that did express rewarding effects (CPP expression (CPPE), score >102 s) and rats that did not (no CPP expression (nCPPE), score between -85 and 59 s). These two groups did not show significant differences in a battery of behavioral tests. To identify differentially expressed genes in the CPPE and nCPPE groups, a whole-transcriptome ribonucleic acid-sequencing analysis was performed in the nucleus accumbens (NAc) 24 h after the CPP test. Four immediate early genes (Fos, Egr2, Nr4a1, and Zbtb37) were differentially expressed in the NAc of CPPE rats after expression of CPP. Variability in cocaine-induced place preference persisted in the CPPE and nCPPE groups after the extinction and reinstatement phases. Transcriptomic differences observed after reinstatement were distinct from those observed immediately after expression of CPP. CONCLUSION: These new findings provide insights into the identification of mechanisms underlying interindividual variability in the response to cocaine's rewarding effects.

Acute and chronic neurobehavioral effects of the designer drug and bath salt constituent 3,4-methylenedioxypyrovalerone in the rat.

BACKGROUND: The substantial increase in use of 3,4-methylenedioxypyrovalerone (MDPV), a popular recreational synthetic cathinone, has raised legitimate questions about its behavioral consequences and abuse liability. AIMS: The aim of this study was to study MDPV-induced neurobehavioral effects in the rat, using different paradigms traditionally developed to study drug-attributed addictive properties. METHODS: Different patterns of intraperitoneal 3 mg/kg MDPV administration were investigated. Consequences on rat horizontal locomotion and behavior of acute, intermittent (once daily dosing over 10 days), and binge (three-time daily dosing for 3 days) MDPV administration as well as challenge after 10 day MDPV withdrawal were studied. The dopamine receptor-D1 antagonist, SCH23390, was bilaterally infused in the nucleus accumbens to determine the role of D1-receptors in MDPV-related effects on the associative memory recall using the conditioned place preference paradigm. In addition, in a separate experience using western blot, we investigated the effects of chronic MDPV administration (four injections during 24 h) on ΔFosB expression in the nucleus accumbens, caudate putamen, and prefrontal cortex. RESULTS: Acute MDPV administration increased stereotypies and open arm entries in the elevated plus maze while SCH23390 abolished MDPV-induced enhancing effects on memory consolidation. Intermittent MDPV administration resulted in sensitization of MDPV-induced locomotor effects and tolerance during the following challenge. With binge MDPV administration, locomotor activity was not altered despite tolerance onset after challenge. SCH23390 abolished MDPV-induced conditioned place preference. Chronic MDPV administration induced ΔFosB accumulation in the nucleus accumbens, caudate putamen, and prefrontal cortex. CONCLUSIONS: Our findings clearly show that MDPV produces profound behavioral alterations mediated by the activation of the dopaminergic system similarly to other amphetamines.