Unconditioned and conditioned factors contribute to the 'reinstatement' of cocaine place conditioning following extinction in C57BL/6 mice.
ABSTRACT Relapse to drug use following prolonged periods of abstinence results, in part, from the ability of contextual cues paired previously with self-administered drug to elicit drug craving and -seeking behavior. Given the popularity of the mouse for the genetic analysis of drug-induced behaviors, a place conditioning model of drug-seeking behavior was used to examine the ability of cocaine (COC) to reinstate extinguished conditioned reward in mice. In a series of experiments, COC place conditioning was produced in male C57BL/6 (B6) mice by four pairings of COC (15 or 25 mg/kg, IP) with the non-preferred compartment of a two-compartment place conditioning apparatus. Following a post-conditioning test (Post-Test), place conditioning was extinguished by repeated testing. The mice were then challenged with one of five COC doses (0, 5, 10, 15 or 25 mg/kg, IP) and allowed free access to both environments. Following extinction, COC injections reinstated place conditioning to 100% or greater, relative to the Post-Test. In a control experiment, mice received either COC or SAL paired with non-preferred compartment and were then challenged with either COC (15 mg/kg, IP) or SAL on the Post-Test. COC-conditioned, but not SAL-conditioned, mice exhibited place conditioning when tested in a COC-free state. Interestingly, COC injection on the Post-Test elicited an increase in approach behavior in both SAL- and COC-conditioned mice and this increase was equivalent to that produced by COC conditioning alone. No direct relationships were observed between the magnitude of place conditioning and either COC-induced or -conditioned locomotor hyperactivity in the non-preferred compartment. Thus, at least two independent processes appear to underlie the ability of a COC injection to elicit approach behavior towards the non-preferred compartment of a biased place conditioning apparatus in mice-reactivation of the conditioned incentive motivational properties of COC-paired cues and elicitation of unconditioned behavioral disinhibition. One or both of these processes sensitizes with the passage of time, increasing the propensity of B6 mice to approach non-preferred environments upon COC re-administration.
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ABSTRACT: INTRODUCTION: Prior research indicates methylphenidate (MPH) and alcohol (ethanol, EtOH) interact to significantly affect responses humans and mice. The present studies tested the hypothesis that MPH and EtOH interact to potentiate ethanol-related behaviors in mice. METHODS: We used several behavioral tasks including: drug discrimination in MPH-trained and EtOH-trained mice, conditioned place preference (CPP), rota-rod and the parallel rod apparatus. We also used gas chromatographic methods to measure brain tissue levels of EtOH and the D- and L-isomers of MPH and the metabolite, ethylphenidate (EPH). RESULTS: In discrimination, EtOH (1 g/kg) produced a significant leftward shift in the MPH generalization curve (1-2 mg/kg) for MPH-trained mice, but no effects of MPH (0.625-1.25 mg/kg) on EtOH discrimination in EtOH-trained mice (0-2.5 g/kg) were observed. In CPP, the MPH (1.25 mg/kg) and EtOH (1.75 g/kg) combination significantly increased time on the drug paired side compared to vehicle (30.7 %), but this was similar to MPH (28.8 %) and EtOH (33.6 %). Footslip errors measured in a parallel rod apparatus indicated that the drug combination was very ataxic, with footslips increasing 29.5 % compared to EtOH. Finally, brain EtOH concentrations were not altered by 1.75 g/kg EtOH combined with 1.25 mg/kg MPH. However, EtOH significantly increased D-MPH and L-EPH without changing L-MPH brain concentrations. CONCLUSIONS: The enhanced behavioral effects when EtOH is combined with MPH are likely due to the selective increase in brain D-MPH concentrations. These studies are consistent with observations in humans of increased interoceptive awareness of the drug combination and provide new clinical perspectives regarding enhanced ataxic effects of this drug combination.Psychopharmacology 09/2012; · 4.06 Impact Factor
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ABSTRACT: We examined the effect of acute administration of the selective D(3) receptor antagonist SB277011A on morphine-triggered reactivation of cocaine-induced conditioned place preference (CPP) in adult male Sprague-Dawley rats. Repeated pairing of animals with 15 mg/kg i.p. of cocaine HCl or vehicle to cue-specific CPP chambers produced a significant CPP response compared to animals paired only with vehicle in both chambers. Expression of the CPP response to cocaine was then extinguished by repeatedly giving the animals vehicle injections in the cocaine-paired chambers. The magnitude of the CPP response after extinction was not significantly different from that of animals paired only with vehicle. Expression of the extinguished CPP response was reactivated by acute administration of 5 mg/kg i.p. of morphine but not by vehicle. Acute administration of 6 or 12 mg/kg i.p. (but not 3 mg/kg) of SB277011A significantly attenuated morphine-triggered reactivation of the cocaine-induced CPP. SB277011A itself (12 mg/kg i.p.) did not reactivate the extinguished CPP response. Overall, SB277011 decreases the incentive motivational actions of morphine. The present findings suggest that central D(3) dopamine receptors are involved in relapse to cocaine-seeking behavior that a final common neural mechanism exists to mediate the incentive motivational effects of psychostimulants and opiates, and that selective dopamine D(3) receptor antagonists constitute promising compounds for treating addiction. Synapse, 2013. © 2013 Wiley Periodicals, Inc.Synapse 02/2013; · 2.31 Impact Factor
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ABSTRACT: RATIONALE: Rats develop preferences for places associated with the immediate rewarding effects of cocaine and aversions for places paired with the drug's delayed negative effects. The motivation to seek cocaine should therefore depend upon the relative magnitude of these two opposing effects of the drug. OBJECTIVE: The current study tested this notion by assessing the relative persistence of the positive and negative associations formed between environmental cues and the immediate or delayed effects of cocaine. METHODS: Rats were administered 1.0 mg/kg intravenous cocaine and placed into a distinctive environment either immediately or 15-min after injection, alternating daily with pairings of a second environment with saline. After four drug-place and four saline-place pairings, rats were returned to their home cages for 1, 7, or 21 days after which a 15-min place preference test was conducted. In a second experiment, the effectiveness of a single reconditioning session (one drug-place and one saline-place pairing) to reactivate learned cocaine-place associations was assessed after 1 or 3 weeks of drug abstinence. RESULTS: Places associated with the immediate effects of cocaine were preferred (CPP), while places associated with the delayed effects of cocaine were avoided (CPA). The persistence of these effects differed with CPP remaining viable at 3 weeks of withdrawal, while CPA was no longer present after 1 week. Reconditioning with an additional cocaine-place pairing failed to reinstate the CPA. CONCLUSIONS: Cue-induced "relapse" of cocaine-seeking behavior may be fueled in part by an increased persistence of positive relative to negative associations with drug-paired stimuli.Psychopharmacology 04/2013; · 4.06 Impact Factor