Effects of persistent cocaine self-administration on amygdala-dependent and dorsal striatum-dependent learning in rats

GSK3β Activity in Reward Circuit Functioning and Addiction

Glycogen synthase kinase-3β (GSK3β), primarily described as a regulator of glycogen metabolism, is a molecular hub linking numerous signaling pathways and regulates many cellular processes like cytoskeletal rearrangement, cell migration, apoptosis, and proliferation. In neurons, the kinase is engaged in molecular events related to the strengthening and weakening of synapses, which is a subcellular manifestation of neuroplasticity. Dysregulation of GSK3β activity has been reported in many neuropsychiatric conditions, like schizophrenia, major depressive disorder, bipolar disorder, and Alzheimer’s disease. In this review, we describe the kinase action in reward circuit-related structures in health and disease. The effect of pharmaceuticals used in the treatment of addiction in the context of GSK3β activity is also discussed.

3D Synaptic Organization of the Rat CA1 and Alterations Induced by Cocaine Self-Administration

The hippocampus plays a key role in contextual conditioning and has been proposed as an important component of the cocaine addiction brain circuit. To gain knowledge about cocaine-induced alterations in this circuit, we used focused ion beam milling/scanning electron microscopy to reveal and quantify the three-dimensional synaptic organization of the neuropil of the stratum radiatum of the rat CA1, under normal circumstances and after cocaine-self administration (SA). Most synapses are asymmetric (excitatory), macular-shaped, and in contact with dendritic spine heads. After cocaine-SA, the size and the complexity of the shape of both asymmetric and symmetric (inhibitory) synapses increased but no changes were observed in the synaptic density. This work constitutes the first detailed report on the 3D synaptic organization in the stratum radiatum of the CA1 field of cocaine-SA rats. Our data contribute to the elucidation of the normal and altered synaptic organization of the hippocampus, which is crucial for better understanding the neurobiological mechanisms underlying cocaine addiction.

Adolescent-onset vs. adult-onset cocaine use: Impact on cognitive functioning in animal models and opportunities for translation

Animal models are poised to make key contributions to the study of cognitive deficits associated with chronic cocaine use in people. Advantages of animal models include use of a longitudinal experimental design that can control for drug use history and onset-age, sex, drug consumption, and abstinence duration. Twenty-two studies were reviewed (13 in adult male rats, 5 in adolescent vs. adult male rats, 3 in adult male monkeys, and 1 in adult female monkeys), and it was demonstrated repeatedly that male animals with adult-onset cocaine self-administration exposure had impairments in sustained attention, decision making, stimulus-reward learning, working memory, and cognitive flexibility, but not habit learning and spatial learning and memory. These findings have translational relevance because adult cocaine users exhibit a similar range of cognitive deficits. In the limited number of studies available, male rats self-administering cocaine during adolescence were less susceptible than adults to impairment in cognitive flexibility, stimulus-reward learning, and decision making, but were more susceptible than adults to impairment in working memory, a finding also reported in the few studies performed in early-onset cocaine users. These findings suggest that animal models can help fill an unmet need for investigating important but yet-to-be-fully-addressed research questions in people. Research priorities include further investigation of differences between adolescents and adults as well as between males and females following chronic cocaine self-administration. A comprehensive understanding of the broad range of cognitive consequences of chronic cocaine use and the role of developmental plasticity can be of value for improving neuropsychological recovery efforts.

Hippocampal BDNF regulates a shift from flexible, goal-directed to habit memory system function following cocaine abstinence

The transition from recreational drug use to addiction involves pathological learning processes that support a persistent shift from flexible, goal-directed to habit behavioral control. Here, we examined the molecular mechanisms supporting altered function in hippocampal (HPC) and dorsolateral striatum (DLS) memory systems following abstinence from repeated cocaine. After 3 weeks of cocaine abstinence (experimenter- or self-administered), we tested new behavioral learning in male rats using a dual-solution maze task, which provides an unbiased approach to assess HPC- versus DLS-dependent learning strategies. Dorsal hippocampus (dHPC) and DLS brain tissues were collected after memory testing to identify transcriptional adaptations associated with cocaine-induced shifts in behavioral learning. Our results demonstrate that following prolonged cocaine abstinence rats show a bias toward the use of an inflexible, habit memory system (DLS) in lieu of a more flexible, easily updated memory system involving the HPC. This memory system bias was associated with upregulation and downregulation of brain-derived neurotrophic factor (BDNF) gene expression and transcriptionally permissive histone acetylation (acetylated histone H3, AcH3) in the DLS and dHPC, respectively. Using viral-mediated gene transfer, we overexpressed BDNF in the dHPC during cocaine abstinence and new maze learning. This manipulation restored HPC-dependent behavioral control. These findings provide a system-level understanding of altered plasticity and behavioral learning following cocaine abstinence and inform mechanisms mediating the organization of learning and memory more broadly.

Memory Systems and the Addicted Brain

The view that anatomically distinct memory systems differentially contribute to the development of drug addiction and relapse has received extensive support. The present brief review revisits this hypothesis as it was originally proposed 20 years ago (1) and highlights several recent developments. Extensive research employing a variety of animal learning paradigms indicates that dissociable neural systems mediate distinct types of learning and memory. Each memory system potentially contributes unique components to the learned behavior supporting drug addiction and relapse. In particular, the shift from recreational drug use to compulsive drug abuse may reflect a neuroanatomical shift from cognitive control of behavior mediated by the hippocampus/dorsomedial striatum toward habitual control of behavior mediated by the dorsolateral striatum (DLS). In addition, stress/anxiety may constitute a cofactor that facilitates DLS-dependent memory, and this may serve as a neurobehavioral mechanism underlying the increased drug use and relapse in humans following stressful life events. Evidence supporting the multiple systems view of drug addiction comes predominantly from studies of learning and memory that have employed as reinforcers addictive substances often considered within the context of drug addiction research, including cocaine, alcohol, and amphetamines. In addition, recent evidence suggests that the memory systems approach may also be helpful for understanding topical sources of addiction that reflect emerging health concerns, including marijuana use, high-fat diet, and video game playing.

SIV/macaque model of HIV infection in cocaine users: minimal effects of cocaine on behavior, virus replication, and CNS inflammation

Studies of the effects of drugs of abuse on HIV immune status, disease progression, and neuroAIDS have produced conflicting data and have not definitively shown whether this combination promotes cognitive impairment or disease progression. Using a consistent SIV-macaque model, we investigated the effects of cocaine on behavior, virologic parameters, and CNS inflammation. Macaques received either vehicle or chronic administration of behaviorally active doses of cocaine (1.7 or 3.2 mg/kg/day). Chronic cocaine administration reduced CD8+ T cell counts during acute and late stage infection but had no effect on CD4+ T cell counts. Low-dose cocaine-treated animals had lower CSF vRNA levels late in infection, but cocaine did not alter plasma viral load or vRNA or protein in brain. There were no differences in CSF CCL-2 or interleukin (IL)-6 levels or severity of encephalitis in cocaine-treated as compared to vehicle-treated macaques. There were no differences in brain inflammation or neurodegeneration markers, as determined by interferon (IFN)-β, MxA, CCL2, IL-6, TNFα, IFNγ, and indolamine 2,3-deoxygenase mRNA levels. APP levels also were not altered. The executive function of inhibitory control was not impaired in cocaine-treated or control animals following SIV infection. However, animals receiving 3.2 mg/kg/day cocaine performed more slowly in a bimanual motor test. Thus, chronic administration of cocaine produced only minor changes in behavior, encephalitis severity, CNS inflammation/neurodegeneration, and virus replication in SIV-infected pigtailed macaques, suggesting that cocaine would have only modest effects on the progression of neuroAIDS in HIV-infected individuals.

Cognitive enhancers for facilitating drug cue extinction: insights from animal models

Given the success of cue exposure (extinction) therapy combined with a cognitive enhancer for reducing anxiety, it is anticipated that this approach will prove more efficacious than exposure therapy alone in preventing relapse in individuals with substance use disorders. Several factors may undermine the efficacy of exposure therapy for substance use disorders, but we suspect that neurocognitive impairments associated with chronic drug use are an important contributing factor. Numerous insights on these issues are gained from research using animal models of addiction. In this review, the relationship between brain sites whose learning, memory and executive functions are impaired by chronic drug use and brain sites that are important for effective drug cue extinction learning is explored first. This is followed by an overview of animal research showing improved treatment outcome for drug addiction (e.g. alcohol, amphetamine, cocaine, heroin) when explicit extinction training is conducted in combination with acute dosing of a cognitive-enhancing drug. The mechanism by which cognitive enhancers are thought to exert their benefits is by facilitating consolidation of drug cue extinction memory after activation of glutamatergic receptors. Based on the encouraging work in animals, factors that may be important for the treatment of drug addiction are considered.

Effects of self-administered cocaine in adolescent and adult male rats on orbitofrontal cortex-related neurocognitive functioning

RATIONALE

Deficits in amygdala-related stimulus-reward learning are produced following 18 drug-free days of cocaine self-administration or its passive delivery in rats exposed during adulthood. No deficits in stimulus-reward learning are produced by cocaine exposure initiated during adolescence.

OBJECTIVES

To determine if age of initiating cocaine exposure differentially affects behavioral functioning of an additional memory system linked to cocaine addiction, the orbitofrontal cortex.

MATERIALS AND METHODS

A yoked-triad design (n = 8) was used. One rat controlled cocaine delivery and the other two passively received cocaine or saline. Rats controlling drug delivery (1.0 mg/kg) self-administered cocaine from either P37-P59 or P77-P99, and then underwent 18 drug-free days (P60-P77 vs. P100-P117). Rats next were tested for acquisition of odor-delayed win-shift behavior conducted over 15 sessions (P78-P96 vs. P118-P136).

RESULTS

Cocaine self-administration did not differ between adults and adolescents. During the test phase of the odor-delayed win-shift task (relatively difficult task demands), rats from both drug-onset ages showed learning deficits. Rats with cocaine self-administration experience committed more errors and had longer session latencies compared to rats passively receiving saline or cocaine. Rats with adolescent-onset cocaine self-administration experience showed an additional learning deficit by requiring more sessions to reach criterion levels for task acquisition compared to same-aged passive saline controls or rats with adult-onset cocaine self-administration experience. Rats passively receiving cocaine did not differ from the passive saline control from either age group.

CONCLUSIONS

Rats with adolescent-onset cocaine self-administration experience were more impaired in an orbitofrontal cortex-related learning task than rats with adult-onset cocaine self-administration experience.

Feeding-elicited cataplexy in orexin knockout mice

Mice lacking orexin/hypocretin signaling have sudden episodes of atonia and paralysis during active wakefulness. These events strongly resemble cataplexy, episodes of sudden muscle weakness triggered by strong positive emotions in people with narcolepsy, but it remains unknown whether murine cataplexy is triggered by positive emotions. To determine whether positive emotions elicit murine cataplexy, we placed orexin knockout (KO) mice on a scheduled feeding protocol with regular or highly palatable food. Baseline sleep/wake behavior was recorded with ad libitum regular chow. Mice were then placed on a scheduled feeding protocol in which they received 60% of their normal amount of chow 3 h after dark onset for the next 10 days. Wild-type and KO mice rapidly entrained to scheduled feeding with regular chow, with more wake and locomotor activity prior to the feeding time. On day 10 of scheduled feeding, orexin KO mice had slightly more cataplexy during the food-anticipation period and more cataplexy in the second half of the dark period, when they may have been foraging for residual food. To test whether more palatable food increases cataplexy, mice were then switched to scheduled feeding with an isocaloric amount of Froot Loops, a food often used as a reward in behavioral studies. With this highly palatable food, orexin KO mice had much more cataplexy during the food-anticipation period and throughout the dark period. The increase in cataplexy with scheduled feeding, especially with highly palatable food, suggests that positive emotions may trigger cataplexy in mice, just as in people with narcolepsy. Establishing this connection helps validate orexin KO mice as an excellent model of human narcolepsy and provides an opportunity to better understand the mechanisms that trigger cataplexy.

Dissociable effects of cocaine-seeking behavior following D1 receptor activation and blockade within the caudal and rostral basolateral amygdala in rats

Research with dopamine D(1) receptor antagonists or neuronal inactivating agents suggests that there is dissociable regulation of cocaine-seeking behavior by the rostral and caudal basolateral amygdala. In the present study, discrete infusions of the D(1) receptor agonist SKF 81297 (0.0-0.8 microg per side) were compared with those of the D(1) receptor antagonist SCH 23390 (0.0-2.0 microg per side) to demonstrate directly the importance of D(1) receptor mechanisms within the rostral and caudal basolateral amygdala for their functional heterogeneity in regulating cocaine-seeking behavior. Under a second-order schedule, cocaine-seeking behavior was studied during maintenance (cocaine and cocaine cues present) and reinstatement (only cocaine cues present). Food-maintained responding was used to examine the specificity of maximal behaviorally effective doses of SKF 81297 and SCH 23390. The results demonstrated that the D(1) agonist (0.4 or 0.8 microg) increased and the D(1) antagonist (1.0 microg) decreased cocaine-seeking behavior during maintenance when infused into the caudal but not the rostral basolateral amygdala. Cocaine intake was not affected by the agonist, and was decreased by the antagonist. During reinstatement, the D(1) agonist (0.4 microg) increased and the D(1) antagonist (1.0 microg) decreased cocaine-seeking behavior when infused into the rostral but not the caudal basolateral amygdala. In tests for behavioral specificity, the above effective doses of SKF 81297 and SCH 23390 used in self-administration experiments did not alter food-maintained responding. However, the 2.0-microg dose of SCH 23390 suppressed drug-maintained and food-maintained responding after infusion into both subregions. Collectively, these findings indicate dissociable sensitivity to D(1) receptor ligands within the caudal and rostral basolateral amygdala for altering cocaine-seeking behavior under different conditions that model phases of addiction.

Role of the orbitofrontal cortex and dorsal striatum in regulating the dose-related effects of self-administered cocaine

Little is known regarding which neural systems regulate dose-related changes in responses maintained by self-administered cocaine. This empirical question is important because elucidating neural systems engaged in this process could provide clues for effectively treating cocaine addiction. It has been suggested that different cocaine doses represent reinforcers of differing magnitudes, implicating the dorsal striatum or orbitofrontal cortex as important. Rats were trained to self-administer 1.0 mg/kg cocaine under a fixed-interval based second-order schedule. Next, cocaine unit doses (0.1-3.0 mg/kg) were each non-systematically available for a 5-day block of sessions. Tests (1h) were conducted on day 3 (vehicle) and day 5 (100 microg lidocaine) of each block. Lidocaine inactivation of the lateral dorsal striatum had no effect on dose-related responding or cocaine intake. In contrast, when doses along the ascending limb were available for self-administration, lidocaine inactivation of the lateral orbitofrontal cortex caused reductions in responding and cocaine intake, resulting in overall flattening of dose-response curves. This included reductions during the entire 1-h test sessions and during the interval immediately following the first cocaine infusion of test sessions. Lidocaine inactivation of the lateral orbitofrontal cortex did not alter responding during the first cocaine-free interval of test sessions, but increased the latency to the first infusion. Collectively, the findings suggest that when the amount of experience with different cocaine unit doses is limited to a few sessions, the lateral orbitofrontal cortex regulates the dose-related effects of self-administered cocaine, likely by processing information pertaining to the reinforcing value of each unit dose.

Cocaine self-administration improves performance in a highly demanding water maze task

RATIONALE

Long-term potentiation (LTP) is considered to be a cellular substrate of learning and memory. Indeed, the involvement of LTP-like mechanisms in spatial learning has consistently been demonstrated in the Morris water maze test. We have previously shown that hippocampal LTP in Lewis rats was modulated by cocaine self-administration, although the performance of cocaine-self-administered rats in the Morris water maze was not altered.

OBJECTIVE

Given that the ease of the task previously used could have masked any possible effects of the cocaine-induced LTP enhancement on spatial learning, a new and more difficult water maze task was devised to address this issue.

MATERIALS AND METHODS

Animals self-administered cocaine (1 mg/kg) or saline under a fixed ratio 1 schedule of reinforcement for 22 days. Spatial learning was assessed in a difficult water maze task (four sessions, two trials per session with a 90-min intertrial interval), and spatial memory was also evaluated 48 h after training (a 90-s test). Additionally, reversal learning and perseverance were also studied.

RESULTS

There was a reduced latency in finding the hidden platform during training, as well as improved memory of the platform location in cocaine-self-administered rats with respect to animals that self-administered saline. No differences were observed in reversal learning or perseverance between groups.

CONCLUSIONS

Our data suggest that cocaine self-administration facilitates learning and memory in the water maze test only when animals are submitted to highly demanding tasks, involving working memory or consolidation-like processes during the intertrial interval.

Differential effects of self-administered cocaine in adolescent and adult rats on stimulus-reward learning

RATIONALE

Adult cocaine addicts, abstinent at the time of testing, show a variety of neurocognitive impairments. Less clear is whether there are differences in the degree of impairment if cocaine use is initiated during adolescence rather than adulthood.

OBJECTIVES

Using a preclinical model, we evaluated if stimulus-reward learning was impacted differently in rats exposed to cocaine during adolescence (beginning on postnatal day 37) vs adulthood (beginning on postnatal days 74-79) and then tested after a drug-free period.

MATERIALS AND METHODS

A yoked-triad design of intravenous cocaine self-administration in adult (n = 8 triads) and adolescent (n = 8 triads) rats was used. Sets of three animals either contingently self-administered cocaine or received cocaine or saline in a noncontingent manner. Rats self-administering 1-mg/kg doses of cocaine responded under a fixed-ratio 5, timeout 20-s schedule of reinforcement. After 18 2-h drug or saline sessions, all rats (now adults) began the drug-free period in their home environments. Testing in a stimulus-reward learning task (conditioned cue preference) began 19 days later.

RESULTS

Self-administration behavior was similar in adolescent and adult rats. Lever responses were not significantly different, and both age groups averaged approximately 20 infusions per session. Rats contingently self-administering cocaine or passively exposed to cocaine during adulthood showed stimulus-reward learning deficits in the conditioned cue preference task. Rats exposed to contingent or noncontingent cocaine during adolescence had normal learning, showing strong preferences for a Froot Loops-paired cue.

CONCLUSIONS

These findings suggest that adolescents are insensitive to cocaine-induced impairment of learning related to amygdala memory system functioning.

Influence of sex, estrous cycle, and drug-onset age on cocaine self-administration in rats (Rattus norvegicus)

The influence of sex, phase of the estrous cycle, and age of drug onset on cocaine self-administration was examined. Adult male, adult female, and adolescent male rats (Rattus norvegicus) were evaluated using low fixed-ratio (FR) schedules of drug delivery with a single fixed cocaine unit dose or a range of cocaine unit doses with a single FR schedule. Sex differences in adults were observed for mg/kg consumption of the 3.0-mg/kg unit dose, with consumption being significantly less in estrus females than in males. Over the estrous cycle, mg/kg consumption of this unit dose was significantly less during estrus than during metestrus-diestrus. Differences due to age of drug onset were also observed, with mg/kg consumption of the 3.0-mg/kg unit dose being significantly less in adolescent males than adult males or adult females during metestrus-diestrus. In contrast, these various groups did not have significantly different mg/kg intakes of cocaine unit doses <3.0 mg/kg, nor did they significantly differ in the rates and patterns of responding and number of infusions earned as a function of FR schedule or unit dose of cocaine available. The role of sex, estrus cycle, and drug-onset age on cocaine self-administration appears to be minimal under these experimental conditions. Experimental conditions that favor no sex or age differences in cocaine intake (1.0-mg/kg unit dose and low FR) may be useful for evaluating potential sex or age differences in the consequences of cocaine self-administration more reliably, as cocaine intake would not be an uncontrolled factor.

Cocaine and Pavlovian fear conditioning: dose-effect analysis

Emerging evidence suggests that cocaine and other drugs of abuse can interfere with many aspects of cognitive functioning. The authors examined the effects of 0.1-15mg/kg of cocaine on Pavlovian contextual and cued fear conditioning in mice. As expected, pre-training cocaine dose-dependently produced hyperactivity and disrupted freezing. Surprisingly, when the mice were tested off-drug later, the group pre-treated with a moderate dose of cocaine (15mg/kg) displayed significantly less contextual and cued memory, compared to saline control animals. Conversely, mice pre-treated with a very low dose of cocaine (0.1mg/kg) showed significantly enhanced fear memory for both context and tone, compared to controls. These results were not due to cocaine's anesthetic effects, as shock reactivity was unaffected by cocaine. The data suggest that despite cocaine's reputation as a performance-enhancing and anxiogenic drug, this effect is seen only at very low doses, whereas a moderate dose disrupts hippocampus and amygdala-dependent fear conditioning.

Cocaine self-administration selectively abolishes LTD in the core of the nucleus accumbens

The core and shell of the nucleus accumbens have critical, differential roles in drug-dependent behaviors. Here we show that operant cocaine self-administration inhibits long-term depression (LTD) in both structures after 1 d of abstinence. However, after 21 d of abstinence, LTD was abolished exclusively in the nucleus accumbens core of cocaine self-administering rats, suggesting that voluntary cocaine self-administration induced long-lasting neuroadaptations in the core that could underlie drug-seeking behavior and relapse.

Influence of cocaine self-administration on learning related to prefrontal cortex or hippocampus functioning in rats

RATIONALE

Individuals who abuse cocaine have cognitive deficits, particularly in functions associated with the orbitofrontal cortex. It is not clear to what extent the impact of cocaine on cognitive functioning is related to its role as a behavioral reinforcer. A preclinical means to investigate this issue is to use a yoked-triad procedure in which sets of three animals either contingently self-administer cocaine or receive passive administration of cocaine or saline in a noncontingent manner.

OBJECTIVE

Using this procedure, we assessed cocaine's effect on learning that requires a functionally intact prefrontal cortex (prelimbic or insular/orbital subregions) or hippocampus.

METHODS

Rats self-administering 1-mg/kg unit doses of cocaine responded under a fixed-ratio 5, time-out 20-s schedule of drug delivery. Testing took place in a radial-arm maze within the first 30 min after 2-hr drug sessions ended, beginning after 2.5 months of cocaine or saline exposure.

RESULTS

Rats self-administering cocaine earned 14-18 infusions on average throughout different phases of the study. In groupwise comparisons, learning in the visually guided delayed win-shift (prelimbic prefrontal cortex-related) and win-shift (hippocampus-related) tasks was not influenced by contingent or noncontingent cocaine exposure. Session latency, though, was shorter in both cocaine-exposed groups during the win-shift task. During the odor-guided delayed win-shift task (insular/orbital prefrontal cortex-related), learning was disrupted in rats self-administering cocaine, with no influence of noncontingent cocaine exposure.

CONCLUSIONS

Based on these and previous findings, learning related to functioning of the insular/orbital prefrontal cortex and amygdala is the most consistently disrupted in cocaine-intoxicated rats after long-term drug exposure.

Cognitive sequelae of intravenous amphetamine self-administration in rats: evidence for selective effects on attentional performance

Characterizing the nature and severity of cognitive deficits associated with chronic stimulant abuse may provide new insights into the neural substrates of drug addiction because such deficits may contribute to the chronic relapsing nature of compulsive drug use. This investigation examines in rats the long-term cognitive consequences of intravenously self-administered amphetamine, specifically on performance of a 5-choice serial reaction time task (5-CSRTT), which assesses visuo-spatial attention and impulsivity. Rats experienced 5 days of intravenous (i.v.) amphetamine self-administration and were then withdrawn for a period of 9 days, during which time testing on the 5-CSRTT took place. This was repeated on five consecutive occasions for a period of 10 weeks. Controls experienced identical training on the 5-CSRTT but during the self-administration sessions received yoked i.v. infusions of normal saline. The results reveal a selective and reproducible pattern of deficits on the 5-CSRTT following repeated withdrawal from amphetamine self-administration, with deleterious effects on the speed and accuracy of responding as well as increased omission errors. Premature (impulsive) responding, perseveration, and food consumption latencies were not significantly affected. Deficits in attentional performance fully recovered 4-5 days after amphetamine cessation and there was no evidence of any long-term disturbances, even when the attentional load was increased. However, following a 2-month abstinence period, abnormalities in the subsequent effects of acute noncontingent amphetamine were found, with increased omissions, slower response times, and reduced impulsivity. Thus, contingent i.v. amphetamine administration has both short- and long-term consequences, which may be relevant to the complex disturbances that accompany drug addiction.

Cocaine makes actions insensitive to outcomes but not extinction: implications for altered orbitofrontal-amygdalar function

Addiction is characterized by persistent drug-seeking despite adverse consequences or outcomes. Such persistent behavior may result from drug-induced brain changes that increase the control of behavior by associations between antecedent cues and responses. However, it is equally plausible that brain changes cause a decrease in the control of behavior by the value of likely outcomes. To test whether drug exposure can cause persistent behavior, and to distinguish between these two accounts of such behavior, we tested cocaine-experienced rats in a Pavlovian 'reinforcer devaluation' task, which provides independent assessments of the control of behavior by antecedent cues and outcome representations. We found that cocaine exposure caused persistent responding in this setting a month after the last drug treatment, and that this deficit resulted from an inability to use representations of outcome value to guide behavior rather than from changes in stimulus-response learning or response inhibition.