Ibudilast attenuates cocaine self-administration and prime- and cue-induced reinstatement of cocaine seeking in rats

Ibudilast is a non-selective phosphodiesterase (PDE) inhibitor and glial cell modulator which has shown great promise for the treatment of drug and alcohol use disorders in recent clinical studies. However, it is unknown whether and how ibudilast affects cocaine seeking behavior. Here we show that systemic administration of ibudilast dose-dependently reduced cocaine self-administration under fixed- and progressive-ratio reinforcement schedules in rats and shifted cocaine dose-response curves downward. In addition, ibudilast decreased cocaine prime- and cue-induced reinstatement of cocaine seeking. These results indicate that ibudilast was effective in reducing the reinforcing effects of cocaine and relapse to cocaine seeking. Chronic cocaine exposure induces cAMP-related neuroadaptations in the reward circuitry of the brain. To investigate potential mechanisms for ibudilast-induced attenuation of cocaine self-administration, we recorded from ventral tegmental area (VTA) dopamine neurons in ex vivo midbrain slices prepared from rats that had undergone saline and cocaine self-administration. We found cocaine self-administration led to a decrease in inhibitory postsynaptic currents (IPSCs), an increase in the AMPAR/NMDAR ratio, and an increase in the excitation to inhibition (E/I) ratio. Ibudilast pretreatments enhanced GABAergic inhibition and did not further change cocaine-induced potentiation of excitation, leading to normalization of the E/I ratio. Restoration of the balance between excitation and inhibition in VTA dopamine neurons may contribute to the attenuation of cocaine self-administration by ibudilast.

Inhibition of CSF1R, a receptor involved in microglia viability, alters behavioral and molecular changes induced by cocaine

Different data suggest that microglia may participate in the drug addiction process as these cells respond to neurochemical changes induced by the administration of these substances. In order to study the role of microglia in drug abuse, Swiss mice aged 8-9 weeks were treated with the CSF1R inhibitor PLX3397 (40 mg/kg, p.o.) and submitted to behavioral sensitization or conditioned place preference (CPP) induced by cocaine (15 mg/kg, i.p.). Thereafter, brains were used to evaluate the effects of CSF1R inhibition and cocaine administration on morphological, biochemical and molecular changes. CSF1R inhibition attenuated behavioral sensitization, reduced the number of Iba-1+ cells and increased ramification and lengths of the branches in the remaining microglia. Additionally, both cocaine and PLX3397 increased the cell body to total cell size ratio of Iba-1+ cells, as well as CD68+ and GFAP+ stained areas, suggesting an activated pattern of the glial cells. Besides, CSF1R inhibition increased CX3CL1 levels in the striatum, prefrontal cortex and hippocampus, as well as reduced CX3CR1 expression in the hippocampus. In this region, cocaine also reduced BDNF levels, an effect that was enhanced by CSF1R inhibition. In summary, our results suggest that microglia participate in the behavioral and molecular changes induced by cocaine. This study contributes to the understanding of the role of microglia in cocaine addiction.

Neural sensitivity to risk in adults with co-occurring HIV infection and cocaine use disorder

Persons with co-occurring HIV infection and cocaine use disorder tend to engage in riskier decision-making. However, the neural correlates of sensitivity to risk are not well-characterized in this population. The purpose of this study was to examine the neural interaction effects of HIV infection and cocaine use disorder to sensitivity to risk. The sample included 79 adults who differed on HIV status and cocaine use disorder. During functional magnetic resonance imaging (fMRI), participants completed a Wheel of Fortune (WoF) task that assessed neural activation in response to variations of monetary risk (i.e., lower probability of winning a larger reward). Across groups, neural activation to increasing risk was in cortical and subcortical regions similar to previous investigations using the WoF in nondrug-using populations. Our analyses showed that there was a synergistic effect between HIV infection and cocaine use in the left precuneus/posterior cingulate cortex and hippocampus, and right postcentral gyrus, lateral occipital cortex, cerebellum, and posterior parietal cortex. HIV+ individuals with cocaine use disorder displayed neural hyperactivation to increasing risk that was not observed in the other groups. These results support a synergistic effect of co-occurring HIV infection and cocaine dependence in neural processing of risk probability that may reflect compensation. Future studies can further investigate and validate how neural activation to increasing risk is associated with risk-taking behavior.

Alpha-synuclein is strategically positioned for afferent modulation of midbrain dopamine neurons and is essential for cocaine preference

Alpha-synuclein (α-syn) is an abundant neuroprotein elevated in cocaine addicts, linked to drug craving, and recruited to axon terminals undergoing glutamatergic plasticity - a proposed mechanism for substance abuse. However, little is known about normal α-syn function or how it contributes to substance abuse. We show that α-syn is critical for preference of hedonic stimuli and the cognitive flexibility needed to change behavioral strategies, functions that are altered with substance abuse. Electron microscopic analysis reveals changes in α-syn targeting of ventral tegmental area axon terminals that is dependent upon the duration of cocaine exposure. The dynamic changes in presynaptic α-syn position it to control neurotransmission and fine-tune the complex afferent inputs to dopamine neurons, potentially altering functional dopamine output. Cocaine also increases postsynaptic α-syn where it is needed for normal ALIX function, multivesicular body formation, and cocaine-induced exosome release indicating potentially similar α-syn actions for vesicle release pre- and post-synaptically.

The sigma-1 receptor as key common factor in cocaine and food-seeking behaviors

Addiction and eating disorders involve brain reward circuits. Binge eating predisposes to addictive behavior, while the cessation of exposure to drugs of abuse leads to reward activities, including intake of tasty foods. Cocaine use is associated with a decrease in food intake, with reversal after drug use is discontinued. Exciting new findings show that receptors for the 'hunger' hormone, ghrelin, directly interact with the sigma-1 receptor (σ1R), which is a target of cocaine. σ1Rs are key players in regulating dopaminergic neurotransmission and ghrelin-mediated actions. This review focuses on the σ1 receptor as a general neuroendocrine regulator by directly interacting with neuronal G-protein-coupled receptors. This review also covers the early mechanisms by which cocaine binding to σ1 blocks the food-seeking behavior triggered by ghrelin. Those findings appear as fundamental to understand common mechanisms in drug addiction and eating disorders.

Cocaine-Induced Reinstatement of Cocaine Seeking Provokes Changes in the Endocannabinoid and N-Acylethanolamine Levels in Rat Brain Structures

There is strong support for the role of the endocannabinoid system and the noncannabinoid lipid signaling molecules, N-acylethanolamines (NAEs), in cocaine reward and withdrawal. In the latest study, we investigated the changes in the levels of the above molecules and expression of cannabinoid receptors (CB1 and CB2) in several brain regions during cocaine-induced reinstatement in rats. By using intravenous cocaine self-administration and extinction procedures linked with yoked triad controls, we found that a priming dose of cocaine (10 mg/kg, i.p.) evoked an increase of the anadamide (AEA) level in the hippocampus and prefrontal cortex only in animals that had previously self-administered cocaine. In the same animals, the level of 2-arachidonoylglycerol (2-AG) increased in the hippocampus and nucleus accumbens. Moreover, the drug-induced relapse resulted in a potent increase in NAEs levels in the cortical areas and striatum and, at the same time, a decrease in the tissue levels of oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) was noted in the nucleus accumbens, cerebellum, and/or hippocampus. At the level of cannabinoid receptors, a priming dose of cocaine evoked either upregulation of the CB1 and CB2 receptors in the prefrontal cortex and lateral septal nuclei or downregulation of the CB1 receptors in the ventral tegmental area. In the medial globus pallidus we observed the upregulation of the CB2 receptor only after yoked chronic cocaine treatment. Our findings support that in the rat brain, the endocannabinoid system and NAEs are involved in cocaine induced-reinstatement where these molecules changed in a region-specific manner and may represent brain molecular signatures for the development of new treatments for cocaine addiction.

Levamisole-induced vasculopathy with gastric involvement in a cocaine user

Reports of levamisole-induced vasculopathy (LIV) secondary to use of levamisole-contaminated cocaine largely have been limited to the skin. We report the case of a 35-year-old woman with painful purpuric lesions affecting the cheeks, nose, ears, arms, and legs of several days' duration. She recently had used crack cocaine. A biopsy of a lesion on the right arm demonstrated leukocytoclastic vasculitis. She also reported abdominal pain and gastric reflux of recent onset but denied any history of gastrointestinal tract disease. An upper gastrointestinal endoscopy was performed and demonstrated hemorrhagic erosions of the esophagus and stomach similar in appearance to the cutaneous lesions. Because dermatologists often are the specialists making the diagnosis of LIV, it is important they inform other involved clinicians that the skin may not be the sole repository of vascular insult.

Locomotor sensitization to cocaine in adolescent and adult female Wistar rats

Adolescent stress exposure is a risk factor for drug abuse, and sex differences contribute to psychostimulant responses. Although many studies have utilized the Wistar rat strain in adolescent stress paradigms, the impact of adolescent stress exposure on addiction-like outcomes has not been rigorously tested in female Wistar rats. In this study, locomotor sensitization was assessed in adolescent and adult female Wistar rats following either chronic stress during adolescence (CAS) or no stress (NS). Adolescent, but not adult, female Wistar rats developed locomotor sensitization to 15 mg/kg cocaine over 5 days of treatment, regardless of stress history. CAS reduced the initial locomotor response to novelty in both adolescent and adult rats compared to NS controls but had no effect on locomotor sensitization to cocaine in adolescents or adult female rats. These studies expand our understanding of age and adolescent stress on cocaine-induced behavioral plasticity in female Wistar rats.

Methyl supplementation attenuates cocaine-seeking behaviors and cocaine-induced c-Fos activation in a DNA methylation-dependent manner

Epigenetic mechanisms, such as histone modifications, regulate responsiveness to drugs of abuse, such as cocaine, but relatively little is known about the regulation of addictive-like behaviors by DNA methylation. To investigate the influence of DNA methylation on the locomotor-activating effects of cocaine and on drug-seeking behavior, rats receiving methyl supplementation via chronic l-methionine (MET) underwent either a sensitization regimen of intermittent cocaine injections or intravenous self-administration of cocaine, followed by cue-induced and drug-primed reinstatement. MET blocked sensitization to the locomotor-activating effects of cocaine and attenuated drug-primed reinstatement, with no effect on cue-induced reinstatement or sucrose self-administration and reinstatement. Furthermore, upregulation of DNA methyltransferase 3a and 3b and global DNA hypomethylation were observed in the nucleus accumbens core (NAc), but not in the medial prefrontal cortex (mPFC), of cocaine-pretreated rats. Glutamatergic projections from the mPFC to the NAc are critically involved in the regulation of cocaine-primed reinstatement, and activation of both brain regions is seen in human addicts when reexposed to the drug. When compared with vehicle-pretreated rats, the immediate early gene c-Fos (a marker of neuronal activation) was upregulated in the NAc and mPFC of cocaine-pretreated rats after cocaine-primed reinstatement, and chronic MET treatment blocked its induction in both regions. Cocaine-induced c-Fos expression in the NAc was associated with reduced methylation at CpG dinucleotides in the c-Fos gene promoter, effects reversed by MET treatment. Overall, these data suggest that drug-seeking behaviors are, in part, attributable to a DNA methylation-dependent process, likely occurring at specific gene loci (e.g., c-Fos) in the reward pathway.

Investigating the potential influence of cause of death and cocaine levels on the differential expression of genes associated with cocaine abuse

The development of new therapeutic strategies for the treatment of complex brain disorders such as drug addiction is likely to be advanced by a more complete understanding of the underlying molecular pathophysiology. Although the study of postmortem human brain represents a unique resource in this regard, it can be challenging to disentangle the relative contribution of chronic pathological processes versus perimortem events to the observed changes in gene expression. To begin to unravel this issue, we analyzed by quantitative PCR the midbrain expression of numerous candidate genes previously associated with cocaine abuse. Data obtained from chronic cocaine abusers (and matched control subjects) dying of gunshot wounds were compared with a prior study of subjects with deaths directly attributable to cocaine abuse. Most of the genes studied (i.e., tyrosine hydroxylase, dopamine transporter, forkhead box A2, histone variant H3 family 3B, nuclear factor kappa B inhibitor alpha, growth arrest and DNA damage-inducible beta) were found to be differentially expressed in chronic cocaine abusers irrespective of immediate cause of death or perimortem levels of cocaine, suggesting that these may represent core pathophysiological changes arising with chronic drug abuse. On the other hand, chemokine C-C motif ligand 2 and jun proto-oncogene expression were unaffected in cocaine-abusing subjects dying of gunshot wounds, in contrast to the differential expression previously reported in cocaine-related fatalities. The possible influence of cause of death and other factors on the cocaine-responsiveness of these genes is discussed.

Stress-induced cocaine seeking requires a beta-2 adrenergic receptor-regulated pathway from the ventral bed nucleus of the stria terminalis that regulates CRF actions in the ventral tegmental area

The ventral bed nucleus of the stria terminalis (vBNST) has been implicated in stress-induced cocaine use. Here we demonstrate that, in the vBNST, corticotropin releasing factor (CRF) is expressed in neurons that innervate the ventral tegmental area (VTA), a site where the CRF receptor antagonist antalarmin prevents the reinstatement of cocaine seeking by a stressor, intermittent footshock, following intravenous self-administration in rats. The vBNST receives dense noradrenergic innervation and expresses β adrenergic receptors (ARs). Footshock-induced reinstatement was prevented by bilateral intra-vBNST injection of the β-2 AR antagonist, ICI-118,551, but not the β-1 AR antagonist, betaxolol. Moreover, bilateral intra-vBNST injection of the β-2 AR agonist, clenbuterol, but not the β-1 agonist, dobutamine, reinstated cocaine seeking, suggesting that activation of vBNST β-2 AR is both necessary for stress-induced reinstatement and sufficient to induce cocaine seeking. The contribution of a β-2 AR-regulated vBNST-to-VTA pathway that releases CRF was investigated using a disconnection approach. Injection of ICI-118,551 into the vBNST in one hemisphere and antalarmin into the VTA of the contralateral hemisphere prevented footshock-induced reinstatement, whereas ipsilateral manipulations failed to attenuate stress-induced cocaine seeking, suggesting that β-2 AR regulate vBNST efferents that release CRF into the VTA, activating CRF receptors, and promoting cocaine use. Last, reinstatement by clenbuterol delivered bilaterally into the vBNST was prevented by bilateral vBNST pretreatment with antalarmin, indicating that β-2 AR-mediated actions in the vBNST also require local CRF receptor activation. Understanding the processes through which stress induces cocaine seeking should guide the development of new treatments for addiction.

Cardiac Fas-dependent and mitochondria-dependent apoptosis after chronic cocaine abuse

To evaluate whether chronic cocaine abuse will increase cardiac Fas-dependent and mitochondria-dependent apoptotic pathways, thirty-two male Wistar rats at 3–4 months of age were randomly divided into a vehicle-treated group (phosphate-buffered saline, PBS, 0.5 mL, SQ per day) and a cocaine-treated group (Cocaine, 10 mg/kg, SQ per day). After 3 months of treatment, the excised left ventricles were measured by H&E staining, Western blotting, DAPI staining and TUNEL assays. More cardiac TUNEL-positive apoptotic cells were observed in the Cocaine group than the PBS group. Protein levels of TNF-alpha, Fas ligand, Fas death receptor, FADD, activated caspase-8, and activated caspase-3 (Fas-dependent apoptosis) extracted from excised hearts in the Cocaine group were significantly increased, compared to the PBS group. Protein levels of cardiac Bax, cytosolic cytochrome c, t-Bid-to-Bid, Bak-to-Bcl-xL, Bax-to-Bcl-2 ratio, activated caspase-9, and activated caspase-3 (mitochondria-dependent apoptosis) were significantly increased in the Cocaine group, compared to the PBS group. Chronic cocaine exposure appeared to activate the cardiac Fas-dependent and mitochondria-dependent apoptosis, which may indicate a possible mechanism for the development of cardiac abnormalities in humans with chronic cocaine abuse.

Impact of pubertal and adult estradiol treatments on cocaine self-administration

Estradiol is thought to play a critical role in the increased vulnerability to psychostimulant abuse in women. Sex differences in the ability of estradiol to influence cocaine self-administration in adult rats have been hypothesized to depend upon pubertal estradiol exposure. The current study investigated whether the presence of gonadal hormones during puberty affected cocaine self-administration behavior and its sensitivity to adult estradiol treatment in male and female Sprague-Dawley rats. Subjects were gonadectomized or SHAM-operated at postnatal day (PD) 22, and received either OIL or estradiol benzoate (EB) during the approximate time of puberty (PD27 to PD37). Adult rats were subsequently treated with either EB or OIL 30 min before cocaine self-administration (0.3 mg/kg/inf) in order to examine the effects of pubertal manipulations on the estradiol sensitivity of acquisition on a fixed ratio (FR) 1 schedule, total intake on a FR5 schedule and motivation on a progressive ratio schedule. Adult EB treatment only affected cocaine self-administration in females, which is consistent with previous research. Adult EB treatment enhanced acquisition in all females irrespective of puberty manipulations. All females, except those treated with EB during puberty, displayed increased cocaine intake following adult EB treatment. Adult EB treatment only enhanced motivation in females that were intact during puberty, whereas those treated with EB during puberty showed reduced motivation. Therefore, the sensitivities of different self-administration behaviors to adult estradiol treatment are organized independently in females, with pubertal estradiol exerting a greater influence over motivational processes, and negligible effects on learning/acquisition.

Vasculopathy related to cocaine adulterated with levamisole: A review of the literature

BACKGROUND

Recently, there have been numerous case reports and series describing patients presenting with cutaneous vasculopathy that has been linked to the levamisole frequently found in cocaine.

OBJECTIVE

The purpose of this study was to review all published case reports and series of patients reported with cutaneous vasculopathic findings of lemavisole induced vasculopathy (LIV) associated with cocaine use.

METHODS

A review of PubMed was performed searching the keywords: levamisole, cocaine, in combination with vasculitis, and vasculopathy. Twenty-two case reports and series were available with sufficient data on reported patients to be included. Four patients from the authors' clinical experience are included as well.

RESULTS

A number of common clinical and pathological findings are reviewed, including lower extremity (46/55 patients, 84%) and ear involvement (40/55 patients, 73%), and positive anti-neutrophil cytoplasmic antibodies (ANCA) findings (p-ANCA 42/48 patients, 88%; anti human neutrophil elastase 11/11 patients, 100%). Similar numbers of patients were treated with systemic corticosteroids as were treated conservatively; there was comparable improvement on follow up.

CONCLUSIONS

There are a number of clinical and laboratory findings that are commonly found in patients with LIV. There is currently insufficient data to recommend treatment with systemic corticosteroids in patients with this condition.

Operant model of frustrated expected reward in mice

One aspect of the addictive process that has not been thoroughly investigated is the consequence of the frustrated state occurring when the drug is not available. The present study aimed to validate a novel operant model of frustrated expected reward in mice. C57BL/6J mice were trained in operant conditioning maintained by chocolate-flavoured pellets or cocaine. After the completion of high rates of responding on a progressive ratio schedule, the reward was unexpectedly withheld. The consequences of this frustrated behaviour on anxiety, aggressiveness, perseveration, extinction and reinstatement were investigated. Mice exposed to the frustrated event perseverated in the operant responses and showed increased aggressiveness in the resident-intruder test. These animals also showed higher rates of cue-induced reinstatement of drug seeking. The present study provides a reliable operant model in mice to evaluate a frustrated state following reward unavailability. This animal model could be useful to study the behavioural and neurochemical consequences related to the emotional states generated during the omission of a highly expected reward.

Subregion-specific role of glutamate receptors in the nucleus accumbens on drug context-induced reinstatement of cocaine-seeking behavior in rats

The functional integrity of the nucleus accumbens (NAC) core and shell is necessary for contextual cocaine-seeking behavior in the reinstatement animal model of drug relapse; however, the neuropharmacological mechanisms underlying this phenomenon are poorly understood. The present study evaluated the contribution of metabotropic glutamate receptor subtype 1 (mGluR1) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate receptor populations to drug context-induced reinstatement of cocaine-seeking behavior. Rats were trained to lever press for un-signaled cocaine infusions in a distinct context followed by extinction training in a different context. Cocaine-seeking behavior (non-reinforced active lever pressing) was then assessed in the previously cocaine-paired and extinction contexts after JNJ16259685 (mGluR1 antagonist: 0.0, 0.6, or 30 pg/0.3 µl/hemisphere) or CNQX (AMPA/kainate receptor antagonist: 0.0, 0.03, or 0.3 µg/0.3 µl /hemisphere) administration into the NAC core, medial or lateral NAC shell, or the ventral caudate-putamen (vCPu, anatomical control). JNJ16259685 or CNQX in the NAC core dose-dependently impaired contextual cocaine-seeking behavior relative to vehicle. Conversely, CNQX, but not JNJ16259685, in the lateral or medial NAC shell attenuated, whereas CNQX or JNJ16259685 in vCPu failed to inhibit, this behavior. The manipulations failed to alter instrumental behavior in the extinction context, general motor activity or food-reinforced instrumental behavior in control experiments. Thus, glutamate-mediated changes in drug context-induced motivation for cocaine involve distinct neuropharmacological mechanisms within the core and shell subregions of the NAC, with the stimulation of mGlu1 and AMPA/kainate receptors in the NAC core and the stimulation of AMPA/kainate, but not mGlu1, receptors in the NAC shell being necessary for this phenomenon.

[Relapse in cocaine addiction: a review]

Relapse remains a common problem in disorders related to cocaine use. The aim of this paper is to review recent research data on the variables and factors related to relapse in cocaine-dependent individuals. We carried out a systematic search for studies including variables related to cocaine use in some of the most important national and international databases: PubMed, ISI Web of Knowledge, The Cochrane Library, IME and ISOC. To locate the latest research data, the search covered the period January 2000 to July 2011. Many and varied factors and variables identified with some predictive power were identified, notably psychosocial problems, negative emotional states, anxiety, self-efficacy, psychopathological comorbidity, addictive severity, and several variables related to the treatment process. Knowledge about the relapse process has increased considerably in recent years, but although the influence of certain factors on relapse in cocaine use now seems clear, specific research is still scarce and inconclusive.

Probability and predictors of transition from first use to dependence on nicotine, alcohol, cannabis, and cocaine: results of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC)

BACKGROUND

This study aims to estimate general and racial-ethnic specific cumulative probability of developing dependence among nicotine, alcohol, cannabis or cocaine users, and to identify predictors of transition to substance dependence.

METHODS

Analyses were done for the subsample of lifetime nicotine (n=15,918), alcohol (n=28,907), cannabis (n=7389) or cocaine (n=2259) users who participated in the first and second wave of the National Epidemiological Survey on Alcohol and Related Conditions (NESARC). Discrete-time survival analyses were implemented to estimate the cumulative probability of transitioning from use to dependence and to identify predictors of transition to dependence.

RESULTS

The cumulative probability estimate of transition to dependence was 67.5% for nicotine users, 22.7% for alcohol users, 20.9% for cocaine users, and 8.9% for cannabis users. Half of the cases of dependence on nicotine, alcohol, cannabis and cocaine were observed approximately 27, 13, 5 and 4 years after use onset, respectively. Significant racial-ethnic differences were observed in the probability of transition to dependence across the four substances. Several predictors of dependence were common across the four substances assessed.

CONCLUSIONS

Transition from use to dependence was highest for nicotine users, followed by cocaine, alcohol and cannabis users. Transition to cannabis or cocaine dependence occurred faster than transition to nicotine or alcohol dependence. The existence of common predictors of transition dependence across substances suggests that shared mechanisms are involved. The increased risk of transition to dependence among individuals from minorities or those with psychiatric or dependence comorbidity highlights the importance of promoting outreach and treatment of these populations.

Direct involvement of sigma-1 receptors in the dopamine D1 receptor-mediated effects of cocaine

It is well known that cocaine blocks the dopamine transporter. This mechanism should lead to a general increase in dopaminergic neurotransmission, and yet dopamine D(1) receptors (D(1)Rs) play a more significant role in the behavioral effects of cocaine than the other dopamine receptor subtypes. Cocaine also binds to σ-1 receptors, the physiological role of which is largely unknown. In the present study, D(1)R and σ(1)R were found to heteromerize in transfected cells, where cocaine robustly potentiated D(1)R-mediated adenylyl cyclase activation, induced MAPK activation per se and counteracted MAPK activation induced by D(1)R stimulation in a dopamine transporter-independent and σ(1)R-dependent manner. Some of these effects were also demonstrated in murine striatal slices and were absent in σ(1)R KO mice, providing evidence for the existence of σ(1)R-D(1)R heteromers in the brain. Therefore, these results provide a molecular explanation for which D(1)R plays a more significant role in the behavioral effects of cocaine, through σ(1)R-D(1)R heteromerization, and provide a unique perspective toward understanding the molecular basis of cocaine addiction.

Mitochondrial impairment contributes to cocaine-induced cardiac dysfunction: Prevention by the targeted antioxidant MitoQ

The goal of this study was to assess mitochondrial function and ROS production in an experimental model of cocaine-induced cardiac dysfunction. We hypothesized that cocaine abuse may lead to altered mitochondrial function that in turn may cause left ventricular dysfunction. Seven days of cocaine administration to rats led to an increased oxygen consumption detected in cardiac fibers, specifically through complex I and complex III. ROS levels were increased, specifically in interfibrillar mitochondria. In parallel there was a decrease in ATP synthesis, whereas no difference was observed in subsarcolemmal mitochondria. This uncoupling effect on oxidative phosphorylation was not detectable after short-term exposure to cocaine, suggesting that these mitochondrial abnormalities were a late rather than a primary event in the pathological response to cocaine. MitoQ, a mitochondrial-targeted antioxidant, was shown to completely prevent these mitochondrial abnormalities as well as cardiac dysfunction characterized here by a diastolic dysfunction studied with a conductance catheter to obtain pressure-volume data. Taken together, these results extend previous studies and demonstrate that cocaine-induced cardiac dysfunction may be due to a mitochondrial defect.

Clinical management of cocaine body packers: the Hillingdon experience

BACKGROUND

International smuggling of cocaine by internal concealment is a serious and growing problem. People who engage in this practice are commonly referred to as body packers or mules. The most serious risks associated with body packing include intestinal obstruction and death from cocaine intoxication. These patients were previously managed primarily by surgical retrieval. This was associated with significant mortality due to rupture of poorly constructed cocaine packages. More recently, conservative management using whole bowel irrigation with polyethylene-glycol (Klean-prep Norgine) has been shown to be safe for most patients. To date, however, a consistent approach for the management of these patients has not been established.

METHODS

We retrospectively reviewed the case notes, prescription charts and radiological investigations of all body packers admitted to our unit between 2000 and 2005, concentrating on initial management, complications and outcome.

RESULTS

We identified 61 patients for inclusion. Of these, 56 were managed conservatively with a selection of aperients and laxatives. Six patients were treated successfully for cocaine toxicity and 5 required surgical retrieval of cocaine packets.

CONCLUSION

Our results confirm the safety of a conservative approach. Based on our experience and a review of the literature, we have devised a treatment protocol to reduce the risk of complications and the length of stay in hospital.

Molecular mechanisms of psychostimulant addiction

Drug addiction represents a pathological form of neuroplasticity along with the emergence of aberrant behaviors involving a cascade of neurochemical changes mainly in the brain's rewarding circuitry. The aberrant behavioral phenotypes can be assessed by an animal model of drug-induced behavioral sensitization, which is characterized by an initiation stage that is formed in the ventral tegmental area and a behavioral expression stage determined mainly in the nucleus accumbens. Numerous studies during past decades demonstrate that the mesocorticolimbic dopamine pathway plays an essential role in the development of behavioral sensitization. Moreover, a series of cellular signaling pathways and gene expression determine the severity of addictive behaviors. In addition to the well-characterized dopamine D1 receptor-mediated cAMP/protein kinase A up-regulation in the nucleus accumbens, recent reports indicate the cellular mediator dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) and transcription regulator DeltaFosB are associated with the accumbal PKA pathway to modulate the development of behavioral sensitization. The finding of cAMP-independent and dopamine D2 receptor-mediated Akt/GSK3 in activation in the nucleus accumbens of behaviorally sensitized animals implies that a signal cascade down-stream of both dopamine D1 and D2 receptors comprises the mainstay of the addiction network. This review outlines the cellular pathways that have been demonstrated to participate in psychostimulant addiction, focused particularly in the nucleus accumbens.

Pathways to adult marijuana and cocaine use: a prospective study of African Americans from age 6 to 42

This study examines pathways to adult marijuana and cocaine use in a cohort of African Americans from Woodlawn, an inner city community in Chicago. Assessments were conducted in first grade (age 6), adolescence (age 16), early adulthood (age 32), and in mid-adulthood (age 42). The "social adaptation life course "framework guided the focus on social adaptation, social bonds, and economic resources as predictors of adult drug use. Results indicate that more frequent substance use in adolescence and lower-income and less-frequent church attendance in early adulthood increase the risk of mid-life drug use. Shyness in first grade related inversely to later cocaine use and marijuana use (marginally significant). Indirect pathways to drug use also were identified. Gender differences were not significant. The findings show continuities in social maladaptation over time and the importance of social integration and economic resources in the early adult years.

Effects of serotonin (5-HT)(1B) receptor ligands on cocaine-seeking behavior in rats

Numerous data indicated a significance for the brain dopaminergic pathways in the behavioral effects of cocaine, however recent research also demonstrated involvement of serotonin (5-HT) neurotransmission and particularly 5-HT(1B) receptors in the reinforcing, discriminative stimulus and sensitizing effects of cocaine. In order to substantiate a role of these receptors in incentive motivation for cocaine, we used the extinction/reinstatement model to examine the effects of the 5-HT(1B) receptor ligands on reinstatement of extinguished cocaine-seeking behavior and food-taking behavior. Rats trained to self-administer cocaine (0.5 mg/kg/infusion) subsequently underwent extinction procedures. They were then tested for the cocaine-primed or cocaine-associated cue-induced reinstatement of extinguished cocaine-seeking behavior. Other groups of rats were trained to self-administer food (sweet milk), and after extinction they were tested for the reinstatement of food-taking behavior induced by contingent food presentation. The 5-HT(1B) receptor antagonists SB 216641 (2.5-7.5 mg/kg) and GR 127935 (2.5-10 mg/kg) dose-dependently attenuated the cocaine (10 mg/kg)- and cocaine-associated cue-induced reinstatement of cocaine-seeking behavior whereas they failed to alter reinstatement of food-taking behavior. The 5-HT(1B) receptor agonist CP 94253 (2.5 or 5 mg/kg) combined with a subthreshold priming dose of cocaine (2.5 mg/kg) potentiated reinstatement of the drug seeking-behavior, but inhibited cocaine seeking induced by a submaximal dose (10 mg/kg) of cocaine or the cocaine-associated cue. Moreover, the 5-HT(1B) receptor agonist attenuated reinstatement of food-taking behavior. Facilitatory effect of CP 94253 on cocaine-seeking behavior and its inhibitory effect on food-taking behavior were blocked by SB 216641, but its inhibitory effect on cocaine-seeking behavior remained unaffected by this 5-HT(1B) receptor antagonist. Our results indicate that tonic activation of 5-HT(1B) receptors is involved in cocaine- and cue-induced reinstatement of cocaine-seeking behavior and that the inhibitory effects of 5-HT(1B) receptor antagonists on these phenomena are directly related to motivational aspects of cocaine abuse. The facilitatory 5-HT(1B) receptor-mediated effect of the 5-HT(1B) receptor agonist on cocaine seeking may be related to the earlier reported enhancement of the rewarding properties of cocaine, while its inhibitory effect on cocaine-seeking behavior, unrelated to the 5-HT(1B) receptor activation, may result from a general reduction of motivation.

Quality of Web-based information on cocaine addiction

OBJECTIVE

To evaluate the quality of web-based information on cocaine use and addiction and to investigate potential content quality indicators.

METHODS

Three keywords: cocaine, cocaine addiction and cocaine dependence were entered into two popular World Wide Web search engines. Websites were assessed with a standardized proforma designed to rate sites on the basis of accountability, presentation, interactivity, readability and content quality. "Health on the Net" (HON) quality label, and DISCERN scale scores aiding people without content expertise to assess quality of written health publication were used to verify their efficiency as quality indicators.

RESULTS

Of the 120 websites identified, 61 were included. Most were commercial sites. The results of the study indicate low scores on each of the measures including content quality. A global score (the sum of accountability, interactivity, content quality and aesthetic criteria) appeared as a good content quality indicator.

CONCLUSIONS

While cocaine education websites for patients are widespread, their global quality is poor. There is a need for better evidence-based information about cocaine use and addiction on the web.

PRACTICE IMPLICATIONS

The poor and variable quality of web-based information and its possible impact on physician-patient relationship argue for a serious provider for patient talk about the health information found on Internet. Internet sites could improve their content using the global score as a quality indicator.

Cocaine seeking habits depend upon dopamine-dependent serial connectivity linking the ventral with the dorsal striatum

A neuroanatomical principle of striatal organization has been established through which ventral domains, including the nucleus accumbens, exert control over dorsal striatal processes mediated by so-called "spiraling," striato-nigro-striatal, circuitry. We have investigated the functional significance of this circuitry in the control over a cocaine-seeking habit by using an intrastriatal disconnection procedure that combined a selective, unilateral lesion of the nucleus accumbens core and infusion of a dopamine receptor antagonist into the contralateral dorsolateral striatum, thereby disrupting striato-midbrain-striatal serial connectivity bilaterally. We show that this disconnection selectively decreased drug-seeking behavior in rats extensively trained under a second-order schedule of cocaine reinforcement. These data thereby define the importance of interactions between ventral and dorsal domains of the striatum, mediated by dopaminergic transmission, in the neural mechanisms underlying the development and performance of cocaine-seeking habits that are a key characteristic of drug addiction.

DeltaFosB induction in orbitofrontal cortex mediates tolerance to cocaine-induced cognitive dysfunction

Current cocaine users show little evidence of cognitive impairment and may perform better when using cocaine, yet withdrawal from prolonged cocaine use unmasks dramatic cognitive deficits. It has been suggested that such impairments arise in part through drug-induced dysfunction within the orbitofrontal cortex (OFC), yet the neurobiological mechanisms remain unknown. We observed that chronic cocaine self-administration increased expression of the transcription factor deltaFosB within both medial and orbitofrontal regions of the rat prefrontal cortex. However, the increase in OFC deltaFosB levels was more pronounced after self-administered rather than experimenter-administered cocaine, a pattern that was not observed in other regions. We then used rodent tests of attention and decision making to determine whether deltaFosB within the OFC contributes to drug-induced alterations in cognition. Chronic cocaine treatment produced tolerance to the cognitive impairments caused by acute cocaine. Overexpression of a dominant-negative antagonist of deltaFosB, deltaJunD, in the OFC prevented this behavioral adaptation, whereas locally overexpressing deltaFosB mimicked the effects of chronic cocaine. Gene microarray analyses identified potential molecular mechanisms underlying this behavioral change, including an increase in transcription of metabotropic glutamate receptor subunit 5 and GABA(A) receptors as well as substance P. Identification of deltaFosB in the OFC as a mediator of tolerance to the effects of cocaine on cognition provides fundamentally new insight into the transcriptional modifications associated with addiction.

Kappa agonist-induced reinstatement of cocaine seeking in squirrel monkeys: a role for opioid and stress-related mechanisms

Kappa opioid agonists were at one time proposed as candidate pharmacotherapies for cocaine addiction, mainly because of their ability to decrease dopamine neurotransmission and attenuate the behavioral effects of cocaine in laboratory animals. Recent studies, however, suggest that kappa agonists also may mimic and/or enhance some of the effects of cocaine through mechanisms related to stress. The current study used a reinstatement procedure to examine the ability of the kappa agonists spiradoline and enadoline to reinstate extinguished cocaine seeking in squirrel monkeys previously trained to self-administer cocaine under a second-order schedule of i.v. drug injection. Opioid- and stress-related mechanisms were evaluated in antagonism studies with the opioid antagonists naltrexone and nor-binaltorphimine (nor-BNI), the corticotropin-releasing factor receptor antagonist butyl-ethyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo [2,3-d]pyrimidin-4-yl]amine (CP 154,526), and the alpha(2)-adrenoceptor agonist clonidine combined with either spiradoline or enadoline. When tested alone, priming with spiradoline and enadoline induced significant reinstatement of cocaine-seeking behavior to approximately 45% of the maximum reinstatement induced by cocaine. Reinstatement of cocaine seeking induced by intermediate doses of spiradoline was greater in the presence than in the absence of response-contingent presentations of a cocaine-paired stimulus. Spiradoline- and enadoline-induced reinstatement of drug seeking was attenuated by naltrexone but not by nor-BNI. Spiradoline-induced reinstatement of cocaine seeking was also antagonized by CP 154,526 and clonidine. The results point to interactions between a subpopulation of kappa opioid receptors and central corticotropin-releasing factor and noradrenergic stress systems in the reinstatement of cocaine seeking induced by kappa agonists.

Protracted 'pro-addictive' phenotype produced in mice by pre-adolescent phenylpropanolamine

For decades, the sympathomimetic phenylpropanolamine (PPA; +/- -norepinephrine) was an active ingredient found in popular children's over-the-counter (OTC) cold, cough, and allergy medications. To examine the possibility that pre-adolescent PPA exposure may induce neuroadaptations that influence behavioral and neurochemical responding to cocaine, C57BL/6J mice were pretreated with PPA (0-40 mg/kg) during postnatal days 21-31. The behavioral and neurochemical responses to acute and repeated cocaine (4 x 15 mg/kg) were then assessed in adulthood when the mice were 10 weeks of age. Whereas pre-adolescent PPA exposure did not influence the acute locomotor response to 15 mg/kg cocaine, PPA pre-exposure dose-dependently enhanced the expression of cocaine-induced place conditioning, reduced the expression of locomotor sensitization, but did not influence cocaine-induced stereotypy. Pre-adolescent PPA exposure completely prevented the capacity of cocaine to elevate extracellular levels of catecholamines in the nucleus accumbens, but facilitated the development of cocaine-induced glutamate sensitization. Neither acute nor repeated cocaine altered extracellular GABA levels in the accumbens of control mice; however, 15 mg/kg cocaine lowered GABA levels by approximately 40% in PPA pretreated mice and this effect showed tolerance with repeated cocaine administration. These data provide the first evidence that early exposure to an OTC compound produces protracted effects upon cocaine-induced changes in nucleus accumbens neurotransmission that may contribute to a 'pro-addictive' phenotype in adulthood.

Stress-induced relapse to cocaine seeking: roles for the CRF(2) receptor and CRF-binding protein in the ventral tegmental area of the rat

RATIONALE

Footshock reinstates cocaine seeking in cocaine-experienced rats by inducing corticotropin-releasing factor (CRF) and glutamate release in the ventral tegmental area (VTA) and thus activating VTA dopaminergic neurons. Footshock-induced VTA glutamate release, dopamine activation and reinstatements are blocked by VTA administration of a alpha-helical CRF, a nonselective CRF receptor antagonist. The effects of selective CRF antagonists have not yet been reported.

OBJECTIVE

The present studies were designed to explore the roles of VTA CRF receptor subtypes and CRF-BP in these effects induced by footshock.

METHODS

Rats were first trained to lever-press for intravenous cocaine (1 mg/infusion/0.13 ml, FR-1 schedule), and then tested under extinction conditions until response rates returned to the pretraining baseline. Reinstatements, VTA glutamate and dopamine levels [microdialysis with high performance liquid chromatography (HPLC)] were then assessed, under various pharmacological conditions, after mild inescapable footshock.

RESULTS

Footshock-induced reinstatement of cocaine seeking and release of VTA glutamate and dopamine were blocked by selective blockade of VTA CRF(2) receptors (CRF(2)Rs) but not CRF(1)Rs. VTA perfusion of CRF or CRF(2)R agonists that have strong affinity for CRF-BP mimicked the effects induced by footshock while CRFR agonists that do not bind CRF-BP were ineffective. CRF(6-33), which competes for the CRF binding site on CRF-BP, attenuated the effects of CRF or urocortin I on VTA glutamate and dopamine release and on reinstatement of cocaine seeking.

CONCLUSIONS

The present studies revealed a role of VTA CRF-BP and suggest an involvement of CRF(2)R in the effectiveness of stress in triggering glutamate and dopamine release and cocaine seeking in drug-experienced animals.

Interactions among ovarian hormones and time of testing on behavioral sensitization and cocaine self-administration

Ovarian hormones play a role in the use of drugs of abuse in women. In female rats estradiol has been shown to enhance acquisition of cocaine self-administration and behavioral sensitization induced by repeated cocaine treatment. Experiments were conducted to determine the effects of estradiol and/or progesterone on cocaine self-administration and behavioral sensitization to cocaine (10mg/kg; in animals with unilateral 6-hydroxydopamine lesions). Five groups of ovariectomized females were tested: (1) oil vehicle; (2) estradiol (E); (3) progesterone (P); (4) estradiol and progesterone given concurrently (EPC); (5) estradiol and progesterone given sequentially (EPS: 3 days of estradiol, 1 day progesterone, 1 day oil). All animals were tested during the dark phase of the light:dark cycle at ZT1600 and ZT2000-2100. Behavioral sensitization results: there was substantial conditioned turning throughout the habituation periods, and all animals exhibited behavioral sensitization with repeated cocaine treatment. Multivariate analysis indicated a significant effect of hormone treatment, time of day and day of testing. When individual groups were compared, however, only at ZT1600 did the E-treated and the EPS-treated animals show a trend (p<0.06) for greater behavioral sensitization to cocaine relative to the oil-treated animals. Self-administration results: all groups showed rapid acquisition of cocaine self-administration at 0.3 mg/kg/infusion, so we did not see an effect of ovarian hormones on acquisition, or a difference between groups tested at ZT1600 versus ZT2100 (p<0.05). There was, however, enhanced total intake of cocaine at 0.75 mg/kg/infusion in the E and the EPS groups. Concurrent administration of progesterone with estradiol counteracted the effect of estradiol on cocaine intake at 0.75 mg/kg/infusion, while progesterone alone did not enhance cocaine self-administration.

Cocaine-induced decision-making deficits are mediated by miscoding in basolateral amygdala

Addicts and drug-experienced animals have decision-making deficits in reversal-learning tasks and more complex 'gambling' variants. Here we show evidence that these deficits are mediated by persistent encoding of outdated associative information in the basolateral amygdala. Cue-selective neurons in the basolateral amygdala, recorded in cocaine-treated rats, failed to change cue preference during reversal learning. Further, the presence of these neurons was critical to the expression of the reversal-learning deficit in the cocaine-treated rats.

Extended access to cocaine self-administration enhances drug-primed reinstatement but not behavioral sensitization

Cocaine addicts increase the frequency and amount of drug use over time. This characteristic has been modeled by escalating drug intake in rats that were given extended access to cocaine. However, it remains unclear whether the behavior of escalating drug intake or simply increased drug dose is the relevant aspect of this model. The present study investigated whether the phenomenon of escalated drug-taking enhances cocaine-induced sensitization and reinstatement. Rats were trained to self-administer cocaine during daily 1-h sessions for 7 days. A short-access (ShA) group continued to receive 1-h sessions for 10 days while a group of rats was switched to 6 h of drug access, long-access (ShA-LgA) group, for 10 days. In addition, a long-access only (LgA-only) group was added that was not pretrained but was only given extended access for 10 days. ShA subjects maintained stable drug intake; ShA-LgA subjects escalated intake while LgA-only subjects decreased drug intake. All groups displayed an inverted-U shaped cocaine dose-response curve in both the sensitization and reinstatement tests. There was no difference in the expression of behavioral sensitization between groups. Whereas both long-access groups showed reinstatement at more doses of cocaine than the ShA group, the presence of escalation did not affect reinstatement. These results indicate that extended access to cocaine self-administration produces behavioral differences relative to traditional short-access animals in reinstatement, but not sensitization. Furthermore, the differences in reinstatement are predicted more by length of cocaine access than by escalation of drug intake.

Noradrenergic mechanisms in cocaine-induced reinstatement of drug seeking in squirrel monkeys

Norepinephrine (NE) uptake and NE receptor mechanisms play important modulating roles in the discriminative stimulus and stimulant effects of cocaine. The present study investigated the role of NE mechanisms in cocaine priming-induced reinstatement of extinguished drug seeking. Squirrel monkeys (Saimiri sciureus) were trained to stability under a second-order fixed interval, fixed ratio schedule of drug self-administration in which operant responding was maintained jointly by i.v. cocaine injections and presentations of a cocaine-paired stimulus. Drug seeking was then extinguished by replacing cocaine with vehicle and eliminating the cocaine-paired stimulus. In test sessions during which the cocaine-paired stimulus was reintroduced but only vehicle was available for self-administration, priming with cocaine, the dopamine transport inhibitor 1-[2-[bis-(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine (GBR 12909), and the NE transport inhibitors nisoxetine and talsupram induced dose-dependent reinstatement of drug seeking. The maximum effect of the NE transport inhibitors was less than half that of cocaine. Both nisoxetine and talsupram augmented the priming effects of a low but not a high dose of cocaine. The priming effects of nisoxetine were blocked by the alpha1-adrenoceptor antagonist prazosin, the alpha2-adrenoceptor agonist clonidine, and the beta-adrenoceptor antagonist propranolol, but not by the dopamine receptor antagonist flupenthixol. The priming effects of cocaine were antagonized by clonidine and flupenthixol. Neither nisoxetine nor cocaine increased physiological (salivary cortisol) or behavioral (self-directed behaviors) markers of stress. These findings suggest that NE transporter inhibition and alpha2-adrenoceptor mechanisms play a significant role in cocaine-induced reinstatement of drug seeking that is not secondary to activation of brain stress pathways.

A qualitative and quantitative review of cocaine-induced craving: the phenomenon of priming

Drug-induced craving is thought to play an important role in relapse occasioned by a "slip", or an isolated use of a previously abused drug after a period of abstinence. Clinical experience suggests that acute exposure to cocaine elicits craving (hereafter referred to as "priming"); however, this has received surprisingly little attention in the clinical literature.

AIMS

The intentions of this review are to provide a qualitative review of the literature as well as a more stringent quantitative review of the existence and presence of cocaine-induced priming effects.

METHODS

In order to determine whether priming effects occur following cocaine administration, we conducted qualitative and quantitative reviews of studies in which participants received cocaine under experimentally controlled conditions in the laboratory.

RESULTS

The results of the qualitative review were equivocal, while the quantitative review revealed that cocaine administration was associated with a significant increase in craving for cocaine, and the effect size of this relationship was large.

CONCLUSION

A review of the individual studies revealed marked variability, suggesting that priming effects did not occur consistently and that there may be factors that mediate or moderate the intensity of the priming effects induced by cocaine. The implications of these findings are discussed.

Withdrawal from a single exposure to cocaine increases 5-HT2A receptor and G protein function

We previously reported that withdrawal from chronic cocaine produces supersensitivity of serotonin 2A receptors. We report here the minimum cocaine exposure necessary to produce withdrawal-associated increases in serotonin 2A receptor signaling in the frontal cortex. Rats withdrawn from cocaine treatments of 1, 3 or 7 days exhibited increases in G protein-stimulated and serotonin 2A receptor-stimulated phospholipase C activity in the frontal cortex. A single cocaine injection produced withdrawal-induced changes comparable to that produced by repeated exposure. None of these cocaine treatment paradigms are associated with changes in the levels of serotonin 2A receptors, Galphaq or Galpha11 proteins. These data demonstrate that only a single exposure to cocaine can produce unique withdrawal-associated neuroadaptations in serotonin 2A receptor signaling in the frontal cortex, which may be clinically relevant with respect to drug relapse.

A case of late-onset dependence on cocaine and crack

AIMS

To raise awareness among the professional clinical and research community of the risk of cocaine misuse among elderly patients.

METHODS

Case report of a male patient, aged 72 years, who presented to a community substance misuse service with cocaine use disorder (hydrochloride and base form).

RESULTS

The development of the disorder was marked by high levels of cocaine (and later crack cocaine use), repeated periods of abstinence followed by relapse in the past 4 years, with severe consequences to the patient and his family. Treatment involved a close collaboration between several specialist addictions and old-age psychiatry teams in National Health Service.

IMPLICATIONS

Although dependence on cocaine among the elderly is considered very rare, clinical management can be challenging and is likely to require the involvement of several specialist and general health services.

A cocaine-associated quadriplegia and motor aphasia after first use of cocaine

A 31-year-old female who have snorted one "line" of cocaine hydrochloride (approximately 35 mg), for the first time in her life, was admitted to the hospital because of acute onset of right hemiplegia and left hemiparesis evolving into quadriplegia. Motor aphasia, right eye-ball divergent strabismus and right mouth recess lowering were also observed.

CONCLUSIONS

A first time mucosal administration of cocaine hydrochloride even in low dose can cause severe neurological complications like quadriplegia and aphasia. Cocaine-associated stroke can be a diagnostic problem in the emergency room. Unconscious patients or those with acute onset of neurological disorders can form a real diagnostic challenge, especially when there is no evidence of previous drug taking.

Affective Modulation of Pain in Substance-Dependent Veterans

OBJECTIVE

Prior work suggests that positive affect inhibits pain while negative affect facilitates it. The current study sought to determine whether: 1) affective modulation of pain extends to a patient population; 2) cocaine and alcohol dependence influences the pattern of modulation; and 3) affective modulation of pain is mediated by changes in arm temperature.

DESIGN

Thirty-seven participants with and without substance dependence (14 alcohol, 13 cocaine, 10 none) attended three experimental sessions intended to induce emotions (negative, neutral, positive) by picture-viewing. Following emotion-induction, participants were asked to submerge their arm in 33 degrees F water and keep it there until they reached tolerance. During submersion, pain ratings were made on a mechanical visual analog scale (M-VAS).

OUTCOME MEASURES

Latency from submersion to first movement of the M-VAS (pain threshold) and latency to arm removal (pain tolerance) were measured. Arm temperature and manipulation checks for emotion-induction (corrugator electromyogram, heart rate, skin conductance, self-report) were also recorded.

RESULTS

Manipulation checks confirmed that targeted affective states were achieved. Pain threshold and tolerance were higher after viewing pleasant pictures than after unpleasant ones. Although arm temperature did vary based on the affect induced, analyses suggested that temperature did not influence pain outcomes.

CONCLUSIONS

Affect modulates pain perception in patients and does not appear to be mediated by changes in arm temperature. Additionally, pain modulation was not significantly influenced by cocaine or alcohol dependence. These data are encouraging, because they suggest that nonpharmacological methods of pain modulation may be effective in substance-dependent individuals.

Involvement of cannabinoid CB1 receptors in drug addiction: effects of rimonabant on behavioral responses induced by cocaine

A lot of evidence indicate that endocannabinoids and cannabinoid CB(1) receptors are implicated in drug addiction. In the present study, we investigated the effect of the cannabinoid CB(1) receptor antagonist/partial agonist rimonabant on the cocaine-maintained reinforcement and relapse to cocaine seeking as well as on the cocaine challenge-induced hyperactivity in sensitized rats and on discriminative stimulus effects of cocaine in rats. We found that endocannabinoids were not involved in maintenance of cocaine reinforcement and its subjective effects since pharmacological blockade of cannabinoid CB(1) receptors altered neither self-administration nor discriminative stimulus effects of cocaine. On the other hand, withdrawal from repeated access or exposure to cocaine and then a reinstatement of cocaine-seeking behavior or a sensitized locomotor response to a single cocaine challenge, respectively, was potently reduced by pretreatment with rimonabant. The latter observations may show that repeated cocaine treatment and the drug withdrawal produce--apart from behavioral effects--also different neural consequences in the endocannabinoid systems in rats.

Cannabinoid CB1 receptor antagonist AM251 inhibits cocaine-primed relapse in rats: role of glutamate in the nucleus accumbens

Blockade of cannabinoid CB1 receptors has been reported to inhibit cocaine- or cocaine cue-induced reinstatement of drug seeking. However, the mechanisms underlying this action are poorly understood. Given the importance of dopamine, glutamate, and GABA in cocaine reward and relapse, we studied the effects of AM251 [N-(piperidin-1-yl)-5-(4-iodophonyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide], a novel highly selective CB1 receptor antagonist, on cocaine-primed reinstatement of drug-seeking behavior and on cocaine-induced changes in extracellular DA, glutamate, and GABA in the nucleus accumbens (NAc) under reinstatement conditions. We found that systemic administration of AM251 selectively inhibited cocaine-induced, but not sucrose plus sucrose cue-induced, reinstatement of reward-seeking behavior. AM251 alone did not trigger reinstatement. Local perfusion of AM251 into the NAc or the dorsal striatum also inhibited cocaine-triggered reinstatement. AM251 alone dose dependently elevated NAc glutamate in a voltage-dependent Na+ channel-dependent manner. AM251 did not affect NAc DA or GABA. Pretreatment with AM251 dose dependently inhibited cocaine-induced increases in NAc glutamate but not in DA. Blockade of NAc metabotropic glutamate mGluR2/3 receptors by LY341495 [(2S)-2-amino-2-[(1S,2S)-2-carboxycycloprop-1-yl]-3-(xanth-9-yl) propanoic acid] slightly facilitated cocaine-enhanced glutamate release but blocked the antagonism of cocaine-induced reinstatement by AM251. These data suggest the following: (1) CB1 receptors exert tonic inhibition over NAc glutamate release under cocaine-extinction conditions; (2) blockade of CB1 receptors by AM251 inhibits cocaine-enhanced NAc glutamate release and cocaine-triggered reinstatement; and (3) these effects appear to be mediated by activation of presynaptic mGluR2/3 autoreceptors secondary to AM251-induced increase (disinhibition) of NAc glutamate release.

An antisense oligodeoxynucleotide to the mu opioid receptor attenuates cocaine-induced behavioral sensitization and reward in mice

Numerous studies support a role for the endogenous opioid system in cocaine-influenced behavior. Few of these studies, however, selectively delineate a role for the mu opioid receptor (MOR) in this regard. This investigation examined if the MOR modulates cocaine-induced behavior in mice using a 17-base antisense oligodeoxynucleotide (AS ODN) directed against the MOR coding sequence 16-32. Specifically, cocaine-induced behavioral sensitization and conditioned reward were investigated. For the sensitization study, C57BL/6J mice received eight intermittent i.c.v. infusions of saline, mismatch oligodeoxynucleotide (ODN) (20 microg/4 microl) or AS ODN (20 microg/4 microl) over 20 days. Mice also received concomitant once daily i.p. injections of saline (4 ml/kg) or cocaine (15 mg/kg) for 10 days. There was a 7-day withdrawal period, after which all mice were challenged with cocaine (15 mg/kg) to test for behavioral sensitization. For the conditioned place preference (CPP) study, mice received five i.c.v. infusions of mismatch ODN or MOR AS ODN (days 1-5). An unbiased counterbalanced conditioning procedure was used where mice were conditioned with saline (4 ml/kg, i.p.) and cocaine (15 mg/kg, i.p.) on alternate days for four sessions (days 3-6). Mice were tested on day 7 for CPP. Immediately following testing, [3H]DAMGO (D-Ala2, N-Me-Phe4, Gly-ol5-enkephalin) receptor binding to brain homogenates was conducted. MOR AS attenuated cocaine-induced behavioral sensitization and conditioned reward. MOR AS ODN also reduced [3H]DAMGO binding. Collectively, these findings implicate the MOR as playing an important neuromodulatory role in the behavioral effects of cocaine in mice.

Anatomy and pharmacology of cocaine priming-induced reinstatement of drug seeking

Cocaine addiction in human addicts is characterized by a high rate of relapse following successful detoxification. Relapse to drug taking/seeking can be precipitated by several stimuli including, but not limited to, re-exposure to cocaine itself. In order to understand the mechanisms underlying cocaine craving, a substantial effort has been devoted to elucidating the anatomical and neurochemical bases underlying cocaine priming-induced reinstatement, an animal model of relapse. Here, we review evidence that changes in dopaminergic and glutamatergic transmission in limbic/basal ganglia circuits of interconnected nuclei including the medial prefrontal cortex, nucleus accumbens, ventral pallidum, amygdala, hippocampus, orbitofrontal cortex, neostriatum and thalamus underlie cocaine priming-induced reinstatement of cocaine seeking. Maladaptive changes in the processing of motivationally relevant stimuli by these circuits following cocaine self-administration result in drug craving and compulsive drug seeking upon re-exposure to cocaine.

Topographic imaging of quantitative EEG in response to smoked cocaine self-administration in humans

Quantitative electroencephalographic (qEEG) profiles were studied in cocaine-dependent patients in response to an acute, single-blind, self-administered dose of smoked cocaine base (50 mg) vs placebo. qEEG data were averaged using neurometric analytical methods and the spectral power of each primary bandwidth was computed and topographically imaged. Additional measures included cocaine-induced high, craving, and related subjective ratings, heart rate, blood pressure, and plasma cortisol and homovanillic acid levels. In all, 13 crack cocaine-dependent subjects were tested. Cocaine produced a rapid increase in subjective ratings of cocaine high and good drug effect, and a more persistent increase in cocaine craving and nervousness. Cocaine also produced a rapid rise in heart rate and a prolonged increase in plasma cortisol. Placebo, administered in the context of cocaine cues and dosing expectations, had no cocaine-like subjective or physiological effects. Cocaine produced a rapid increase in absolute theta, alpha, and beta power over the prefrontal cortex (FP1, FP2), lasting up to 25 min after dosing. The increase in theta power was correlated with good drug effect, and the increase in alpha power was correlated with nervousness. Cocaine also produced a similar increase in delta coherence over the prefrontal cortex, which was positively correlated with plasma cortisol, and negatively correlated with nervousness. Placebo resulted in an increase in alpha power over the prefrontal cortex. These data demonstrate the involvement of prefrontal cortex in the qEEG response to acute cocaine. Evidence indicates slow wave qEEG, delta and theta activity, involvement in the rewarding properties of cocaine.

Cocaine experience establishes control of midbrain glutamate and dopamine by corticotropin-releasing factor: a role in stress-induced relapse to drug seeking

Footshock stress can reinstate cocaine-seeking behavior through a central action of the stress-associated neurohormone corticotropin-releasing factor (CRF). Here we report (1) that footshock stress releases CRF in the ventral tegmental area (VTA) of the rat brain, (2) that, in cocaine-experienced but not in cocaine-naive rats, this CRF acquires control over local glutamate release, (3) that CRF-induced glutamate release activates the mesocorticolimbic dopamine system, and (4) that, through this circuitry, footshock stress triggers relapse to drug seeking in cocaine-experienced animals. Thus, a long-lasting cocaine-induced neuroadaptation, presumably at the level of glutamate terminals in the VTA, appears to play an important role in stress-induced relapse to drug use. Similar neuroadaptations may be important for the comorbidity between addiction and other stress-related psychiatric disorders.

Alterations in BDNF and trkB mRNAs following acute or sensitizing cocaine treatments and withdrawal

In the present study, we used in situ hybridization to examine the influence of acute or repeated cocaine administrations and withdrawal from repeated cocaine treatment on the level of brain-derived neurotrophic factor (BDNF) and its receptor trkB mRNAs in rat brain. Cocaine (10 mg/kg i.p.) injected acutely produced locomotor hyperactivation, while repeated (single injection for 5 days) administrations of cocaine (10 mg/kg) induced a two-fold increases in the locomotor activity in rats in response to a challenge cocaine dose (10 mg/kg) on day 10, as compared to the saline-treated animals (sensitization). Cocaine treatments induced a brain-region-specific decrease in the levels of trkB mRNA. On the other hand, BDNF mRNA in the rat hippocampus was increased only in the group of rats subjected to cocaine withdrawal. Animals under cocaine withdrawal demonstrated a significant increase in the immobility time measured by the use of modified forced swimming test. Therefore, the increases in the levels of BDNF mRNA in the rat hippocampus seem to be correlated with "depressive-like" behavioral effects during withdrawal from repeated cocaine treatment. In the shell (but not in the core) of the nucleus accumbens, the levels of BDNF mRNA were significantly increased following acute and repeated cocaine treatment as well as during cocaine withdrawal, which indicates that the alterations in the neurotrophin level in the brain region important for the expression of cocaine-induced sensitization involve other mechanisms.

Cocaine dependence and PTSD: a pilot study of symptom interplay and treatment preferences

Cocaine dependence and posttraumatic stress disorder (PTSD) frequently co-occur. Little is known, however, about patients' perceptions of symptom connectedness and preferences for treatment. This pilot study preliminarily investigated perceptions of symptom interplay and preferences regarding concurrent or sequential models of psychotherapy, therapy format, and treatment modalities. Participants were 23 individuals with current cocaine dependence and PTSD. The majority (95.5%) reported a functional relationship between cocaine use and PTSD symptoms (p<0.001). Improvement in PTSD symptoms was typically (63.6%) associated with a decrease in cocaine use (p<0.01). Similarly, a worsening of PTSD symptoms was typically (86.4%) associated with an increase in cocaine use (p<0.001). In contrast, improvement/deterioration in cocaine use was not significantly related to subsequent improvement/deterioration in PTSD symptoms. This finding suggests that changes in PTSD may be an important risk factor to consider among individuals with cocaine dependence and PTSD. Approximately 41% preferred a concurrent model of therapy in which the cocaine use and PTSD are treated simultaneously in therapy. The findings highlight the functional relationship between these two disorders and have direct implications for treatment interventions.

Activation of central neurokinin-1 receptors induces reinstatement of cocaine-seeking behavior

A number of neurochemical systems have been implicated in mediating relapse to drug-seeking behavior. Substance P (SP) is a neuropeptide that interacts with some of these systems, suggesting a possible role for SP and its preferred receptor, the neurokinin-1 (NK-1) receptor, in the mediation of relapse. In this study, we examined whether selective activation of NK-1 receptors induces reinstatement of cocaine-seeking behavior, and whether endogenous activity at these receptors is involved in mediating cocaine-induced reinstatement. For each experiment, rats were trained to self-administer cocaine for 8--10 days, and following a period of extinction, tests for reinstatement were given. To examine the effects of NK-1 receptor activation on reinstatement of cocaine-seeking behavior, animals received an intracerebroventricular (ICV) infusion of the selective NK-1 receptor agonist, [Sar(9)Met(O(2))(11)]-SP (0, 1, 3 microg), immediately prior to the test session. To examine the role of endogenous NK-1 receptor activity on cocaine-induced reinstatement, rats were pretreated with ICV infusions of the selective NK-1 receptor antagonists, RP 67580 (0, 0.1, 0.5, 2.5 nmol) or GR 82334 (0, 2, 10, 50 pmol), prior to systemic priming injections of cocaine (10mg/kg or 20mg/kg; i.p.). The results showed that [Sar(9)Met(O(2))(11)]-SP induced reinstatement of cocaine-seeking behavior, but that RP 67580 and GR 82334 had no effect on cocaine-induced reinstatement. These findings suggest that while activation of NK-1 receptors is capable of inducing reinstatement of cocaine-seeking behavior, endogenous activity at these receptors is not involved in mediating the priming effects of cocaine on reinstatement of drug-seeking behavior.