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RATIONALE: Cannabidiol (CBD) reduces craving in animal models of alcohol and cocaine use and is known to modulate nicotinic receptor function, suggesting that it may alleviate symptoms of nicotine withdrawal. However, preclinical evaluation of its efficacy is still lacking. OBJECTIVES: The goal of this study was to test the preclinical efficacy of a chronic CBD treatment in reducing nicotine dependence using measures of withdrawal symptoms including somatic signs, hyperalgesia, and weight gain during acute and protracted abstinence. METHODS: Male and female Wistar rats were made dependent on nicotine using osmotic minipumps (3.15 mg/kg/day) for two weeks, after which minipumps were removed to induce spontaneous withdrawal. Three groups received CBD injections at doses of 7.5, 15, and 30 mg/kg/day for two weeks, starting one week into chronic nicotine infusion. The control groups included rats with nicotine minipumps that received vehicle injections of sesame oil instead of CBD; rats implanted with saline minipumps that received sesame oil injections (double vehicle) or the highest dose of CBD 30mg/kg/day. Throughout the experiment, serum was collected for determination of CBD and nicotine concentrations, mechanical sensitivity threshold and withdrawal scores were measured, and body weight was recorded. RESULTS: CBD prevented rats from exhibiting somatic signs of withdrawal and hyperalgesia during acute and protracted abstinence. There was no dose-response observed for CBD, suggesting a ceiling effect at the doses used and the potential for lower effective doses of CBD. The saline minipump group did not show either somatic signs of withdrawal or hyperalgesia during acute and protracted abstinence, and the highest dose of CBD used (30mg/kg/day) did not alter these results. CONCLUSIONS: This preclinical study suggests that using CBD as a strategy to alleviate the withdrawal symptoms upon nicotine-cessation may be beneficial.

The debate about electronic cigarettes is dividing healthcare professionals, policymakers, manufacturers, and communities. A key limitation in our understanding of the cause and consequences of vaping is the lack of animal models of nicotine vapor self-administration. Here, we developed a novel model of voluntary electronic cigarette use in rats using operant behavior. We found that rats voluntarily exposed themselves to nicotine vapor to the point of reaching blood nicotine levels that are similar to humans. The level of responding on the active (nicotine) lever was similar to the inactive (air) lever and lower than the active lever that was associated with vehicle (polypropylene glycol/glycerol) vapor, suggesting low positive reinforcing effects and low nicotine vapor discrimination. Lever pressing behavior with nicotine vapor was pharmacologically prevented by the α4β2 nicotinic acetylcholine receptor partial agonist and α7 receptor full agonist varenicline in rats that self-administered nicotine but not vehicle vapor. Moreover, 3 weeks of daily (1 h) nicotine vapor self-administration produced addiction-like behaviors, including somatic signs of withdrawal, allodynia, anxiety-like behavior, and relapse-like behavior after 3 weeks of abstinence. Finally, 3 weeks of daily (1 h) nicotine vapor self-administration produced cardiopulmonary abnormalities and changes in α4, α3, and β2 nicotinic acetylcholine receptor subunit mRNA levels in the nucleus accumbens and medial prefrontal cortex. These findings validate a novel animal model of nicotine vapor self-administration in rodents with relevance to electronic cigarette use in humans and highlight the potential addictive properties and harmful effects of chronic nicotine vapor self-administration.

RATIONALE: Over the last decade, oxycodone has become one of the most widely abused drugs in the USA. Oxycodone use disorder (OUD) is a serious health problem that has prompted a need to develop animal models of OUD that have both face and predictive validity. Oxycodone use in humans is more prevalent in women and leads to pronounced hyperalgesia and irritability during withdrawal. However, unclear is whether current animal models of oxycodone self-administration recapitulate these characteristics in humans. OBJECTIVES: We assessed the face validity of a model of extended-access oxycodone self-administration in rats by examining the escalation of oxycodone intake and behavioral symptoms of withdrawal, including irritability-like behavior and mechanical nociception, in male and female Wistar rats. RESULTS: Both male and female rats escalated their oxycodone intake over fourteen 12-h self-administration sessions. After escalation, female rats administered more drug than male rats. No differences in plasma oxycodone levels were identified, but males had a significantly higher level of oxycodone in the brain at 30 min. Extended access to oxycodone significantly decreased aggressive-like behavior and increased defensive-like behaviors when tested immediately after a 12-h self-administration session, followed by a rebound increase in aggressive-like behavior 12 h into withdrawal. Tests of mechanical nociception thresholds during withdrawal indicated pronounced hyperalgesia. No sex differences in irritability-like behavior or pain sensitivity were observed. CONCLUSIONS: The present study demonstrated the face validity of the extended access model of oxycodone self-administration by identifying sex differences in the escalation of oxycodone intake and pronounced changes in pain and affective states.

The orexin (Orx) system is known to play a critical role in drug addiction and reward-related behaviors. The dynorphin (Dyn) system, conversely, promotes depressive-like behavior and plays a key role in the aversive effects of stress. Orexin and Dyn are co-released and have opposing functions in reward and motivation in the ventral tegmental area (VTA). Earlier studies showed that microinjections of OrxA in the posterior paraventricular nucleus of the thalamus (pPVT) exerted priming-like effects and reinstated cocaine-seeking behavior, suggesting that Orx transmission in the pPVT participates in cocaine-seeking behavior. The present study sought to determine whether Orx and Dyn interact in the pPVT. Using a cellular approach, brain slices were prepared for whole-cell recordings and to study excitatory transmission in pPVT neurons. The superfusion of OrxA increased spontaneous glutamatergic transmission by increasing glutamate release onto pPVT neurons, whereas DynA decreased glutamate release. Furthermore, the augmentation of OrxA-induced glutamate release was reversed by DynA. To corroborate the electrophysiological data, separate groups of male Wistar rats were trained to self-administer cocaine or sweetened condensed milk (SCM). After self-administration training, the rats underwent extinction training and were tested with intra-pPVT administration of OrxA±DynA under extinction conditions. OrxA reinstated cocaine-and SCM-seeking behavior, with a greater effect in cocaine animals. DynA selectively blocked OrxA-induced cocaine seekingvs. SCM seeking. The data indicate that DynA in the pPVT prevents OrxA-induced cocaine seeking, perhaps by reversing the OrxA-induced increase in glutamate release, identifying a novel therapeutic target to prevent cocaine relapse.

Buprenorphine's clinical use is approved for the treatment of heroin addiction; however, evidence supporting its efficacy in cocaine abuse also exists. While for heroin it has been demonstrated that the effect of buprenorphine is mediated by its ability to activate μ-opioid peptide receptor (MOP) receptors, the mechanism through which it attenuates cocaine intake remains elusive. We explored this mechanism using operant models where rodents were trained to chronically self-administer cocaine for 2 hours daily. Buprenorphine (0.3, 1.0 and 3.0 mg/kg) given intraperitoneally 90 minutes before access to cocaine significantly and dose dependently reduced its intake. Pre-treatment with naltrexone or with the selective nociceptin/orphanin FQ peptide (NOP) antagonist SB-612111 did not prevent buprenorphine-induced reduction of cocaine intake. However, when naltrexone and SB-612111 were combined, the effect of buprenorphine on cocaine was completely prevented. To confirm that co-activation of MOP and NOP receptors is the underlying mechanism through which buprenorphine reduces cocaine intake, three compounds, namely, AT-034, AT-201 and AT-202, with a range of affinity and intrinsic activity profiles for MOP and NOP receptors, but weak ability for kappa-opioid peptide receptor (KOP) transmission, were tested. Consistent with our hypothesis based on buprenorphine's effects, results demonstrated that AT-034 and AT-201, which co-activate MOP and NOP receptors, reduced cocaine self-administration like buprenorphine. AT-202, which selectively stimulates NOP receptors, was not effective. Together, these data demonstrate that for buprenorphine, co-activation of MOP and NOP receptors is essential to reduce cocaine consumption. These results open new vistas on the treatment of cocaine addiction by developing compounds with mixed MOP/NOP agonist properties.

RationaleA major issue in the addiction field is the limited number of animal models of the voluntary induction and maintenance of alcohol dependence in outbred rats.ObjectivesTo address this issue, we developed a novel apparatus that vaporizes alcohol for 2-10min after an active nosepoke response.MethodsMale Wistar rats were allowed to self-administer alcohol vapor for 8h/day every other day for 24 sessions (escalated) or eight sessions (non-escalated). Escalated and non-escalated rats were then tested for progressive ratio responding. Anxiety-like behavior, somatic signs of withdrawal, and hyperalgesia were assessed during acute withdrawal.ResultsThe results showed that rats exhibited excellent discrimination between the active and inactive operanda (>85%), and the escalated rats quickly increased their blood alcohol levels from ~50 to >200mg% in ~6weeks. Compared with non-escalated rats, escalated rats exhibited severe addiction-like behavior, including somatic signs of withdrawal, anxiety-like behavior, hyperalgesia, and higher responding on a progressive ratio schedule of reinforcement.ConclusionsThese results demonstrate that outbred rats will voluntarily self-administer alcohol vapor to the point of dependence without the use of forced alcohol administration, sweeteners, food/water restriction, operant pretraining, or behavioral/genetic selection. This novel animal model may be particularly useful for medication development to help unveil the neuronal circuitry that underlies the voluntary induction of alcohol addiction and identify novel molecular targets that are specifically recruited after the voluntary induction and maintenance of alcohol dependence.

Opioid addiction, including addiction to heroin, has markedly increased in the past decade. The cost and pervasiveness of heroin addiction, including resistance to recovery from addiction, provide a compelling basis for developing novel therapeutic strategies. Deep brain stimulation may represent a viable alternative strategy for the treatment of intractable heroin addiction, particularly in individuals who are resistant to traditional therapies. Here we provide preclinical evidence of the therapeutic potential of high-frequency stimulation of the subthalamic nucleus (STN HFS) for heroin addiction. STN HFS prevented the re-escalation of heroin intake after abstinence in rats with extended access to heroin, an animal model of compulsive heroin taking. STN HFS inhibited key brain regions, including the substantia nigra, entopeduncular nucleus, and nucleus accumbens shell measured using brain mapping analyses of immediate-early gene expression and produced a robust silencing of STN neurons as measured using whole-cell recording ex vivo. These results warrant further investigation to examine the therapeutic effects that STN HFS may have on relapse in humans with heroin addiction.

Electronic cigarette use is particularly prevalent in adolescents, but the effects of secondhand exposure to nicotine vapor in adolescents on the propensity to develop nicotine dependence and increase nicotine self-administration in adulthood are poorly known. The present study explored the effects of nicotine vapor exposure on withdrawal-like states (hyperalgesia, spontaneous withdrawal signs, and locomotor activity) in adolescent rats and the vulnerability to acquire intravenous nicotine self-administration in adulthood. Adolescent (postnatal day 38) rats were exposed to intermittent nicotine vapor (14 h/day) for 7 consecutive days in a range of doses (0, 0.4, and 7 mg/m(3)). The rats were tested for somatic, emotional, and motivational withdrawal symptoms. When the animals reached adulthood, they were allowed to self-administer nicotine (0.03 mg/kg/0.1 ml) intravenously in operant chambers for 1 h/day for 12 consecutive days. Rats that were exposed to nicotine vapor presented moderate to severe signs of spontaneous withdrawal after the cessation of nicotine vapor. No effect on anxiety-like behavior was observed. Rats that were exposed to high levels of nicotine vapor in adolescence had lower pain thresholds and exhibited faster and higher acquisition of nicotine self-administration in adulthood. Chronic exposure to nicotine vapor in adolescent rats produces a withdrawal-like state and facilitates the acquisition of intravenous nicotine self-administration in adulthood. These results suggest that exposure of adolescents to nicotine vapor may confer higher risk of developing nicotine dependence when they become adults.

The debate about electronic cigarettes has divided healthcare professionals, policymakers, and communities. Central points of disagreement are whether vaping electronic cigarettes are addictive and whether they produce major pulmonary complications. We developed a novel model of nicotine vapor self-administration in rats and found that rats voluntarily exposed themselves to nicotine vapor to the point of reaching blood nicotine levels that are similar to humans, exhibiting both addiction-like behaviors and cardiopulmonary abnormalities. The smoking cessation drug varenicline decreased electronic cigarette self-administration. These findings confirm the addictive properties and harmful effects of nicotine vapor and identify a potential medication for the treatment of electronic cigarette addiction.One Sentence SummaryVaping nicotine-containing electronic cigarettes produces cardiopulmonary abnormalities, nicotine dependence and addiction-like behaviors, which are reduced by the smoking cessation drug varenicline.

The activation of a neuronal ensemble in the central nucleus of the amygdala (CeA) during alcohol withdrawal has been hypothesized to induce high levels of alcohol drinking in dependent rats. In the present study we describe that the CeA neuronal ensemble that is activated by withdrawal from chronic alcohol exposure contains ~80% corticotropin-releasing factor (CRF) neurons and that the optogenetic inactivation of these CeA CRF+ neurons prevents recruitment of the neuronal ensemble, decreases the escalation of alcohol drinking, and decreases the intensity of somatic signs of withdrawal. Optogenetic dissection of the downstream neuronal pathways demonstrates that the reversal of addiction-like behaviors is observed after the inhibition of CeA CRF projections to the bed nucleus of the stria terminalis (BNST) and that inhibition of the CRFCeA-BNST pathway is mediated by inhibition of the CRF-CRF1 system and inhibition of BNST cell firing. These results suggest that the CRFCeA-BNST pathway could be targeted for the treatment of excessive drinking in alcohol use disorder., Withdrawal from alcohol activates neurons in the central amygdala (CeA) and increases craving for alcohol. The authors show that these neurons predominantly express CRF and project to the BNST. Inactivation of this pathway reduces the dependence-related escalation of alcohol drinking.

Neuropeptide S (NPS) displays unique pharmacological properties and induces both anxiolytic and pro-stress/arousal activities. Previous studies performed using Wistar rats demonstrated that NPS facilitated alcohol and cocaine seeking but did not affect alcohol or cocaine consumption.Here, we investigated the effects of NPS in Marchigian Sardinian alcohol-preferring (msP) rats, a rat strain characterized by excessive alcohol consumption comorbid with heightened anxiety and depressive-like phenotypes. Specifically, we evaluated the effect of NPS on operant alcohol self-administration by msP rats compared to Wistar rats. The effect of NPS on cue-induced reinstatement of alcohol seeking in msP rats was also evaluated. Finally, using the open field test (OFT) and the elevated plus maze (EPM), we evaluated the effects of NPS on locomotor activity and anxiety.NPS reduced alcohol self-administration but did not affect cue-induced reinstatement in the msP rat. In addition, NPS induced reinstatement of extinguished alcohol seeking in Wistar rats without affecting alcohol intake. In the EPM task, NPS, in accordance with its anxiolytic activity, increased the time spent in the open arm of the arena by msP rats, although this effect was not observed in Wistar rats.These data suggest that the effect of NPS is strongly influenced by the genetic background of the animal. In Wistar rats, NPS acts as a pro-arousal agent to promote the reinstatement of alcohol seeking. However, when alcohol drinking is motivated by or associated with a state of pathological anxiety, NPS attenuates alcohol consumption and seeking due to its anxiolytic activity.

A bacterial enzyme that eats nicotine reverses addiction-like behaviors and offers a new strategy to help smokers quit., Tobacco use disorder is the leading cause of disease and preventable death worldwide, but current medications that are based on pharmacodynamics have low efficacy. Novel pharmacokinetic approaches to prevent nicotine from reaching the brain have been tested using vaccines, but these efforts have failed because antibody affinity and concentration are not sufficient to completely prevent nicotine from reaching the brain. We provide preclinical evidence of the efficacy of an enzymatic approach to reverse nicotine dependence, reduce compulsive-like nicotine intake, and prevent relapse in rats with a history of nicotine dependence. Chronic administration of NicA2-J1, an engineered nicotine-degrading enzyme that was originally isolated from Pseudomonas putida S16, completely prevented nicotine from reaching the brain and reversed somatic signs of withdrawal, hyperalgesia, and irritability-like behavior in nicotine-dependent rats with a history of escalation of nicotine self-administration. NicA2-J1 also decreased compulsive-like nicotine intake, reflected by responding despite the adverse consequences of contingent footshocks, and prevented nicotine- and stress (yohimbine)–induced relapse. These results demonstrate the efficacy of enzymatic therapy in treating nicotine addiction in advanced animal models and provide a strong foundation for the development of biological therapies for smoking cessation in humans.

BackgroundCocaine addiction is a major public health problem. Despite decades of intense research, no effective treatments are available. Both preclinical and clinical studies of drug addiction strongly suggest that the nucleus accumbens (NAcc) is a viable target for deep brain stimulation (DBS).ObjectiveAlthough previous studies have shown that DBS of the NAcc decreases cocaine seeking and reinstatement, the effects of DBS on cocaine intake in cocaine-dependent animals have not yet been investigated.MethodsRats were made cocaine-dependent by allowing them to self-administer cocaine in long-access sessions (6 h, 0.5 mg/kg/infusion). The effects of high-frequency DBS of the NAcc shell on cocaine intake was then studied. Furthermore, cocaine-induced locomotor activity, irritability-like behavior during cocaine abstinence and the levels of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits 1 and 2 (GluR1/GluA1 and GluR2/GluA2) after DBS were investigated.ResultsContrary to our expectations, DBS of the NAcc shell induced a slight increase in both cocaine self-administration and cocaine-induced locomotor activity. In addition, 18 h into cocaine withdrawal, we found that DBS decreased irritability-like behavior. We also found that DBS-induced a robust increase in both cytosolic and synaptosomal levels of GluR1, but not GluR2, specifically in the central nucleus of the amygdala but not in other brain regions.ConclusionsThese preclinical results with cocaine-dependent animals do not support high-frequency DBS of the NAcc shell as a therapeutic approach for the treatment of cocaine addiction in active cocaine users. However, the decrease in irritability-like behavior during cocaine abstinence, together with previous findings showing that DBS of the NAcc shell reduces the reinstatement of cocaine seeking in abstinent animals, warrants future investigations of DBS as a treatment for negative emotional states and craving during abstinence.HighlightsHigh-frequency DBS of the NAcc shell for the treatment of cocaine addiction is proposedDBS of the NAcc shell does not decrease cocaine intake in cocaine-dependent ratsDBS increases the level of GluR1 specifically in the central nucleus of the amygdala

Cannabis use is typically initiated during adolescence and is a significant risk factor for the development of cocaine use in adulthood. However, no preclinical studies have examined the effects of adolescent cannabinoid exposure on cocaine dependence in adulthood using the escalation model of cocaine self-administration and the assessment of negative emotional states. In the present study, we found that exposure to the cannabinoid receptor agonist WIN55,212-2 (WIN) in adolescence produced irritability-like behavior and psychomotor cross-sensitization to cocaine in adolescence. In adulthood, rats were allowed to self-administer cocaine. The acquisition of cocaine self-administration was lower in rats with adolescent WIN exposure compared with controls. However, both WIN-exposed and control rats escalated their cocaine intake at the same rate, had similar responding under a progressive-ratio schedule of reinforcement, and had similar psychomotor responses to cocaine. Interestingly, the increase in irritability-like behavior that was previously observed in adolescence after WIN exposure persisted into adulthood. Whether the persisting increase in irritability-like behavior after WIN exposure has translational relevance remains to be studied. In summary, these results suggest that psychoactive cannabinoid exposure during adolescence is unlikely to have a major effect on the escalation of cocaine intake or the development of compulsive-like responding per se in adulthood in a rat model of cocaine self-administration. However, whether the persisting irritability-like behavior may predispose an individual to mood-related impairments in adulthood or predict such impairments warrants further investigation.

GPR139 is an orphan G protein-coupled receptor (GPCR) that is expressed mainly in the brain, with the highest expression in the medial habenula. The modulation of GPR139 receptor function has been hypothesized to be beneficial in the treatment of some mental disorders, but behavioral studies have not yet provided causal evidence of the role of GPR139 in brain dysfunction. Because of the high expression of GPR139 in the habenula, a critical brain region in addiction, we hypothesized that GPR139 may play role in alcohol dependence. Thus, we tested the effect of GPR139 receptor activation using the selective, brain-penetrant receptor agonist JNJ-63533054 on addiction-like behaviors in alcohol-dependent male rats. Systemic administration of JNJ-63533054 (30 mg/kg but not 10 mg/kg, p.o.) reversed the escalation of alcohol self-administration in alcohol-dependent rats, without affecting water or saccharin intake in dependent rats or alcohol intake in nondependent rats. Moreover, systemic JNJ-63533054 administration decreased withdrawal-induced hyperalgesia, without affecting somatic signs of alcohol withdrawal. Further analysis demonstrated that JNJ-63533054 was effective only in a subgroup of dependent rats that exhibited compulsive-like alcohol drinking. Finally, site-specific microinjection of JNJ-63533054 in the habenula but not interpeduncular nucleus (IPN) reduced both alcohol self-administration and withdrawal-induced hyperalgesia in dependent rats. These results provide robust preclinical evidence that GPR139 receptor activation reverses key addiction-like behaviors in dependent animals, suggest that GPR139 may be a novel target for the treatment of alcohol use disorder, and demonstrate that GPR139 is functionally relevant in regulating mammalian behavior.

RATIONALE: The ability of nicotine to suppress body weight is cited as a factor impacting smoking initiation and the failure to quit. Self-administered nicotine in male rats suppresses weight independent of food intake, suggesting that nicotine increases energy expenditure. OBJECTIVE: The current experiment evaluated the impact of self-administered nicotine on metabolism in rats using indirect calorimetry and body composition analysis. METHODS: Adult male rats with ad libitum access to powdered standard rodent chow self-administered intravenous infusions of nicotine (60 μg/kg/infusion or saline control) in daily 1-h sessions in the last hour of the light cycle. Indirect calorimetry measured respiratory exchange ratio (RER), energy expenditure, motor activity, and food and water consumption for 22.5 h between select self-administration sessions. RESULTS: Self-administered nicotine suppressed weight gain and reduced the percent of body fat without altering the percent of lean mass, as measured by Echo MRI. Nicotine reduced RER, indicating increased fat utilization; this effect was observed prior to weight suppression. Moreover, nicotine intake did not affect motor activity or energy expenditure. Daily food intake was not altered by nicotine self-administration; however, a trend in suppression of meal size, a transient suppression of water intake, and an increase in meal frequency was observed. CONCLUSION: These data provide evidence that self-administered nicotine suppresses body weight via increased fat metabolism, independent of significant changes in feeding, activity, or energy expenditure.

A nicotine-degrading enzyme termed NicA2 was altered (NicA2-J1) through fusion of an albumin binding domain to increase its half-life. Examination of NicA2-J1 in vivo demonstrated a complete blockade of brain nicotine access, which in turn blunted nicotine's psychoactive effects. These data further support development of pharmacokinetic nicotine cessation therapeutics.

BackgroundIn humans, emotional and physical signs of withdrawal from ethanol are commonly seen. Many of these symptoms, including anxiety-like and depression-like behavior, have been characterized in animal models of ethanol dependence. One issue with several current behavioral tests measuring withdrawal in animal models is they are often not repeatable within subjects over time. Additionally, irritability, one of the most common symptoms of ethanol withdrawal in humans, has not been well characterized in animal models. The corticotropinreleasing factor (CRF)-CRF1 receptor system has been suggested to be critical for the emergence of anxiety-like behavior in ethanol dependence, but the role of this system in irritability-like behavior has not been characterized.MethodsThe present study compared the effects of chronic intermittent ethanol vapor exposure (CIE)-induced ethanol dependence on irritabilitylike behavior in rats using the bottle-brush test during acute withdrawal and protracted abstinence. Rats were trained to self-administer ethanol in operant chambers and then either left in a nondependent state or made dependent via CIE. Naive, nondependent, and dependent rats were tested for irritability-like behavior in the bottle-brush test 8 h and 2 weeks into abstinence from ethanol. A separate cohort of dependent rats was used to examine the effect of the specific CRF1 receptor antagonist R121919 on irritability-like behavior.ResultsDependent rats exhibited escalated ethanol intake compared with their own pre-CIE baseline and nondependent rats. At both time-points of abstinence, ethanol-dependent rats exhibited increased aggressive-like responses compared with naive and nondependent rats. R121919 blocked the increased irritability-like behavior in dependent rats.ConclusionsThe effect of R121919 to block increased irritability-like behavior suggests that CRF plays an important role in this behavior, similar to other negative emotional withdrawal symptoms. Quantifying and understanding the molecular basis of irritability-like behavior may yield new insights into withdrawal from ethanol and other drugs of abuse.

Nicotine, the main addictive component of tobacco, induces potentiation of brain stimulation reward, increases locomotor activity, and induces conditioned place preference. Nicotine cessation produces a withdrawal syndrome that can be relieved by nicotine replacement therapy. In the last decade, the market for electronic cigarettes has flourished, especially among adolescents. The nicotine vaporizer or electronic nicotine delivery system is a battery-operated device that allows the user to simulate the experience of tobacco smoking without inhaling smoke. The device is designed to be an alternative to conventional cigarettes that emits vaporized nicotine inhaled by the user. This report describes a procedure to vaporize nicotine in the air to produce blood nicotine levels in rodents that are clinically relevant to those that are observed in humans and produce dependence. We also describe how to construct the apparatus to deliver nicotine vapor in a stable, reliable, and consistent manner, as well as how to analyze air for nicotine content. © 2017 by John Wiley & Sons, Inc.

Relapse to opioids is often driven by the avoidance of the aversive states of opioid withdrawal. We recently demonstrated that activation of peroxisome proliferator-activated receptor gamma (PPARγ) by pioglitazone reduces the motivation for heroin and attenuates its rewarding properties. However, the role of PPARγ in withdrawal and other forms of relapse to heroin is unknown. To further address this issue, we investigated the role of PPARγ on the development and expression of morphine withdrawal in mice and the effect of pioglitazone on several forms of heroin relapse in rats. We induced physical dependence to morphine in mice by injecting morphine twice daily for 6 days. Withdrawal syndrome was precipitated on day 6 with an injection of naloxone. In addition, different groups of rats were trained to self-administer heroin and, after the extinction, the relapse was elicited by cues, priming, or stress. The effect of different doses of pioglitazone was tested on these different paradigms. Data show that chronic and acute administration of pioglitazone attenuates morphine withdrawal symptoms, and these effects are mediated by activation of PPARγ receptors. Activation of PPARγ by pioglitazone also abolishes yohimbine-induced reinstatement of heroin seeking and reduces heroin-induced reinstatement, while it does not affect cue-induced relapse. These findings provide new insights on the role of PPARγ on opioid dependence and suggest that pioglitazone may be useful for the treatment of opioid withdrawal in opioid-addicted individuals.

The nociceptin (NOP) receptor is a G-protein-coupled receptor whose natural ligand is the NOP/orphanin FQ (N/OFQ) peptide. Evidence from pharmacological studies suggests that the N/OFQ system is implicated in the regulation of several addiction-related phenomena, such as drug intake, withdrawal, and relapse. Here, to further explore the role of NOP system in addiction, we used NOP (−/−) rats to study the motivation for cocaine, heroin, and alcohol self-administration in the absence of N/OFQ function. Conditioned place preference (CPP) and saccharin (0.2% w/v) self-administration were also investigated. Results showed that NOP (−/−) rats self-administer less cocaine (0.25, 0.125, or 0.5 mg/infusion) both under a fixed ratio 1 and a progressive ratio schedule of reinforcement compared with wild-type (Wt) controls. Consistently, cocaine (10 mg/kg, i.p.) was able to induce CPP in Wt but not in NOP (−/−). When NOP (−/−) rats were tested for heroin (20 μg/infusion) and ethanol (10% v/v) self-administration, they showed significantly lower drug intake compared with Wt. Conversely, saccharin self-administration was not affected by NOP deletion, excluding the possibility of nonspecific learning deficits or generalized disruption of reward mechanisms in NOP (−/−) rats. These findings were confirmed with pharmacological experiments using two selective NOP antagonists, SB-612111 and LY2817412. Both drugs attenuated alcohol self-administration in Wt rats but not in NOP (−/−) rats. In conclusion, our results demonstrate that genetic deletion of NOP receptors confers resilience to drug abuse and support a role for NOP receptor antagonism as a potential treatment option for drug addiction.

BACKGROUND: Environmental conditioning is a major trigger for relapse in abstinent addicts. We showed that activation of the neuropeptide S (NPS) system exacerbates reinstatement vulnerability to cocaine and alcohol via stimulation of the hypocretin-1/orexin-A (Hcrt-1/Ox-A) system. METHODS: Combining pharmacologic manipulations with immunohistochemistry techniques, we sought to determine how NPS and Hcrt-1/Ox-A systems interact to modulate reinstatement of alcohol seeking in rats. RESULTS: Intrahypothalamic injection of NPS facilitated discriminative cue-induced reinstatement of alcohol seeking. This effect was blocked by the selective Hcrt-1/Ox-A antagonist SB334867 microinjected into the hypothalamic paraventricular nucleus (PVN) or into the bed nucleus of the stria terminalis (BNST) but not into the ventral tegmental area or the locus coeruleus. Combining double labeling and confocal microscopy analyses, we found that NPScontaining axons are in close apposition to hypothalamic Hcrt-1/Ox-A positive neurons, a significant proportion of which express NPS receptors, suggesting a direct interaction between the two systems. Retrograde tracing experiments showed that intra-PVN or intra-BNST red fluorobead unilateral injection labeled bilaterally Hcrt-1/Ox-A somata, suggesting that NPS could recruit two distinct neuronal pathways. Confirming this assumption, intra-BNST or PVN Hcrt-1/Ox-A injection enhanced alcohol seeking similarly to hypothalamic NPS injection but to a lesser degree. CONCLUSIONS: Results suggest that the Hcrt-1/Ox-A neurocircuitry mediating the facilitation of cue-induced reinstatement by NPS involves structures critically involved in stress regulation such as the PVN and the BNST. These findings open to the tempting hypothesis of a role of the NPS system in modulating the interactions between stress and environmental conditioning factors in drug relapse.

The GABAergic system in the central amygdala (CeA) plays a major role in ethanol dependence and the anxiogenic-like response to ethanol withdrawal. A large body of evidence shows that Nociceptin/Orphanin FQ (N/OFQ) regulates ethanol intake and anxiety-like behavior. In the rat, ethanol significantly augments CeA GABA release, whereas N/OFQ diminishes it. Using electrophysiological techniques in an in vitro slice preparation, in this study we investigated the effects of a nonpeptidergic NOP receptor agonist, MT-7716 [(R)-2-3-[1-(Acenaphthen-1-yl)piperidin-4-yl]-2-oxo-2,3-dihydro-1H-benzimidazol-1-yl-N-methylacetamide hydrochloride hydrate], and its interaction with ethanol on GABAergic transmission in CeA slices of naïve rats. We found that MT-7716 dose-dependently (100-1000 nM) diminished evoked GABAA receptor-mediated inhibitory postsynaptic potentials (IPSPs) and increased paired-pulse facilitation (PPF) ratio of these evoked IPSPs, suggesting a presynaptic site of action of the MT-7716 by decreasing GABA release at CeA synapses. The presynaptic action of MT-7716 was also supported by the significant decrease in the frequency of miniature inhibitory postsynaptic currents (mIPSCs) induced by the nociceptin receptor (NOP) agonist. Interestingly, MT-7716 prevented the ethanol-induced augmentation of evoked IPSPs. A putative selective NOP antagonist, [Nphe1]Nociceptin(1-13)NH2, totally prevented the MT-7716-induced inhibition of IPSP amplitudes indicating that MT-7716 exerts its effect through NOPs. These data provide support for an interaction between the nociceptin and GABAergic systems in the CeA and for the anti-alcohol properties of the NOP activation. The development of a synthetic nonpeptidergic NOP receptor agonist such as MT-7716 may represent a useful therapeutic target for alcoholism.