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Rationale One of the most commonly cited reasons for chronic cannabis use is to cope with stress. Consistent with this, cannabis users have shown reduced emotional arousal and dampened stress reactivity in response to negative imagery. Objectives To our knowledge, the present study represents the first to examine the effects of an acute stress manipulation on subjective stress and salivary cortisol in chronic cannabis users compared to non-users. Methods Forty cannabis users and 42 non-users were randomly assigned to complete either the stress or no stress conditions of the Maastricht Acute Stress Test (MAST). The stress condition of the MAST manipulates both physiological (placing hand in ice bath) and psychosocial stress (performing math under conditions of social evaluation). Participants gave baseline subjective stress ratings before, during, and after the stress manipulation. Cortisol was measured from saliva samples obtained before and after the stress manipulation. Further, cannabis cravings and symptoms of withdrawal were measured. Results Subjective stress ratings and cortisol levels were significantly higher in non-users in the stress condition relative to non-users in the no stress condition. In contrast, cannabis users demonstrated blunted stress reactivity; specifically, they showed no increase in cortisol and a significantly smaller increase in subjective stress ratings. The stress manipulation had no impact on cannabis users’ self-reported cravings or withdrawal symptoms. Conclusion Chronic cannabis use is associated with blunted stress reactivity. Future research is needed to determine whether this helps to confer resiliency or vulnerability to stress-related psychopathology as well as the mechanisms underlying this effect.

The psychostimulants, morphine and methamphetamine are well known drugs of abuse that induce brain pathology and/or neurodegeneration resulting in a huge burden on our society. The possible mechanisms of psychostimulants induced neuropathology and neurodegeneration are still not well known. The drugs of abuse results in profound hyperthermia and widespread alterations in neurochemical metabolism in the central nervous system (CNS). It appears that psychostimulants induced hyperthermia and/or release of neurochemicals influence the blood-brain barrier (BBB) dysfunction leading to brain pathology. The drugs of abuse also induce oxidative stress resulting in generation of free radicals and lipid peroxidation. Thus, further research is needed to understand the basic function of BBB disruption and temperature regulation by psychostimulants and to modify them pharmacologically to attenuate brain dysfunction and neuropathology. This review is focused on the problems of morphine and methamphetamine induced hyperthermia and their effects on breakdown of the BBB function leading to brain damage. Works done in our laboratory suggest that hyperthermia caused by these drugs is responsible for BBB disruption and neurodegeneration. This hypothesis is further supported by our observation that pretreatment with a portent antioxidant compound H-290/51 attenuates the BBB disruption and induces marked neuroprotection following morphine induced withdrawal and methamphetamine induced neurotoxicity. The possible mechanisms and functional significance of these findings are discussed.

Objective: Second-generation antipsychotics (SGAs) cause weight gain and cardiometabolic abnormalities in children and adolescents. Less well-investigated is the outcome of these adverse events following SGA discontinuation, which we examined. Methods: Medically healthy 7 to 17-year-old patients treated with risperidone for ≥6 months were enrolled and returned for follow-up, 1.5 years later. Treatment history was extracted from the medical and pharmacy records. Anthropometric and laboratory measurements were obtained at each research visit. Multivariable linear regression analysis and Fisher's exact test were used to compare participants who remained on risperidone at follow-up (Risp Cont Group) with those who had discontinued SGA treatment (SGA Disc Group) and those who had switched to another SGA (SGA Cont Group). Correlational analyses examined the association between change in age-sex specific body mass index (BMI) z score between study entry and follow-up and change in cardiometabolic outcomes. Results: The sample consisted of 101 participants (93% male) with a mean age of 11.7±2.6 years at study entry. The majority had an externalizing disorder and received 0.03±0.02 mg/kg/day of risperidone, for 2.5±1.6 years. At follow-up, 18% (n=18) were in the SGA Disc Group and 9% (n=9) were in the SGA Cont Group. BMI z score decreased in the SGA Disc Group, remained unchanged in the Risp Cont Group (n=74), and increased in the SGA Cont Group. Importantly, the change in BMI z score between study entry and follow-up was significantly correlated with the change in systolic and diastolic blood pressure z scores, heart rate, waist circumference, percent body fat, inflammatory markers, fasting total insulin, homeostatic model assessment insulin resistance index (HOMA-IR), C-peptide, total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol, triglycerides, triglycerides/HDL ratio, and leptin. Conclusions: Following several years of treatment, risperidone discontinuation is associated with a reversal of the excessive weight gain, mediated by a negative energy balance, and a corresponding improvement in cardiometabolic parameters.

Rationale The available treatments for alcoholism are only modestly effective, and patients vary widely in their treatment response. Quetiapine, an atypical antipsychotic medication with antagonist activity at D1 and D2, 5-HT 1A and 5-HT 2A , H 1 , and α1 and α2 receptors was shown to promote abstinence, reduce drinking days, and reduce heavy drinking days in a 12-week double-blind placebo-controlled trial. Objective Although quetiapine represents one of the promising pharmacotherapies for the treatment of alcoholism, its mechanisms of action are poorly understood. The objective of this study is to elucidate the biobehavioral mechanisms of action of quetiapine for alcoholism, by examining its effects on subjective intoxication and craving. Method A total of 20 non-treatment-seeking alcohol-dependent individuals were randomized to one of the following conditions in a double-blind, placebo-controlled design: (1) quetiapine (400 mg/day); or (2) matched placebo. Participants were on the target medication dose (or matched placebo) for 4 weeks during which they completed weekly assessments of drinking, sleep, mood, and anxiety. Participants completed two counterbalanced intravenous placebo-alcohol administration sessions as well as cue-reactivity assessments. Results Analyses revealed a significant effect of quetiapine in reducing craving during the alcohol administration, the alcohol cue-exposure, and the weekly reports of alcohol craving. Quetiapine was also found to reduce subjective intoxication and alcohol-induced sedation during the alcohol administration paradigm. Conclusions This study contributes critical new information about mechanisms of response to quetiapine for alcoholism, which, in turn, can inform larger-scale studies and ultimately, clinical practice.

Hyperactive amygdala functioning may underlie emotional dysregulation during smoking abstinence and represents one neurobiological target for pharmacological cessation aids. Available pharmacotherapies (e.g., nicotine replacement and varenicline) aid only a subset of individuals with smoking cessation and therefore elucidating the neurobiological impact of these medications is critical to expedite improved interventions. In a fMRI study employing a within-subject, double-blind, placebo-controlled design, we assessed task performance and amygdala functioning during an emotional face matching paradigm following administration of nicotine and varenicline to 24 abstinent smokers and 20 nonsmokers. All participants underwent ~17days of varenicline and placebo pill administration and were scanned, on different days under each condition, wearing a transdermal nicotine or placebo patch. During the amygdala reactivity paradigm, nicotinic acetylcholine receptor (nAChR) stimulation by nicotine and varenicline decreased reaction time (RT) in abstinent smokers but not in nonsmokers. When considering all smokers as a single homogenous group, no drug-induced effects on amygdala reactivity were detected. However, in an exploratory analysis we parsed participants into subgroups according to individual differences in the propensity to demonstrate stable performance augmentation following nAChR stimulation (stable RT-improvers [SI] vs. variable RT-improvers [VI]). Using this exploratory approach, drugs appeared to modulate amygdala reactivity in only one smoker subgroup but not in either nonsmoker subgroup. Specifically, in the SI-smoker cohort abstinence-induced elevated amygdala reactivity was down-regulated by nAChR stimulation. In contrast, varenicline and nicotine did not modulate amygdala functioning in the VI-smoker cohort who displayed moderate levels of amygdala reactivity in the absence of drug administration. These results suggest that pharmacotherapies most robustly dampened amygdala functioning in smokers appearing susceptible to abstinence-induced effects. Such findings provide a step towards fractionating the smoker phenotype by discrete neurobiological characteristics. ► Varenicline attenuates nicotine's impact on heart rate in both smokers and nonsmokers. ► Varenicline and nicotine augment task performance in smokers but not nonsmokers. ► Drugs dampen amygdala reactivity in smokers susceptible to abstinence-induced effects.

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 CRF CeA-BNST pathway is mediated by inhibition of the CRF-CRF 1 system and inhibition of BNST cell firing. These results suggest that the CRF CeA-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.

Fentanyl is a powerful painkiller that elicits euphoria and positive reinforcement 1 . Fentanyl also leads to dependence, defined by the aversive withdrawal syndrome, which fuels negative reinforcement 2 , 3 (that is, individuals retake the drug to avoid withdrawal). Positive and negative reinforcement maintain opioid consumption, which leads to addiction in one-fourth of users, the largest fraction for all addictive drugs 4 . Among the opioid receptors, µ-opioid receptors have a key role 5 , yet the induction loci of circuit adaptations that eventually lead to addiction remain unknown. Here we injected mice with fentanyl to acutely inhibit γ-aminobutyric acid-expressing neurons in the ventral tegmental area (VTA), causing disinhibition of dopamine neurons, which eventually increased dopamine in the nucleus accumbens. Knockdown of µ-opioid receptors in VTA abolished dopamine transients and positive reinforcement, but withdrawal remained unchanged. We identified neurons expressing µ-opioid receptors in the central amygdala (CeA) whose activity was enhanced during withdrawal. Knockdown of µ-opioid receptors in CeA eliminated aversive symptoms, suggesting that they mediate negative reinforcement. Thus, optogenetic stimulation caused place aversion, and mice readily learned to press a lever to pause optogenetic stimulation of CeA neurons that express µ-opioid receptors. Our study parses the neuronal populations that trigger positive and negative reinforcement in VTA and CeA, respectively. We lay out the circuit organization to develop interventions for reducing fentanyl addiction and facilitating rehabilitation. Experiments using fentanyl treatment of mice show that µ-opioid receptors mediate positive reinforcement in the ventral tegmental area and negative reinforcement in central amygdala, thereby identifying the circuits that lead to opioid addiction.

The release of ATP from spinal microglia via pannexin-1 channels is required for withdrawal symptoms after termination of chronic opioid treatment in rodents, and pharmacological blockade of pannexin-1 channels reduces the severity of withdrawal without affecting opiate analgesia. Opiates are essential for treating pain, but termination of opiate therapy can cause a debilitating withdrawal syndrome in chronic users. To alleviate or avoid the aversive symptoms of withdrawal, many of these individuals continue to use opiates 1 , 2 , 3 , 4 . Withdrawal is therefore a key determinant of opiate use in dependent individuals, yet its underlying mechanisms are poorly understood and effective therapies are lacking. Here, we identify the pannexin-1 (Panx1) channel as a therapeutic target in opiate withdrawal. We show that withdrawal from morphine induces long-term synaptic facilitation in lamina I and II neurons within the rodent spinal dorsal horn, a principal site of action for opiate analgesia. Genetic ablation of Panx1 in microglia abolished the spinal synaptic facilitation and ameliorated the sequelae of morphine withdrawal. Panx1 is unique in its permeability to molecules up to 1 kDa in size and its release of ATP 5 , 6 . We show that Panx1 activation drives ATP release from microglia during morphine withdrawal and that degrading endogenous spinal ATP by administering apyrase produces a reduction in withdrawal behaviors. Conversely, we found that pharmacological inhibition of ATP breakdown exacerbates withdrawal. Treatment with a Panx1-blocking peptide ( 10 panx) or the clinically used broad-spectrum Panx1 blockers, mefloquine or probenecid, suppressed ATP release and reduced withdrawal severity. Our results demonstrate that Panx1-mediated ATP release from microglia is required for morphine withdrawal in rodents and that blocking Panx1 alleviates the severity of withdrawal without affecting opiate analgesia.

Although converging lines of evidence suggest that nicotine and mood are related at a fundamental biological level, this link has not been reliably demonstrated in laboratory studies. In this study, startle probe methodology was used to examine the effects of nicotine administration and deprivation on emotional processes associated with motivation. Smokers (N=115) completed four laboratory sessions crossing deprivation (12-hr deprived vs. nondeprived) with nicotine spray (active vs. placebo). Participants viewed affective pictures (positive, negative, neutral) and pictures involving cigarette cues, while startle probes were administered. Deprivation decreased startle responding to cigarette cues, suggesting an activation of appetitive processes. Nicotine administration suppressed overall startle responding during deprivation. In addition, during deprivation, random exposure to negative stimuli over two blocks of trials resulted in decreased adaptation of the startle response, suggesting that some sensitization to negative emotional cues may take place during nicotine withdrawal. These effects are consistent with formulations of addiction, stressing that withdrawal may both increase the reinforcement salience of smoking stimuli and decrease habituation to negative emotional stimuli.

It has been demonstrated that opioid agonists that preferentially act at μ-opioid receptors to activate G protein signaling over βarrestin2 recruitment produce antinociception with less respiratory suppression. However, most of the adverse effects associated with opioid therapeutics are realized after extended dosing. Therefore, we tested the onset of tolerance and dependence, and assessed for neurochemical changes associated with prolonged treatment with the biased agonist SR-17018. When chronically administered to mice, SR-17018 does not lead to hot plate antinociceptive tolerance, receptor desensitization in periaqueductal gray, nor a super-sensitization of adenylyl cyclase in the striatum, which are hallmarks of opioid neuronal adaptations that are seen with morphine. Interestingly, substitution with SR-17018 in morphine-tolerant mice restores morphine potency and efficacy, whereas the onset of opioid withdrawal is prevented. This is in contrast to buprenorphine, which can suppress withdrawal, but produces and maintains morphine antinociceptive tolerance. Biased agonists of this nature may therefore be useful for the treatment of opioid dependence while restoring opioid antinociceptive sensitivity.