Is impulsivity related to attentional bias in cigarette smokers? An exploration across levels of nicotine dependency and deprivation.

Research has largely focused on how attentional bias to smoking-related cues and impulsivity independently influence the development and maintenance of cigarette smoking, with limited exploration of the relationship between these mechanisms. The current experiments systematically assessed relationships between multiple dimensions of impulsivity and attentional bias, at different stages of attention, in smokers varying in nicotine dependency and deprivation. Nonsmokers (NS; n  = 26), light-satiated smokers (LS; n  = 25), heavy-satiated smokers (HS; n  = 23) and heavy 12-hour nicotine-deprived smokers (HD; n  = 30) completed the Barratt Impulsivity Scale, delayed discounting task, stop-signal task, information sampling task and a visual dot-probe assessing initial orientation (200 ms) and sustained attention (2000 ms) toward smoking-related cues. Sustained attention to smoking-related cues was present in both HS and LS, while initial orientation bias was only evident in HS. HS and LS also had greater levels of trait motor and nonplanning impulsivity and heightened impulsive choice on the delay discounting task compared with NS, while heightened trait attentional impulsivity was only found in HS. In contrast, in HD, nicotine withdrawal was associated with no attentional bias but heightened reflection impulsivity, poorer inhibitory control and significantly lower levels of impulsive choice relative to satiated smokers. Trait and behavioral impulsivity were not related to the extent of attentional bias to smoking-related cues at any stage of attention, level of nicotine dependency or state of deprivation. Findings have both clinical and theoretical implications, highlighting the unique and independent roles impulsivity and attentional bias may play at different stages of the nicotine addiction cycle.

Reliability and validity of the Estonian version of the Clinical Institute of Withdrawal Assessment for Alcohol scale.

AIMS: Our aim was to adapt the Clinical Institute of Withdrawal Assessment for Alcohol scale (CIWA-Ar) into Estonian and test its reliability and validity. METHODS: A total of 72 patients with alcohol withdrawal syndrome participated in the study. In order to assess the interrater reliability, at first assessment the CIWA-Ar was simultaneously completed by two nurses. In order to assess the sensitivity of the CIWA-Ar to the changes in the severity of the withdrawal syndrome, as well as its correlations to several indices characterizing the subjects' current condition, the CIWA-Ar, the Clinical Global Impression Severity subscale (CGI-S), the visual analogue scales for the assessment of the general feeling of malaise, anxiety and depression were filled in and the vital signs were measured at inclusion, in 4 h and after the withdrawal syndrome had been resolved. RESULTS: The intraclass correlation coefficient (ICC) for the Estonian version of the CIWA-Ar total score, used as an indicator of interrater reliability, was excellent. The CIWA-Ar had significant correlations with the psychiatrists' CGI-S ratings of the severity of the patient's condition at all assessment points. Significant correlations were also found between CIWA-Ar and patients' self-ratings, the highest correlations found with self-rated anxiety and general feeling of malaise. CIWA-Ar total score did not correlate with simultaneously measured heart rate, systolic and diastolic blood pressure at the first assessment. At the second assessment, heart rate had a significant correlation with the CIWA-Ar total score. CONCLUSION: Our study provides confirmation that the CIWA-Ar tool is well applicable in the Estonian language and culture setting.

Withdrawal from cocaine conditioning progressively alters AMPA receptor-mediated transmission in the ventral hippocampus.

Drugs of abuse, such as cocaine, produce aberrant changes in synaptic transmission and plasticity that emerge throughout withdrawal. One region of the brain that displays a high degree of synaptic plasticity, as well as connectivity with mesolimbic structures such as the nucleus accumbens, is the ventral hippocampus (vH). Here, we investigated the effects of an escalating cocaine dosing schedule on vH CA1 excitatory transmission by measuring place preference and recording excitatory postsynaptic currents (EPSCs) at three different withdrawal time points: withdrawal day (WD) 2, 9 or 28. Behaviourally, this escalating cocaine-conditioning protocol was capable of producing conditioned place preference that persisted through WD28. Physiologically, cocaine conditioning produced an increase in vH excitatory transmission on WD2 that appeared to be the result of an increase in calcium-impermeable (CI)-AMPA receptor density. Excitatory transmission was still enhanced in cocaine-treated animals on WD9; however, a significant increase in the contribution of calcium-permeable (CP)-AMPA receptors to EPSCs was detected as compared with WD2. By WD28, these CP-AMPA receptors provided a major contribution to vH CA1 excitatory transmission, resulting in synaptic responses distinct from WD2 and WD9. Taken together, these results highlight progressive changes in vH synaptic transmission during withdrawal that may enhance cocaine contextual associations.

Cardiorespiratory anomalies and increased brainstem microglia in a rat model of neonatal opioid withdrawal syndrome.

Infants born with neonatal opioid withdrawal syndrome (NOWS) can display abnormal cardiorespiratory patterns including tachypnea, tachycardia, and impaired ventilatory responses to hypoxia (HVR) and hypercapnia (HCVR). Chronic morphine exposure is associated with increased midbrain microglial expression. Using a rat model of pre- and post-natal morphine exposure, we assessed cardiorespiratory features of NOWS (resting tachycardia and tachypnea) including the attenuated HVR and HCVR and whether they are associated with increased brainstem microglia expression. Pregnant rats (dams) received twice-daily subcutaneous injections of morphine (5 mg/kg) during the third (last) week of pregnancy to simulate 3rd trimester in utero opioid exposure. Offspring then received once-daily subcutaneous injections of morphine (0.5 mg/kg) until postnatal (P) day P10 days of age to simulate postnatal morphine therapy. Cardiorespiratory responses were assessed 24 h later (P11 days) following spontaneous withdrawal. Compared to saline-treated pups, morphine-exposed offspring exhibited tachycardia and tachypnea as well as an attenuated HVR and HCVR. Microglial cell counts were increased in the nucleus tractus solitarius (nTS), dorsal motor nucleus of the vagus (DMNV) and nucleus ambiguous (NAamb), but not the retrapezoid nucleus (RTN) or the non-cardiorespriatory region, the cuneate nucleus (CN). These data suggest that the cardiorespiratory features and autonomic dysregulation in NOWS infants may be associated with altered microglial function in specific brainstem cardiorespiratory control regions.

Prevention of glutamate excitotoxicity in lateral habenula alleviates ethanol withdrawal-induced somatic and behavioral effects in ethanol dependent mice.

Ethanol withdrawal commonly leads to anxiety-related disorder, a central factor toward negative reinforcement leading to relapse. The lateral habenula (LHb), an epithalamic nucleus, has emerged to be critical for both reward and aversion processing. Recent studies have also implicated the hyperactivity of LHb, adding to the emergence of negative emotional states during withdrawal from addictive drugs. Herein, we have studied the effects of glutamate transporter inhibitor (PDC), GluN2B-containing NMDAR antagonist (Ro25-6981), and intracellular calcium chelator (BAPTA-AM) injection in LHb on ethanol withdrawal symptoms. We found that ethanol 4 g/kg 20 % w/v intragastric (i.g.) for 10 days followed by 24 h of withdrawal showed a significant increase in somatic signs characterized by vocalization, shaking, and scratching. It also increased locomotor activity and anxiety-like behavior, collectively showing expression of ethanol withdrawal symptoms. The intra-LHb administration of PDC (0.5 ng) worsened the effect of ethanol withdrawal, whereas Ro25-6981 (2 and 4 ng) and BAPTA-AM (6.5 and 13 ng) significantly reversed ethanol withdrawal-induced behavior evident by a decrease in somatic signs, locomotor activity, and anxiety-like behavior. Further, pretreatment of Ro25-6981 and BAPTA-AM reduced the neuronal loss, whereas PDC increased it compared to the vehicle-treated group, as evidenced by NeuN staining. Altogether, our results suggest that increased glutamate, GluN2B activation, and likely calcium increase indicative of glutamate excitotoxicity-induced neuronal loss in LHb possibly endorse the emergence of ethanol withdrawal symptoms, while their inhibition might help in alleviating the ethanol withdrawal symptoms.

Disentangling craving- and valence-related brain responses to smoking cues in individuals with nicotine use disorder.

Tobacco smoking is one of the leading causes of preventable death and disease worldwide. Most smokers want to quit, but relapse rates are high. To improve current smoking cessation treatments, a better understanding of the underlying mechanisms of nicotine dependence and related craving behaviour is needed. Studies on cue-driven cigarette craving have been a particularly useful tool for investigating the neural mechanisms of drug craving. Here, functional neuroimaging studies in humans have identified a core network of craving-related brain responses to smoking cues that comprises of amygdala, anterior cingulate cortex, orbitofrontal cortex, posterior cingulate cortex and ventral striatum. However, most functional Magnetic Resonance Imaging (fMRI) cue-reactivity studies do not adjust their stimuli for emotional valence, a factor assumed to confound craving-related brain responses to smoking cues. Here, we investigated the influence of emotional valence on key addiction brain areas by disentangling craving- and valence-related brain responses with parametric modulators in 32 smokers. For one of the suggested key regions for addiction, the amygdala, we observed significantly stronger brain responses to the valence aspect of the presented images than to the craving aspect. Our results emphasize the need for carefully selecting stimulus material for cue-reactivity paradigms, in particular with respect to emotional valence. Further, they can help designing future research on teasing apart the diverse psychological dimensions that comprise nicotine dependence and, therefore, can lead to a more precise mapping of craving-associated brain areas, an important step towards more tailored smoking cessation treatments.

Adenosine Monophosphate-activated Protein Kinase (AMPK) in serotonin neurons mediates select behaviors during protracted withdrawal from morphine in mice.

Serotonin neurotransmission has been implicated in behavior deficits that occur during protracted withdrawal from opioids. In addition, studies have highlighted multiple pathways whereby serotonin (5-HT) modulates energy homeostasis, however the underlying metabolic effects of opioid withdrawal have not been investigated. A key metabolic regulator that senses the energy status of the cell and regulates fuel availability is Adenosine Monophosphate-activated Protein Kinase (AMPK). To investigate the interaction between cellular metabolism and serotonin in modulating protracted abstinence from morphine, we depleted AMPK in serotonin neurons. Morphine exposure via drinking water generates dependence in these mice, and both wildtype and serotonergic AMPK knockout mice consume similar amounts of morphine with no changes in body weight. Serotonergic AMPK contributes to baseline differences in open field and social interaction behaviors and blocks abstinence induced reductions in immobility following morphine withdrawal in the tail suspension test. Lastly, morphine locomotor sensitization is blunted in mice lacking AMPK in serotonin neurons. Taken together, our results suggest serotonergic AMPK mediates both baseline and protracted morphine withdrawal-induced behaviors.

A limited access oral oxycodone paradigm produces physical dependence and mesocorticolimbic region-dependent increases in DeltaFosB expression without preference.

The abuse of oral formulations of prescription opioids has precipitated the current opioid epidemic. We developed an oral oxycodone consumption model consisting of a limited access (4 h) two-bottle choice drinking in the dark (TBC-DID) paradigm and quantified dependence with naloxone challenge using mice of both sexes. We also assessed neurobiological correlates of withdrawal and dependence elicited via oral oxycodone consumption using immunohistochemistry for DeltaFosB (ΔFosB), a transcription factor described as a molecular marker for drug addiction. Neither sex developed a preference for the oxycodone bottle, irrespective of oxycodone concentration, bottle position or prior water restriction. Mice that volitionally consumed oxycodone exhibited hyperlocomotion in an open field test and supraspinal but not spinally-mediated antinociception. Both sexes also developed robust, dose-dependent levels of opioid withdrawal that was precipitated by the opioid antagonist naloxone. Oral oxycodone consumption followed by naloxone challenge led to mesocorticolimbic region-dependent increases in the number of ΔFosB expressing cells. Naloxone-precipitated withdrawal jumps, but not the oxycodone bottle % preference, was positively correlated with the number of ΔFosB expressing cells specifically in the nucleus accumbens shell. Thus, limited access oral consumption of oxycodone produced physical dependence and increased ΔFosB expression despite the absence of opioid preference. Our TBC-DID paradigm allows for the study of oral opioid consumption in a simple, high-throughput manner and elucidates the underlying neurobiological substrates that accompany opioid-induced physical dependence.

Extended amygdala, conditioned withdrawal and memory consolidation.

Opioid withdrawal can be associated to environmental cues through classical conditioning. Exposure to these cues can precipitate a state of conditioned withdrawal in abstinent subjects, and there are suggestions that conditioned withdrawal can perpetuate the addiction cycle in part by promoting the storage of memories. This review discusses evidence supporting the hypothesis that conditioned withdrawal facilitates memory consolidation by activating a neurocircuitry that involves the extended amygdala. Specifically, the central amygdala, the bed nucleus of the stria terminalis, and the nucleus accumbens shell interact functionally during withdrawal, mediate expression of conditioned responses, and are implicated in memory consolidation. From this perspective, the extended amygdala could be a neural pathway by which drug-seeking behaviour performed during a state of conditioned withdrawal is more likely to become habitual and persistent.

Amygdalar κ-opioid receptor-dependent upregulating glutamate transporter 1 mediates depressive-like behaviors of opioid abstinence.

Opiates produce a strong rewarding effect, but abstinence from opiate use emerges with severe negative emotions. Depression is one of the most frequent emotion disorders associated with opiate abstinence, which is thought to be a main cause for relapse. However, neurobiological bases of such an aversive emotion processing are poorly understood. Here, we find that morphine abstinence activates κ-opioid receptors (KORs) by increasing endogenous KOR ligand dynorphin expression in the amygdala, which in turn facilitates glutamate transporter 1 (GLT1) expression by activation of p38 mitogen-activated protein kinase (MAPK). Upregulation of GLT1 expression contributes to opiate-abstinence-elicited depressive-like behaviors through modulating amygdalar glutamatergic inputs to the nucleus accumbens (NAc). Intra-amygdala injection of GLT1 inhibitor DHK or knockdown of GLT1 expression in the amygdala significantly suppresses morphine-abstinence-induced depressive-like behaviors. Pharmacological and pharmacogenetic activation of amygdala-NAc projections prevents morphine-abstinence-induced behaviors. Overall, our study provides key molecular and circuit insights into the mechanisms of depression associated with opiate abstinence.

Research Needs for Inpatient Management of Severe Alcohol Withdrawal Syndrome: An Official American Thoracic Society Research Statement.

Background: Severe alcohol withdrawal syndrome (SAWS) is highly morbid, costly, and common among hospitalized patients, yet minimal evidence exists to guide inpatient management. Research needs in this field are broad, spanning the translational science spectrum. Goals: This research statement aims to describe what is known about SAWS, identify knowledge gaps, and offer recommendations for research in each domain of the Institute of Medicine T0-T4 continuum to advance the care of hospitalized patients who experience SAWS. Methods: Clinicians and researchers with unique and complementary expertise in basic, clinical, and implementation research related to unhealthy alcohol consumption and alcohol withdrawal were invited to participate in a workshop at the American Thoracic Society 2019 International Conference. The committee was subdivided into four groups on the basis of interest and expertise: T0-T1 (basic science research with translation to humans), T2 (research translating to patients), T3 (research translating to clinical practice), and T4 (research translating to communities). A medical librarian conducted a pragmatic literature search to facilitate this work, and committee members reviewed and supplemented the resulting evidence, identifying key knowledge gaps. Results: The committee identified several investigative opportunities to advance the care of patients with SAWS in each domain of the translational science spectrum. Major themes included 1) the need to investigate non-γ-aminobutyric acid pathways for alcohol withdrawal syndrome treatment; 2) harnessing retrospective and electronic health record data to identify risk factors and create objective severity scoring systems, particularly for acutely ill patients with SAWS; 3) the need for more robust comparative-effectiveness data to identify optimal SAWS treatment strategies; and 4) recommendations to accelerate implementation of effective treatments into practice. Conclusions: The dearth of evidence supporting management decisions for hospitalized patients with SAWS, many of whom require critical care, represents both a call to action and an opportunity for the American Thoracic Society and larger scientific communities to improve care for a vulnerable patient population. This report highlights basic, clinical, and implementation research that diverse experts agree will have the greatest impact on improving care for hospitalized patients with SAWS.

Nonclinical evaluation of abuse liability of the dual orexin receptor antagonist lemborexant.

Lemborexant is a dual orexin receptor antagonist (DORA) approved in multiple countries including the United States, Japan, Canada and Australia for the treatment of adults with insomnia. As required for marketing approval of new compounds with central nervous system activity with sedating effects, the abuse potential of lemborexant was assessed in accordance with regulatory guidelines, which included three nonclinical studies. These assessments comprised physical dependence and drug discrimination studies in rats and a self-administration study in rhesus monkeys. There was no evidence of withdrawal signs following abrupt drug discontinuation, indicating that lemborexant does not induce physical dependence. In the drug discrimination study, lemborexant at doses up to 1000 mg/kg administered orally did not cross-generalize to the zolpidem training stimulus, although another DORA included in the same experiment, suvorexant, showed partial generalization with zolpidem. In rhesus monkeys, lemborexant treatment did not induce any gross behavioral changes, and there was no increase in self-administration rates compared with control, indicative of a lack of reinforcing effects of lemborexant. Collectively, these nonclinical studies support the position that lemborexant, which has been placed in Schedule IV by the United States Drug Enforcement Administration, has a low risk of abuse in humans.

Orbitofrontal cortex and dorsal striatum functional connectivity predicts incubation of opioid craving after voluntary abstinence.

We recently introduced a rat model of incubation of opioid craving after voluntary abstinence induced by negative consequences of drug seeking. Here, we used resting-state functional MRI to determine whether longitudinal functional connectivity changes in orbitofrontal cortex (OFC) circuits predict incubation of opioid craving after voluntary abstinence. We trained rats to self-administer for 14 d either intravenous oxycodone or palatable food. After 3 d, we introduced an electric barrier for 12 d that caused cessation of reward self-administration. We tested the rats for oxycodone or food seeking under extinction conditions immediately after self-administration training (early abstinence) and after electric barrier exposure (late abstinence). We imaged their brains before self-administration and during early and late abstinence. We analyzed changes in OFC functional connectivity induced by reward self-administration and electric barrier-induced abstinence. Oxycodone seeking was greater during late than early abstinence (incubation of oxycodone craving). Oxycodone self-administration experience increased OFC functional connectivity with dorsal striatum and related circuits that was positively correlated with incubated oxycodone seeking. In contrast, electric barrier-induced abstinence decreased OFC functional connectivity with dorsal striatum and related circuits that was negatively correlated with incubated oxycodone seeking. Food seeking was greater during early than late abstinence (abatement of food craving). Food self-administration experience and electric barrier-induced abstinence decreased or maintained functional connectivity in these circuits that were not correlated with abated food seeking. Opposing functional connectivity changes in OFC with dorsal striatum and related circuits induced by opioid self-administration versus voluntary abstinence predicted individual differences in incubation of opioid craving.

CRHCeA→VTA inputs inhibit the positive ensembles to induce negative effect of opiate withdrawal.

Plasticity of neurons in the ventral tegmental area (VTA) is critical for establishment of drug dependence. However, the remodeling of the circuits mediating the transition between positive and negative effect remains unclear. Here, we used neuronal activity-dependent labeling technique to characterize and temporarily control the VTA neuronal ensembles recruited by the initial morphine exposure (morphine-positive ensembles, Mor-Ens). Mor-Ens preferentially projected to NAc, and induced dopamine-dependent positive reinforcement. Electrophysiology and rabies viral tracing revealed the preferential connections between the VTA-projective corticotrophin-releasing hormone (CRH) neurons of central amygdala (CRHCeA→VTA) and Mor-Ens, which was enhanced after escalating morphine exposure and mediated the negative effect during opiate withdrawal. Pharmacologic intervention or CRISPR-mediated repression of CRHR1 in Mor-Ens weakened the inhibitory CRHCeA→VTA inputs, and alleviated the negative effect during opiate withdrawal. These data suggest that neurons encoding opioid reward experience are inhibited by enhanced CRHCeA→VTA inputs induced by chronic morphine exposure, leading to negative effect during opiate withdrawal, and provide new insight into the pathological changes in VTA plasticity after drug abuse and mechanism of opiate dependence.

Utility of a controlled amphetamine withdrawal paradigm among adults who use methamphetamine: A pilot clinical trial.

BACKGROUND: The continued increase in prevalence of methamphetamine use in the United States has resulted in a significant increase in the number of patients entering treatment for methamphetamine use. However, no robustly efficacious pharmacologic treatment for methamphetamine use or withdrawal has been identified to date after stopping methamphetamine use. AIMS: Given the association between methamphetamine withdrawal and relapse during early treatment, this study tested a controlled d-amphetamine withdrawal paradigm among methamphetamine-using individuals. METHODS: Treatment-seeking adults who used methamphetamine (N = 34; 47% female; 100% white) were enrolled in a 4-week, randomized, double-blind, placebo-controlled trial in a residential setting, in which all participants were maintained on d-amphetamine (30 mg BID) during week 1, then half were switched to placebo during weeks 2-3. All participants received placebo during week 4. Outcomes included vital signs, withdrawal, cravings for methamphetamine, mood, and cognition. Bivariate analyses tested treatment group differences on baseline demographic and outcome variables. Repeated measures models examined main and interaction effects of treatment over time. RESULTS/OUTCOMES: Participants were successfully randomized and safely stabilized on d-amphetamine. Craving for methamphetamine increased during weeks 2-3 in the placebo group relative to those on d-amphetamine. Interactions with age and heart rate were noted. CONCLUSIONS/INTERPRETATION: To our knowledge, this is the first double-blind, placebo-controlled trial measuring pharmacologic effects of abruptly stopping controlled d-amphetamine administration in adults who use methamphetamine. Results support the potential of this withdrawal paradigm to further examine the efficacy of pharmacologic agents in ameliorating methamphetamine withdrawal symptoms.

Gabapentinoid Pharmacology in the Context of Emerging Misuse Liability.

This article will review the epidemiology and pharmacology of gabapentinoids (gabapentin and pregabalin) relevant to their emerging misuse potential and provide guidance for clinical and regulatory management. Gabapentinoids are γ-aminobutyric acid analogues that produce their therapeutic effects by inhibiting voltage-gated calcium channels and decreasing neurotransmitter release. Recently gabapentinoid prescribing and use have increased tremendously. Although traditionally thought to possess a favorable safety profile, gabapentinoid misuse has also risen significantly. Gabapentinoid misuse generally occurs in combination with other substances, most notably opioids, and may be for purposes of eliciting euphoric effects, enhancing the effects of other substances, or self-treating conditions such as withdrawal, pain, anxiety, or insomnia. Given its faster onset, increased bioavailability and potency, and nonsaturable absorption, pregabalin's pharmacokinetics theoretically enhance its misuse liability versus gabapentin. However, gabapentin can produce similar euphoric effects, and epidemiologic studies have identified higher rates of gabapentin misuse in the United States, likely because of greater availability and less regulated prescribing. Although adverse events of gabapentinoid-only ingestion are relatively benign, a growing body of evidence indicates that gabapentinoids significantly increase opioid-related morbidity and mortality when used concomitantly. In addition, significant withdrawal effects may occur on abrupt discontinuation. As a result of these trends, several US states have begun to further regulate gabapentinoid prescribing, reclassifying it as a controlled substance or mandating reporting to local prescription drug-monitoring programs. Although increased regulation of gabapentin prescribing may be warranted, harm reduction efforts and increased patient and provider education are necessary to mitigate this concerning gabapentinoid misuse trend.

Sedative-Hypnotic Agents That Impact Gamma-Aminobutyric Acid Receptors: Focus on Flunitrazepam, Gamma-Hydroxybutyric Acid, Phenibut, and Selank.

There are many nonopioid central nervous system depressant substances that share a gamma-aminobutyric acid (GABA) receptor-related mechanism of action. These sedatives-hypnotics can be indicated to treat anxiety, seizures, depression, and insomnia but are also used as substances of abuse and used to facilitate sexual assault. Barbiturates, methaqualone, and glutethimide were among the first type A GABA receptor-mediated sedative-hypnotics. Their clinical use was limited for most indications by serious adverse events and strong abuse potential but continue to be used illicitly around the world. The benzodiazepines supplanted barbiturates for most indications because they were less likely to cause severe adverse events in monotherapy. Flunitrazepam is a newer benzodiazepine that is preferentially used recreationally and to facilitate sexual assault. Flunitrazepam has greater potency and higher affinity for the type A GABA receptor than most benzodiazepines. Gamma-hydroxybutyric acid is sought illicitly for its hypnotic, euphoric and anabolic effects as well as to facilitate sexual assault. When any of these GABAergic drugs are used in high doses or with other sedative hypnotic agents, respiratory depression, coma, and death have occurred. Chronic use of these GABAergic drugs can lead to significant withdrawal syndromes. Phenibut and selank are poorly studied Russian drugs with GABAergic mechanisms that are inexplicably sold to US consumers as dietary supplements. Poison control center calls regarding phenibut have increased substantially over the past 5 years. Desired euphoriant effects account for the recreational and illicit use of many GABA-modulating agents. However, illicit use can lead to significant toxicities related to abuse, dependence, and subsequent withdrawal syndromes. Significant evaluation of developing agents with GABA properties should be conducted to determine abuse potential before public access ensues.

Circadian rhythm influences naloxone induced morphine withdrawal and neuronal activity of lateral paragigantocellularis nucleus.

Investigations have shown that the circadian rhythm can affect the mechanisms associated with drug dependence. In this regard, we sought to assess the negative consequence of morphine withdrawal syndrome on conditioned place aversion (CPA) and lateral paragigantocellularis (LPGi) neuronal activity in morphine-dependent rats during light (8:00-12:00) and dark (20:00-24:00) cycles. Male Wistar rats (250-300 g) were received 10 mg/kg morphine or its vehicle (Saline, 2 mL/kg/12 h, s.c.) in 13 consecutive days for behavioral assessment tests. Then, naloxone-induced conditioned place aversion and physical signs of withdrawal syndrome were evaluated during light and dark cycles. In contrast to the behavioral part, we performed in vivo extracellular single-unit recording for investigating the neural response of LPGi to naloxone in morphine-dependent rats on day 10 of morphine/saline exposure. Results showed that naloxone induced conditioned place aversion in both light and dark cycles, but the CPA score during the light cycle was larger. Moreover, the intensity of physical signs of morphine withdrawal syndrome was more severe during the light cycle (rest phase) compare to the dark one. In electrophysiological experiments, results indicated that naloxone evoked both excitatory and inhibitory responses in LPGi neurons and the incremental effect of naloxone on LPGi activity was stronger in the light cycle. Also, the neurons with the excitatory response exhibited higher baseline activity in the dark cycle, but the neurons with the inhibitory response showed higher baseline activity in the light cycle. Interestingly, the baseline firing rate of neurons recorded in the light cycle was significantly different in response (excitatory/inhibitory) -dependent manner. We concluded that naloxone-induced changes in LPGi cellular activity and behaviors of morphine-dependent rats can be affected by circadian rhythm and the internal clock.

Psychedelic drug use and schizotypy in young adults.

Despite recently resurrected scientific interest in classical psychedelics, few studies have focused on potential harms associated with abuse of these substances. In particular, the link between psychedelic use and psychotic symptoms has been debated while no conclusive evidence has been presented. Here, we studied an adult population (n = 1032) with a special focus on young (18-35 years) and healthy individuals (n = 701) to evaluate the association of psychedelic drug use with schizotypy and evidence integration impairment typically observed in psychosis-spectrum disorders. Experimental behavioural testing was performed in a subsample of the subjects (n = 39). We observed higher schizotypy scores in psychedelic users in the total sample. However, the effect size was notably small and only marginally significant when considering young and healthy subjects (Cohen's d = 0.13). Controlling for concomitant drug use, none of our analyses found significant associations between psychedelic use and schizotypal traits. Results from experimental testing showed that total exposure to psychedelics (frequency and temporal proximity of use) was associated with better evidence integration (Cohen's d = 0.13) and a higher sensitivity of fear responses (Cohen's d = 1.05) to the effects instructed knowledge in a reversal aversive learning task modelled computationally with skin conductance response and pupillometry. This effect was present even when controlling for demographics and concomitant drug use. On a group level, however, only difference in sensitivity of fear responses to instructed knowledge reached statistical significance. Taken together, our findings suggest that psychedelic drug use is only weakly associated with psychosis-like symptoms, which, in turn, is to a large extent explained by psychiatric comorbidities and use of other psychoactive substances. Our results also suggest that psychedelics may have an effect on flexibility of evidence integration and aversive learning processes, that may be linked to recently suggested therapeutic effects of psychedelic drugs in non-psychotic psychiatric populations.

Perivascular cell-derived extracellular vesicles stimulate colorectal cancer revascularization after withdrawal of antiangiogenic drugs.

Antiangiogenic tyrosine kinase inhibitors (AA-TKIs) have become a promising therapeutic strategy for colorectal cancer (CRC). In clinical practice, a significant proportion of cancer patients temporarily discontinue AA-TKI treatment due to recurrent toxicities, economic burden or acquired resistance. However, AA-TKI therapy withdrawal-induced tumour revascularization frequently occurs, hampering the clinical application of AA-TKIs. Here, this study demonstrates that tumour perivascular cells mediate tumour revascularization after withdrawal of AA-TKI therapy. Pharmacological inhibition and genetic ablation of perivascular cells largely attenuate the rebound effect of CRC vascularization in the AA-TKI cessation experimental settings. Mechanistically, tumour perivascular cell-derived extracellular vehicles (TPC-EVs) contain Gas6 that instigates the recruitment of endothelial progenitor cells (EPCs) for tumour revascularization via activating the Axl pathway. Gas6 silence and an Axl inhibitor markedly inhibit tumour revascularization by impairing EPC recruitment. Consequently, combination therapy of regorafenib with the Axl inhibitor improves overall survival in mice metastatic CRC model by inhibiting tumour growth. Together, these data shed new mechanistic insights into perivascular cells in off-AA-TKI-induced tumour revascularization and indicate that blocking the Axl signalling may provide an attractive anticancer approach for sustaining long-lasting angiostatic effects to improve the therapeutic outcomes of antiangiogenic drugs in CRC.