Cognitive and socio-cognitive functioning of chronic non-medical prescription opioid users

Substance Use-Related Alterations of Social Decision Making in a Longitudinal Cohort of Young Adults

BACKGROUND

Substance use disorders are associated with severe negative social and health-related outcomes. Evidence has accumulated that long-term substance use is associated with alterations in social interaction behavior, which likely contributes to the vicious cycle of substance use disorder. However, little is known about whether these social problems originate from contextual factors only or also from the substance use itself-in other words, if they are predisposed or substance induced.

METHODS

We studied the causation behind behavioral alterations of substance users over a 9-year period (ages 11-20 years) in an urban age cohort (N = 1002) with a high prevalence of substance use at age 20. We identified common substance use patterns using toxicological hair analysis, examined behavioral alterations with incentivized games, and used teacher assessments across different ages to determine the causes and effects that underlie substance use-related impairments in social interaction.

RESULTS

We found that opioid and stimulant users showed reduced prosocial behavior compared with nonusers, particularly in interpersonal trust and perspective taking (e.g., they were approximately 50% less likely to trust others). Our longitudinal analyses suggest a causal relationship between the nonmedical use of prescription opioids and impaired social behavior, whereas impairments among stimulant users seem to be partially predisposed. Moreover, women tended to be more severely affected by opioid use than men. However, no behavioral alterations were found among young adult cannabis or ecstasy users.

CONCLUSIONS

Highly addictive substances such as opioids can impair users' social behavior by undermining fundamental human interaction, thereby fueling a vicious cycle of substance use and social isolation.

Endocannabinoids and related lipids linked to social exclusion in individuals with chronic non-medical prescription opioid use

Opioid-related overdose deaths are still on the rise in North America, emphasizing the need to better understand the underlying neurobiological mechanisms regarding the development of opioid use disorder (OUD). Recent evidence from preclinical and clinical studies indicate that the endocannabinoid system (ECS) may play a crucial role in stress and reward, both involved in the development and maintenance of substance use disorders. Animal models demonstrate a specific crosstalk between the ECS and the endogenous opioid system. However, translational studies in humans are scarce. Here, we investigated basal plasma levels of the endocannabinoids anandamide (AEA) and 2-arachidonoyglycerol (2-AG), and eight endocannabinoid-related lipids, including oleoylethanolamide (OEA) and palmitoylethanolamide (PEA), as well as whole blood fatty acid amide hydrolase (FAAH) activity in chronic non-medical prescription opioid users (NMPOU; n = 21) compared to opioid-naïve healthy controls (n = 29) considering age, sex, and cannabis use as potential confounders. Additionally, the association of endocannabinoids and related lipids with the participants' response to experimentally induced social exclusion was examined. We found significantly elevated basal AEA, OEA, and PEA levels in NMPOU compared to controls, but no differences in FAAH activity, 2-AG, or other endocannabinoid-related lipids. Within NMPOU, higher AEA levels were associated with lower perception of social exclusion. Robust positive correlations within N-acylethanolamines (i.e., AEA, OEA, and PEA) indicate strong metabolic associations. Together with our recent findings of elevated basal 2-AG levels in dependent cocaine users, present results indicate substance-specific alterations of the ECS that may have implications in the search for novel therapeutic interventions for these populations.

Dissecting shared pain representations to understand their behavioral and clinical relevance

Accounts of shared representations posit that the experience of pain and pain empathy rely on similar neural mechanisms. Experimental research employing novel analytical and methodological approaches has made significant advances in both the identification and targeted manipulation of such shared experiences and their neural underpinnings. This revealed that painful experiences can be shared on different representational levels, from pain-specific to domain-general features, such as negative affect and its regulation. In view of direct links between such representations and social behaviors such as prosocial behavior, conditions characterized by aberrant pain processing may come along with heavy impairments in the social domain, depending on the affected representational level. This has wide potential implications in light of the high prevalence of pain-related clinical conditions, their management, and the overuse of pain medication. In this review and opinion paper, we aim to chart the path toward a better understanding of the link between shared affect and prosocial behavior.

Persistent effects of repeated adolescent and adult heroin vapor inhalation in female Wistar rats

Adolescent drug exposure has been associated with more severe mental health outcomes related to substance abuse and anxiety disorders. The aim of the present study was to contrast the long-term effects of repeated heroin vapor inhalation during adolescence with similar heroin exposure in adulthood. Groups of female Wistar rats underwent twice daily 30-minute sessions of heroin or propylene glycol (control) vapor inhalation from postnatal days (PND) 36-45 or PND 85-94, respectively. Nociception was assessed after vapor inhalation sessions and forty days later, for the Adolescent-Exposed and Adult-Exposed groups. Anxiety-like behavior was assessed with an elevated plus-maze (EPM) and spatial learning was assessed with a Barnes maze. Acute effects of naloxone (0.3 mg/kg, i.p.) and heroin (0.5 and 1.0 mg/kg, s.c.) on thermal nociception were determined on PND 140/189 and PND 149/198, respectively. Repeated heroin vapor inhalation produced anti-nociceptive tolerance across sessions in both adolescent and adult rats, with the adolescents exhibiting more complete tolerance. Heroin vapor inhalation produced anxiolytic effects, regardless of age of exposure. There were no effects of heroin on spatial learning. Naloxone produced acute hyperalgesia in all but the Adolescent-Exposed heroin group, and heroin anti-nociception was blunted in both heroin-exposed groups at the highest heroin dose. Repeated heroin vapor inhalation can produce lasting effects on nociception and anxiety-like behavior that persist for months after the exposure. Importantly, these findings suggest that adolescent exposure to heroin vapor produces specific effects on nociception that are not observed when exposure occurs in adulthood.

Associations of psychoactive substances and steroid hormones in hair: Findings relevant to stress research from a large cohort of young adults

OBJECTIVE

Epidemiological studies increasingly use hair samples to assess people's cumulative exposure to steroid hormones, but how the use of different psychoactive substances may affect steroid hormone levels in hair is, so far, largely unknown. The current study addresses this gap by establishing the substance exposure correlates of cortisol, cortisone, and testosterone in hair, while also accounting for a number of relevant covariates.

METHOD

Data came from a large urban community-sample of young adults with a high prevalence of substance use (N = 1002, mean age=20.6 years, 50.2% female), who provided 3 cm of hair samples. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) quantified cortisol, cortisone, and testosterone, as well as delta-9-tetrahydrocannabinol (THC), 3,4-methylenedioxymethamphetamine (MDMA, "Ecstasy"), cocaine, several opioids, and their respective metabolites. Multiple linear regression models with covariates were used to predict steroid hormone levels from substance exposure in a four-step approach: In the full sample, low and high substance hair concentrations (median split) were first tested against no use for each substance individually (step 1) and for all substances together (step 2). Then, within the participants with any substance in hair only, the continuous hair concentration of each substance in pg/mg (step 3) and finally of all substances together, were regressed (step 4).

RESULTS

Low, high, and continuous levels of THC in hair were robustly associated with higher levels of cortisol (sig. in step 1 low THC: β = 0.29, p = .021; high THC: β = 0.42, p = .001; step 2: low THC: β = 0.27, p = 0.036, and high THC: β = 0.40, p = .004, and step 4: β = 0.12, p = .041). Participants with high MDMA levels had higher levels of cortisone without adjusting for other substances (step 1: β = 0.34, p = .026), but this effect was not significant in the other models. While high THC levels were associated with lower levels of testosterone in step 2 (β = -0.35, p = .018), MDMA concentration was positively related to testosterone concentration with and without adjusting for other substances (step 3: β = 0.24, p = .041; step 4: β = 0.17, 95%, p = .015) in male participants.

CONCLUSION

The use of psychoactive substances, especially of cannabis and ecstasy, should be considered in studies investigating steroid hormones in hair.

The intersection of empathy and addiction

Empathy, the ability to perceive the affective state of another, is a complex process that is integral to many of the prosocial behaviors expressed in humans and across the animal kingdom. Research into the behavioral and neurobiological underpinnings of empathic behaviors has increased in recent years. Growing evidence suggests changes in empathy may contribute to a myriad of psychiatric illnesses, including substance use disorder (SUD). Indeed, both clinical and preclinical research in SUD demonstrates a strong relationship between drug taking or relapse events and changes to empathic behavior. Further, there is significant overlap in the underlying neural substrates of these complex behaviors, including the insula, paraventricular nucleus of thalamus (PVT), and the paraventricular nucleus of the hypothalamus (PVN). In this review, we will discuss our current understanding of the interplay between empathic behaviors and SUD. We will also examine the underlying neurobiology that may regulate this interaction, focusing specifically on the insula, PVT, and PVN. Finally, we discuss the biologic and therapeutic importance of taking empathic processes into consideration when discussing SUD.

Tau protein plays a role in the mechanism of cognitive disorders induced by anesthetic drugs

Cognitive disorders are mental health disorders that can affect cognitive ability. Surgery and anesthesia have been proposed to increase the incidence of cognitive dysfunction, including declines in memory, learning, attention and executive function. Tau protein is a microtubule-associated protein located in the axons of neurons and is important for microtubule assembly and stability; its biological function is mainly regulated by phosphorylation. Phosphorylated tau protein has been associated with cognitive dysfunction mediated by disrupting the stability of the microtubule structure. There is an increasing consensus that anesthetic drugs can cause cognitive impairment. Herein, we reviewed the latest literature and compared the relationship between tau protein and cognitive impairment caused by different anesthetics. Our results substantiated that tau protein phosphorylation is essential in cognitive dysfunction caused by anesthetic drugs, and the possible mechanism can be summarized as "anesthetic drugs-kinase/phosphatase-p-Tau-cognitive impairment".

Effects of the mu-opioid receptor agonist morphine on facial mimicry and emotion recognition

Facial mimicry and emotion recognition are two socio-cognitive abilities involved in adaptive socio-emotional behavior, promoting affiliation and the establishment of social bonds. The mu-opioid receptor (MOR) system plays a key role in affiliation and social bonding. However, it remains unclear whether MORs are involved in the categorization and spontaneous mimicry of emotional facial expressions. Using a randomized, placebo-controlled, double-blind, between-subjects design, we investigated in 82 healthy female volunteers the effects of the specific MOR agonist morphine on the recognition accuracy of emotional faces (happiness, anger, fear), and on their facial mimicry (measured with electromyography). Frequentist statistics did not reveal any significant effects of drug administration on facial mimicry or emotion recognition abilities. However, post hoc Bayesian analyses provided support for an effect of morphine on facial mimicry of fearful facial expressions. Specifically, compared to placebo, morphine reduced mimicry of fear, as shown by lower activity of the frontalis muscle. Bayesian analyses also provided support for the absence of a drug effect on mimicry of happy and angry facial expressions, which were assessed with the zygomaticus major and corrugator supercilii muscles, as well as on emotion recognition accuracy. These findings suggest that MOR activity is involved in automatic facial responses to fearful stimuli, but not in their identification. Overall, the current results, together with the previously reported small effects of opioid compounds, suggest a relatively marginal role of the MOR system in emotion simulation and perception.

Modafinil rescues repeated morphine-induced synaptic and behavioural impairments via activation of D1R-ERK-CREB pathway in medial prefrontal cortex

Long-term opioid abuse causes a variety of long-lasting cognitive impairments such as attention, impulsivity and working memory. These cognitive impairments undermine behavioural treatment for drug abuse and lead to poor treatment retention and outcomes. Modafinil is a wake-promoting drug that shows potential in improving attention and memory in humans and animals. However, modafinil's effect on opioid-induced cognitive impairments remains unclear, and the underlying mechanism is poorly understood. This study showed that repeated morphine administration significantly impairs attention, increases impulsivity and reduces motivation to natural rewards in mice. Systemic modafinil treatment at low dose efficiently ameliorates morphine-induced attention dysfunction and improves motivation and working memory in mice. High dose of modafinil has adverse effects on impulsive action and attention. Local infusion of D1R antagonist SCH-23390 reverses the morphine-induced synaptic abnormalities and activation of the D1R-ERK-CREB pathway in medial prefrontal cortex (mPFC). This study demonstrated a protective effect of modafinil in mPFC neurons and offered a therapeutic potential for cognitive deficits in opioid abuse.

Neurocognitive impairments and brain abnormalities resulting from opioid-related overdoses: A systematic review

BACKGROUND

Non-fatal opioid-related overdoses have increased significantly over the past two decades and there have been increasing reports of brain injuries and/or neurocognitive impairments following overdose events. Limited preclinical research suggests that opioid overdoses may cause brain injury; however, little is known about such injuries in humans. The purpose this systematic review is to summarize existing studies on neurocognitive impairments and/or brain abnormalities associated with an opioid-related overdose in humans.

METHODS

PubMed, Web of Science, Ovid MEDLINE and PsyINFO were searched, without year restrictions, and identified 3099 articles. An additional 24 articles were identified by reviewing references. Articles were included if they were published in English, reported study findings in humans, included individuals 18 years of age or older, and reported an objective measure of neurocognitive impairments and/or brain abnormalities resulting from an opioid-related overdose. Six domains of bias (selection, performance, attrition, detection (two dimensions) and reporting were evaluated and themes were summarized.

RESULTS

Seventy-nine journal articles, published between 1973-2020, were included in the review. More than half of the articles were case reports (n = 44) and there were 11 cohort studies, 18 case series, and 6 case-control studies. All of the studies were categorized as at-risk of bias, few controlled for confounding factors, and methodological differences made direct comparisons difficult. Less than half of the studies reported toxicology results confirming an opioid-related overdose; 64.6 % reported brain MRI results and 27.8 % reported results of neuropsychological testing. Only two studies had within subject comparative data to document changes in the brain possibly associated with an overdose. Despite these limitations, existing publications suggest that brain injuries and neurocognitive impairments are associated with opioid overdose. Additional research is needed to establish the incidence of overdose-related brain injuries and the potential impact on functioning, as well as engagement in treatment of substance use disorders.

CONCLUSIONS

Respiratory depression is a defining characteristic of opioid overdose and prolonged cerebral hypoxia may cause brain injuries and/or neurocognitive impairments. The onset, characteristics, and duration of such injuries is variable and additional research is needed to understand their clinical implications.

A Comprehensive Multi-Analyte Method for Hair Analysis: Substance-Specific Quantification Ranges and Tool for Task-Oriented Data Evaluation

The aim of the present study was to quantify a large number of analytes including opioids, stimulants, benzodiazepines, z-drugs, antidepressants and neuroleptics within a single sample workup followed by a single analytical measurement. Expected drug concentrations in hair are strongly substance dependent. Therefore, three different calibration ranges were implemented: 0.5 to 600 pg/mg (group 1), 10 to 12,000 pg/mg (group 2) and 50 to 60,000 pg/mg (group 3). In order to avoid saturation effects, different strategies were applied for selected transitions including the use of parent mass ions containing one or two 13C-isotopes and detuning of the declustering potential and/or collision energy. Drugs were extracted from pulverized hair by a two-step extraction protocol and measured by liquid chromatrography--tandem mass spectrometry (LC--MS-MS) using Scheduled MRM™ Algorithm Pro. In total, 275 MRM transitions including 43 deuterated standards were measured. The method has been fully validated according to international guidelines. A MultiQuant™ software based tool for task-oriented data evaluation was established, which allows extracting selected information from the measured data sets. The matrix effects and recoveries were within the allowed ranges for the majority of the analytes. The lower limits of quantification (LLOQs) were for ∼72% of the analytes in the low-pg/mg range (0.5-5 pg/mg) and for ∼24% of the analytes between 10 and 50 pg/mg. These LLOQs considered cut-offs by the Society of Hair Testing (SoHT), if recommended. The herein established multi-analyte approach meets the specific requirements of forensic hair testing and can be used for the rapid and robust measurement of a wide range of psychoactive substances. The analyte-specific wide concentration ranges open up a wide field of applications.

Insights into the Decontamination of Cocaine-Positive Hair Samples

A highly discussed step in hair sample preparation for forensic analytics is the applied decontamination. The here presented investigations aim to gain insight and give recommendations on how to conduct this decontamination for the analysis of cocaine consumption in hair. Key insights were gained from the investigation of cocaine consumer hair, which was artificially contaminated in a humid atmosphere with ¹³C₆ labelled cocaine and from cocaine powder contaminated hair. Several decontamination protocols were investigated, whereby the usage of a decontamination protocol consisting of multiple short repetitive washes allowed to visualize the wash out of (¹³C₆-) cocaine. Multiple methanol washes proved to be an efficient and simple decontamination approach. Our findings showed that decontamination protocols can successfully wash out recent cocaine contaminations. They were observed to be rather quickly washed out, whereas cocaine from consumption or “older” cocaine contaminations were shown to eliminate both at a constant rate (from inner hair compartments). Thus, the usage of decontamination protocols to differentiate between consumption and contamination was shown to be limited. As contamination can happen any time at any level, only the application of elaborated decision trees, based on cocaine metabolite ratios and thresholds, can provide the distinction between consumption and contamination. Thus, the authors highly recommend the usage of such tools on all hair samples analyzed for cocaine consumption.

A vicious cycle of neuropathological, cognitive and behavioural sequelae of repeated opioid overdose

In the midst of an escalating U.S. opioid crisis, the immediate focus of public health interventions is on fatal overdose prevention. Few studies, however, have sought to examine the long-term health consequences of exposure to repeated nonfatal opioid overdose. We reviewed recent literature to examine three corresponding downstream health outcomes of repeated overdose: a) neurodegenerative processes; b) cognition and memory; and c) overdose risk behaviours. We found a remarkable congruency among available biochemical and cognitive data on how nonfatal overdose precipitates various pathological feedforward and feedback loops that affect people who use opioids for years to come. We found however that downstream behavioural implications of neurodegenerative and cognitive sequelae are less studied despite being most proximal to an overdose. Findings point to a vicious cycle of nonfatal overdose leading to neurodegeneration - closely resembling Alzheimer Disease - that results in cognitive decline that in turn leads to potentially reduced adherence to safe drug use behaviours. The collected evidence not only brings into the focus the long-term health consequences of nonfatal overdose from the perspectives of biology, neuroscience, and public health, but also creates new cross-disciplinary context and awareness in the research and public health community that should benefit people at risk.

Neuronal apoptosis induced by morphine withdrawal is mediated by the p75 neurotrophin receptor

Morphine withdrawal evokes neuronal apoptosis through mechanisms that are still under investigation. We have previously shown that morphine withdrawal increases the levels of pro-brain-derived neurotrophic factor (BDNF), a proneurotrophin that promotes neuronal apoptosis through the binding and activation of the pan-neurotrophin receptor p75 (p75NTR). In this work, we sought to examine whether morphine withdrawal increases p75NTR-driven signaling events. We employed a repeated morphine treatment-withdrawal paradigm in order to investigate biochemical and histological indicators of p75NTR-mediated neuronal apoptosis in mice. We found that repeated cycles of spontaneous morphine withdrawal promote an accumulation of p75NTR in hippocampal synapses. At the same time, TrkB, the receptor that is crucial for BDNF-mediated synaptic plasticity in the hippocampus, was decreased, suggesting that withdrawal alters the neurotrophin receptor environment to favor synaptic remodeling and apoptosis. Indeed, we observed evidence of neuronal apoptosis in the hippocampus, including activation of c-Jun N-terminal kinase (JNK) and increased active caspase-3. These effects were not seen in saline or morphine-treated mice which had not undergone withdrawal. To determine whether p75NTR was necessary in promoting these outcomes, we repeated these experiments in p75NTR heterozygous mice. The lack of one p75NTR allele was sufficient to prevent the increases in phosphorylated JNK and active caspase-3. Our results suggest that p75NTR participates in the neurotoxic and proinflammatory state evoked by morphine withdrawal. Because p75NTR activation negatively influences synaptic repair and promotes cell death, preventing opioid withdrawal is crucial for reducing neurotoxic mechanisms accompanying opioid use disorders.

Social Information Processing in Substance Use Disorders: Insights From an Emotional Go-Nogo Task

Positive social connections are crucial for recovery from Substance Use Disorder (SUD). Of interest is understanding potential social information processing (SIP) mediators of this effect. To explore whether persons with different SUD show idiosyncratic biases toward social signals, we administered an emotional go-nogo task (EGNG) to 31 individuals with Cocaine Use Disorder (CoUD), 31 with Cannabis Use Disorder (CaUD), 79 with Opioid Use Disorder (OUD), and 58 controls. Participants were instructed to respond to emotional faces (Fear/Happy) but withhold responses to expressionless faces in two task blocks, with the reverse instruction in the other two blocks. Emotional faces as non-targets elicited more "false alarm" (FA) commission errors as a main effect. Groups did not differ in overall rates of hits (correct responses to target faces), but participants with CaUD and CoUD showed reduced rates of hits (relative to controls) when expressionless faces were targets. OUD participants had worse hit rates [and slower reaction times (RT)] when fearful faces (but not happy faces) were targets. CaUD participants were most affected by instruction effects (respond/"go" vs withhold response/"no-go" to emotional face) on discriminability statistic A. Participants were faster to respond to happy face targets than to expressionless faces. However, this pattern was reversed in fearful face blocks in OUD and CoUD participants. This experiment replicated previous findings of the greater salience of expressive face images, and extends this finding to SUD, where persons with CaUD may show even greater bias toward emotional faces. Conversely, OUD participants showed idiosyncratic behavior in response to fearful faces suggestive of increased attentional disruption by fear. These data suggest a mechanism by which positive social signals may contribute to recovery.

Treating Opioid Use Disorder in Peripartum Mothers: A Look at the Psychodynamics, Neurobiology, and Potential Role of Oxytocin

The peripartum period (pregnancy and postpartum) is a unique time filled with psychodynamic and biological changes that are critical in affecting the lives of mother and baby. Attachment, the biologically based emotional connection between a caregiver and infant, is critical to the development of the child. The early interactions in an infant's life shape their reward neuro-circuitry and the development of their internal working models and styles of attachment. Opioid use disorders in the mother affect the psychodynamics and neurobiology of attachment. There is significant overlap between the neurobiology of attachment and that of opioid use disorders. In this article, we hope to describe how opioid use disorders affect mother-infant attachment and how psychodynamic psychotherapy that is informed by attachment theory may be a potential treatment for mothers with opioid use disorders. Further, oxytocin plays a role in the attachment process and may function abnormally in mothers with opioid use disorders. As oxytocin affects attachment, administration of oxytocin during postpartum mother-infant interactions in the setting of psychotherapy may facilitate bonding and promote recovery from opioid use disorders in the peripartum population.

Chronic Exposure to Morphine Leads to a Reduced Affective Pain Response in the Presence of Hyperalgesia in an Animal Model of Empathy

Background

Empathy is the capability to represent the mental and emotional states of other subjects. Previous studies have demonstrated a possible correlation between morphine addiction and altered empathy response in morphine-addicted subjects. This study was performed to evaluate the effect of chronic morphine exposure as an animal model of morphine addiction on empathic changes in affective and sensory pain.

Methods

Adult male Wistar rats (3 months old) were used for the current study. Animals were grouped in cages of two (n = 8 for each group) and one animal was selected as the pain observer group. Pain observer animals received either saline or morphine (10 mg/kg, twice daily for 8 days). At ninth day, formalin [50 µg, 5%, subcutaneous (SC)] was injected into the hindpaw of the cagemate and placed inside the cage. Elevated plus maze (EPM) and open field test (OFT) were recruited to evaluate anxiety; hot plate and tail flick tests were used to assay sensory pain. Conditioned place aversion (CPA) was also measured as indicator of affective pain component.

Findings

Chronic morphine exposure led to a reduced level of anxiety in EPM and OFT assays. An opioid-induced hyperalgesia was observed in the sensory pain assays, while there was a reduced affective pain in the CPA paradigm in morphine-treated animals.

Conclusion

It might be plausible that chronic morphine exposure might alter empathy for pain through affective and not sensory pain pathways.

Chronic non-medical prescription opioid use and empathy for pain: Does pain make the difference?

Non-medical prescription opioid use (NMPOU) is at the heart of the opioid epidemic in the United States. Although chronic opioid use is commonly accompanied by deficits in social functioning, little is known about the impact of chronic NMPOU on social cognitive functions. Social neuroscience models suggest that empathy activates similar or even equivalent neural structures as those underpinning the first-hand experience in that emotional state (e.g., pain). Therefore, we measured subjective and psychophysiological responses during an empathy-for-pain task in 23 individuals with NMPOU, objectively confirmed by hair and urine testing, and compared them with 29 opioid-naïve healthy controls. NMPOU individuals showed lower other-related and self-related unpleasantness ratings when seeing others in pain than controls. No differences between the control and NMPOU group were found in skin conductance responses and heart rate variability (HRV) assessed by root mean square of successive differences (RMSSD) in response to the task. However, RMSSD-HRV was strongly negatively correlated with self-related unpleasantness and craving in the NMPOU group. A subsequent mediation analysis showed a total effect of RMSSD-HRV on self-related unpleasantness with no mediation of craving. This indicates that stronger emotion regulation indexed by high RMSSD-HRV might have downregulating effects on sharing others' pain in NMPOU individuals but not in healthy controls, which was further accompanied by decreased ratings of personal distress and empathetic concern. These results contribute to a better understanding of social functioning in chronic opioid users, suggesting adequate emotion regulation and empathy trainings as therapeutic targets for future interventions of opioid use disorders and long-term pain treatment with opioids.

Prolonged Withdrawal From Escalated Oxycodone Is Associated With Increased Expression of Glutamate Receptors in the Rat Hippocampus

People suffering from opioid use disorder (OUD) exhibit cognitive dysfunctions. Here, we investigated potential changes in the expression of glutamate receptors in rat hippocampi at 2 h and 31 days after the last session of oxycodone self-administration (SA). RNA extracted from the hippocampus was used in quantitative polymerase chain reaction analyses. Rats, given long-access (9 h per day) to oxycodone (LgA), took significantly more drug than rats exposed to short-access (3 h per day) (ShA). In addition, LgA rats could be further divided into higher oxycodone taking (LgA-H) or lower oxycodone taking (LgA-L) groups, based on a cut-off of 50 infusions per day. LgA rats, but not ShA, rats exhibited incubation of oxycodone craving. In addition, LgA rats showed increased mRNA expression of GluA1-3 and GluN2a-c subunits as well as Grm3, Grm5, Grm6, and Grm8 subtypes of glutamate receptors after 31 days but not after 2 h of stopping the SA experiment. Changes in GluA1-3, Grm6, and Grm8 mRNA levels also correlated with increased lever pressing (incubation) after long periods of withdrawal from oxycodone. More studies are needed to elucidate the molecular mechanisms involved in altering the expression of these receptors during withdrawal from oxycodone and/or incubation of drug seeking.

Dual-specificity phosphatase 15 (DUSP15) in the nucleus accumbens is a novel negative regulator of morphine-associated contextual memory

Drug relapse among addicts often occurs due to the learned association between drug-paired cues and the rewarding effects of these drugs, such as morphine. Contextual memory associated with morphine has a central role in maintenance and relapse. We showed that morphine-conditioned place preference (CPP) activates extracellular-regulated protein kinase (ERK) in the nucleus accumbens (NAc). The main enzymes that mediate ERK dephosphorylation are members of the dual-specificity phosphatase (DUSP) superfamily. It is unclear which members regulate the morphine CPP-induced activation of ERK. After screening, DUSP15 was found to be decreased during both morphine CPP expression and the reinstatement period. Intra-NAc infusions of AAV-DUSP15 (overexpression) not only prevented the expression of morphine-induced CPP but also facilitated extinction, inhibited reinstatement, and abolished ERK activation. However, after repeated morphine exposure and withdrawal in mice, there was no change in the expression of p-ERK and DUSP15, and the overexpression of DUSP15 in the NAc did not improve the impaired spatial memory or anxiety-like behaviour induced by morphine. Together, these findings indicate that DUSP15 not only prevents the expression of drug-paired contextual memory but also promotes the extinction of existing addiction memories, thus providing a novel therapeutic target for the treatment of drug addiction.

When Physical and Social Pain Coexist: Insights Into Opioid Therapy

The US opioid epidemic challenges us to rethink our understanding of the function of opioids and the nature of chronic pain. We have neatly separated opioid use and abuse as well as physical and social pain in ways that may not be consistent with the most recent neuroscientific and epidemiological research. Physical injury and social rejection activate similar brain centers. Many of the patients who use opioid medications long term for the treatment of chronic pain have both physical and social pain, but these medications may produce a state of persistent opioid dependence that suppresses the endogenous opioid system that is essential for human socialization and reward processing. Recognition of the social aspects of chronic pain and opioid action can improve our treatment of chronic pain and our use of opioid medications.

Restoration of prosocial behavior in rats after heroin self-administration via chemogenetic activation of the anterior insular cortex

The anterior insular cortex (AIC) mediates various social, emotional, and interoceptive components of addiction. We recently demonstrated a disruption of prosocial behavior following heroin self-administration in rats, as assessed by examining the animals' propensity to rescue its cagemate from a plastic restrainer while having simultaneous access to heroin. To examine the possibility that heroin-induced deficits in prosocial function are mediated by the AIC, the present study examined the effects of chemogenetic activation or inhibition of excitatory AIC pyramidal neurons on heroin-induced prosocial deficits. After establishment of baseline rescuing behavior, rats received bilateral infusions of viral vectors encoding either a control virus (AAV-CaMKIIα-GFP), stimulatory DREADD (AAV-CaMKIIα-hM3Dq-mCherry) (Experiment 1), or inhibitory DREADD (AAV-CaMKIIα-hM4Di-mCherry) (Experiment 2), into the AIC. Rats were then allowed to self-administer heroin (0.06 mg/kg/infusion) 6 hr/day for 2 weeks. Prior to re-assessment of prosocial behavior, animals were administered clozapine-N-oxide (1.5 mg/kg, i.p.) to assess the effects of chemogenetic activation or inhibition of the AIC. Relative to control animals, chemogenetic activation of the AIC reversed deficits in rescuing behavior induced by heroin, whereas chemogenetic inhibition of the AIC had no effect. We hypothesize that stimulatory neuromodulation of the AIC may be a novel approach for restoring prosociality in opiate abuse.

Social and Non-Social Cognitive Enhancement in Cocaine Users-A Closer Look on Enhancement Motives for Cocaine Consumption

BACKGROUND

Cognitive disturbances of chronic cocaine users (CU) have been repeatedly investigated. However, it is yet unknown how CU using cocaine for cognitive or social enhancement differ from stimulant-naïve controls and CU that do not have these motives. More precisely, we assumed that CU with an enhancement motive self-medicate deficits in specific cognitive abilities, i.e., they use cocaine to enhance their performance in either social (social motive) or non-social cognitive situations (cognitive motive).

METHODS

Forty-two CU were categorized according to their motives for cocaine consumption into social and non-social motive groups as well as cognitive and non-cognitive motive groups, respectively. Subsequently, CU motive groups were compared to 48 stimulant-naïve controls in their social and non-social cognitive functioning applying a comprehensive neuropsychological test battery.

RESULTS

The social motive group showed deficits in cognitive empathy compared to controls (Cohen's d = 0.65) and the non-social motive group (d = 0.60). No mentionable effects were found for emotional empathy and Theory-of-Mind. Cognitive and non-cognitive motive groups both showed general cognitive deficits but with different patterns of impairments compared to controls: the cognitive motive group had deficits mainly in working memory (d = 0.84) and declarative memory (d = 0.60), whereas the non-cognitive motive group also had deficits in working memory (d = 0.61) but additionally in executive functions (d = 0.67). For the domains declarative memory and executive functions, the respective other CU group displayed intermediate performance.

CONCLUSIONS

This study demonstrates that cocaine is partially instrumentalized by CU with specific enhancement motives to counteract related cognitive impairments.

Impaired empathy and increased anger following social exclusion in non-intoxicated opioid users

RATIONALE

Social functioning is modulated by the endogenous opioid system. In opioid use disorder, social functioning appears disrupted, but little research has delineated the nature of these deficits and their relationship to acute opioid use.

OBJECTIVES

The current study aimed to assess both emotional and cognitive empathy, along with subjective and physiological responses to social exclusion in opioid users who were either acutely intoxicated or non-intoxicated from using opioids.

METHODS

Individuals on an opioid substitution medication (OSM) were divided into 'intoxicated users' (had taken their OSM the same day as testing, n = 20) and 'non-intoxicated users' (had taken their OSM > 12 h ago, n = 20) and compared with opioid-naïve controls (n = 24). Empathy was assessed using the multifaceted empathy test and self-report questionnaire. Participants also underwent a period of social exclusion (Cyberball Game) and completed measures of mood and physiological responses (salivary cortisol and heart rate).

RESULTS

Non-intoxicated users had significantly lower emotional empathy (the ability to experience others' emotions), as well as greater anger after social exclusion when compared with the intoxicated users and controls. Anger did not change with social exclusion in the intoxicated user group and cortisol levels were lower overall.

CONCLUSIONS

Reduced ability to spontaneously share the emotions of others was reported in non-intoxicated users, particularly regarding positive emotions. There was some support for the idea of hyperalgesia to social pain, but this was restricted to an enhanced anger response in non-intoxicated users. Equivalent rates of empathy between the intoxicated users and controls could indicate some remediating effects of acute opioids.

Hair Analysis: Contamination versus Incorporation from the Circulatory System-Investigations on Single Hair Samples Using Time-of-Flight Secondary Ion Mass Spectrometry and Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Contamination is a highly controversial issue in hair analysis. Therefore, hair testing protocols typically include wash steps to remove contamination. However, recent studies claim that washing could also lead to permanent incorporation of contaminants into hair, thus questioning the validity of hair testing at all. In the present study, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) with longitudinal sectioning of single hairs and different decontamination protocols was used to reveal differences between the incorporation of a substance into hair from external sources and an incorporation via bloodstream. Single hairs were longitudinally sectioned using a custom-made sample holder. Data were acquired with MALDI-MS by rastering each hair individually. Single hair samples from drug users, blank hairs, and zolpidem- and zolpidem-D6-soaked hairs were investigated. Different published washing protocols were tested, and an in-house washing protocol was developed. For images with higher spatial resolution, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used. Longitudinal sectioning of hairs dramatically increased sensitivity; even single-dose administrations of zolpidem in single hairs could thus be detected using MALDI-MS. Zolpidem from external sources could be detected in large quantities in superficial hair structures. Zolpidem from consumer hairs, proposed to be strongly bound to inner hair structures, could not be completely removed even by the strongest tested decontamination protocol, whereas zolpidem-soaked hairs could be cleared almost completely with the developed in-house wash protocol. The applied methods allowed a first insight into the connection of decontamination protocols and wash-in phenomena in hair analysis. Further studies with other drugs are necessary to assess the general validity of these findings.