Why we should consider sex (and study sex differences) in addiction research

Good Practice Guideline for Preclinical Alcohol Research: The STRINGENCY Framework

Research in the field of preclinical alcohol research, but also science in general, has a problem: Many published scientific results cannot be repeated. As a result, findings from preclinical research often do not translate well to humans, causing increasing disappointment and calls for restructuring of preclinical research, that is, better reproducibility of preclinical research. However, the replication crisis is an inherent problem in biomedical research. Replication failures are not only due to small experimental variations but are often the result of poor methodology. In response to the replication crisis, numerous guidelines and recommendations have been proposed to promote transparency, rigor, and reproducibility in scientific research. What is missing today is a framework that integrates all the confusing information that results from all these guidelines and recommendations. Here we present STRINGENCY, an integrative approach to good practice guidelines for preclinical alcohol research, which can also apply to behavioral research in general and which aims to improve preclinical research to better prepare it for translation and minimize the "valley of death" in translational research. STRINGENCY includes systematic review and, when possible, meta-analysis prior to study design, sample size calculation, preregistration, multisite experiments, scientific data management (FAIR), reporting of data using ARRIVE, generalization of research data, and transparent publications that allow reporting of null results. We invite the scientific community to adopt STRINGENCY to improve the reliability and impact of preclinical alcohol research.

Association Study of Serotonin 1A Receptor Gene, Personality, and Anxiety in Women with Alcohol Use Disorder

Alcohol use disorder is considered a chronic and relapsing disorder affecting the central nervous system. The serotonergic system, mainly through its influence on the mesolimbic dopaminergic reward system, has been postulated to play a pivotal role in the underlying mechanism of alcohol dependence. The study aims to analyse the association of the rs6295 polymorphism of the 5HTR1A gene in women with alcohol use disorder and the association of personality traits with the development of alcohol dependence, as well as the interaction of the rs6295, personality traits, and anxiety with alcohol dependence in women. The study group consisted of 213 female volunteers: 101 with alcohol use disorder and 112 controls. NEO Five-Factor and State-Trait Anxiety Inventories were applied for psychometric testing. Genotyping of rs6295 was performed by real-time PCR. We did not observe significant differences in 5HTR1A rs6295 genotypes (p = 0.2709) or allele distribution (p = 0.4513). The AUD subjects scored higher on the anxiety trait (p < 0.0001) and anxiety state (p < 0.0001) scales, as well as on the neuroticism (p < 0.0001) and openness (p = 0134) scales. Significantly lower scores were obtained by the AUD subjects on the extraversion (p < 0.0001), agreeability (p < 0.0001), and conscientiousness (p < 0.0001) scales. Additionally, we observed a significant effect of 5HTR1A rs6295 genotype interaction and alcohol dependency, or lack thereof, on the openness scale (p = 0.0016). In summary, this study offers a comprehensive overview of alcohol dependence among women. It offers valuable insights into this complex topic, contributing to a more nuanced understanding of substance use among this specific demographic. Additionally, these findings may have implications for developing prevention and intervention strategies tailored to individual genetic and, most importantly, personality and anxiety differences.

Family history of substance problems among African Americans: Associations with drug use, drug use disorder, and prescription drug misuse

A family history of substance problems is a well-known risk factor for substance use and use disorders; however, much of this research has been conducted in studies with predominantly White subjects. The aim of this study was to examine the associations between family history density of substance problems and drug use, risk for drug use disorder, and prescription drug misuse in a sample of African American adults. Results indicate that family history density of substance problems increased the risk for all drug outcomes in the full sample. However, when subgroup analyses by gender were conducted, family history was not a risk factor among men for prescription drug misuse.

Subregion specific neuroadaptations in the female rat striatum during acute and protracted withdrawal from nicotine

Epidemiological studies and clinical observations suggest that nicotine, a major contributor of the global burden of disease, acts in a partially sex specific manner. Still, preclinical research has primarily been conducted in males. More research is thus required to define the effects displayed by nicotine on the female brain. To this end, female rats received 15 injections of either nicotine (0.36mg/kg) or saline, over a 3-week period and were then followed for up to 3 months. Behavioral effects of nicotine were assessed using locomotor activity measurements and elevated plus maze, while neurophysiological changes were monitored using ex vivo electrophysiological field potential recordings conducted in subregions of the dorsal and ventral striatum. Behavioral assessments demonstrated a robust sensitization to the locomotor stimulatory properties of nicotine, but monitored behaviors on the elevated plus maze were not affected during acute (24 h) or protracted (3 months) withdrawal. Electrophysiological recordings revealed a selective increase in excitatory neurotransmission in the nucleus accumbens shell and dorsomedial striatum during acute withdrawal. Importantly, accumbal neuroadaptations in nicotine-treated rats correlated with locomotor behavior, supporting a role for the nucleus accumbens in behavioral sensitization. While no sustained neuroadaptations were observed following 3 months withdrawal, there was an overall trend towards reduced inhibitory tone. Together, these findings suggest that nicotine produces selective transformations of striatal brain circuits that may drive specific behaviors associated with nicotine exposure. Furthermore, our observations suggest that sex-specificity should be considered when evaluating long-term effects by nicotine on the brain.

The stigma of smoking among women: A systematic review

BACKGROUND

Smoking stigma has been well documented, but little is known regarding its specific features and effects on women. Notably, women face unique social, cultural, and economic challenges that may interact with smoking stigma and impact health outcomes. This review investigates the extent to which smoking women encounter and internalise stigma, while examining the various coping mechanisms they employ to manage these negative experiences.

METHODS

In November 2022, major databases were systematically searched with no time restrictions. After applying inclusion and exclusion criteria, 23 studies (three quantitative and 20 qualitative) met our criteria. We conducted a quality assessment and summarised the findings pertaining to public stigma, self-stigma, and coping strategies.

RESULTS

The stigma about smoking emerges from a variety of sources, such as family, healthcare providers, or internet forums. Women smokers are universally aware of the negative image they have in society. Yet, their experiences and management of the stigma of smoking are shaped by other variables such as cultural background, social class, or motherhood status. Smoking stigma produces ambivalent effects, such as concealment, reduced usage of support services, and to a lesser extent, smoking cessation motivation.

CONCLUSIONS

These results indicate that smoking stigma is an important social justice and public health issue and that further research is needed to better prevent its effects on women's well-being and health behaviours.

Measurement invariance of the Marijuana Motives Measure among men and women using Stop Cannabis App

BACKGROUND

Motives to use cannabis play a central role in the development and maintenance of problematic cannabis use and previous studies stressed sex-related differences on motives to use cannabis. However, motives cannot be validly compared in men and women without first establishing the measurement invariance across sex. Therefore, the aim of the study is to (1) examine for the first time the measurement and structural invariance of the Marijuana Motives Measure (MMM) across sex, and (2) to investigate the motives for cannabis use that best explain problematic use.

METHODS

2951 (41.7% women) users of the "Stop cannabis" smartphone app of which 99.8% reported having used cannabis in the last three months completed an online MMM and ASSIST to assess the severity of their problematic cannabis use.

RESULTS

Multigroup confirmatory factor analyses supported measurement invariance across sex, whereas structural invariance was not confirmed. Indeed, group comparisons indicated that women reported greater coping motives then men whereas men showed greater social motives than women. A multiple linear regression analysis showed that only coping and conformity motives were significantly associated with greater problematic cannabis use, whereas neither sex nor the sex by motives interactions were significantly related to problematic cannabis use.

CONCLUSIONS

The MMM appears to function comparably across men and women. Therefore, sex-related comparisons on the questionnaire can be considered valid. Coping and conformity motives may play a central role part in the development of marijuana use problems which may hold implications for intervention development and public policy.

The effect of repetitive transcranial magnetic stimulation on electroencephalography microstates of patients with heroin-addiction

The effects of transcranial magnetic stimulation in treating substance use disorders are gaining attention; however, most existing studies used subjective measures to examine the treatment effects. Objective electroencephalography (EEG)-based microstate analysis is important for measuring the efficacy of transcranial magnetic stimulation in patients with heroin addiction. We investigated dynamic brain activity changes in individuals with heroin addiction after transcranial magnetic stimulation using microstate indicators. Thirty-two patients received intermittent theta-burst stimulation (iTBS) over the left dorsolateral prefrontal cortex. Resting-state EEG data were collected pre-intervention and 10 days post-intervention. The feature values of the significantly different microstate classes were computed using a K-means clustering algorithm. Four EEG microstate classes (A-D) were noted. There were significant increases in the duration, occurrence, and contribution of microstate class A after the iTBS intervention. K-means classification accuracy reached 81.5%. The EEG microstate is an effective improvement indicator in patients with heroin addiction treated with iTBS. Microstates were examined using machine learning; this method effectively classified the pre- and post-intervention cohorts among patients with heroin addiction and healthy individuals. Using EEG microstate to measure heroin addiction and further exploring the effect of iTBS in patients with heroin addiction merit clinical investigation.

Persistent Neuroadaptations in the Nucleus Accumbens Core Accompany Incubation of Methamphetamine Craving in Male and Female Rats

Relapse is a major problem in treating methamphetamine use disorder. "Incubation of craving" during abstinence is a rat model for persistence of vulnerability to craving and relapse. While methamphetamine incubation has previously been demonstrated in male and female rats, it has not been demonstrated after withdrawal periods greater than 51 d and most mechanistic work used males. Here, we address both gaps. First, although methamphetamine intake was higher in males during self-administration training (6 h/d × 10 d), incubation was similar in males and females, with "incubated" craving persisting through withdrawal day (WD)100. Second, using whole-cell patch-clamp recordings in medium spiny neurons (MSNs) of the nucleus accumbens (NAc) core, we assessed synaptic levels of calcium-permeable AMPA receptors (CP-AMPARs), as their elevation is required for expression of incubation in males. In both sexes, compared with saline-self-administering controls, CP-AMPAR levels were significantly higher in methamphetamine rats across withdrawal, although this was less pronounced in WD100-135 rats than WD15-35 or WD40-75 methamphetamine rats. We also examined membrane properties and NMDA receptor (NMDAR) transmission. In saline controls, MSNs from males exhibited lower excitability than females. This difference was eliminated after incubation because of increased excitability of MSNs from males. NMDAR transmission did not differ between sexes and was not altered after incubation. In conclusion, incubation persists for longer than previously described and equally persistent CP-AMPAR plasticity in NAc core occurs in both sexes. Thus, abstinence-related synaptic plasticity in NAc is similar in males and females although other methamphetamine-related behaviors and neuroadaptations show differences.

Prelimbic Cortex Activity during a Distress Tolerance Task Predicts Cocaine-Seeking Behavior in Male, But Not Female Rats

Distress tolerance (DT) is defined as the ability to persist in challenging goal-directed behavior in the face of stress, and individuals with low DT exhibit heightened drug-seeking behavior. However, no preclinical studies have examined the neurobiology underlying this phenomenon. To assess this, in vivo electrophysiology was used in Long Evans male and female rats during a DT task to record neural activity in the prelimbic cortex (PrL), a brain region implicated in drug-seeking. Rats were first assessed for DT, defined as the amount of time elapsed before rats quit seeking reward in an increasingly difficult operant task. Subsequently, rats underwent 2 weeks of self-administration for either water/saline or cocaine for 6 h/day. Animals then began a 1 month period of experimenter-imposed abstinence to induce heightened drug-seeking behavior. On day 28 of abstinence, DT and neural activity were reassessed; and on day 30, cocaine-seeking behavior was examined under extinction. Males had significantly higher DT than females and exhibited significantly more phasic PrL activity during the DT task. Furthermore, in male rats with a history of cocaine, PrL activity shifted to track DT; and this change in activity significantly correlated with the change in DT. Additionally, male (but not female) rats with low DT after 28 d of abstinence had significantly heightened drug-seeking behavior. Finally, PrL activity during the DT task predicted cocaine-seeking behavior. Collectively, these data demonstrate an important role for the PrL in DT in males, and link this neural activity and behavior to drug-seeking, particularly in males.SIGNIFICANCE STATEMENT Distress tolerance (DT) is defined as the ability to persist in challenging goal-directed behavior in the face of stress, and individuals with low DT exhibit heightened drug-seeking. Here, we investigated the role of the prelimbic cortex (PrL) in DT and its relationship to cocaine-seeking in male and female rats. We found that males had significantly higher DT than females and exhibited significantly more PrL activity during the DT task. Furthermore, male (but not female) rats with low DT after 28 d of abstinence had significantly heightened drug-seeking behavior. Finally, PrL activity during the DT task predicted cocaine-seeking. These data demonstrate an important role for the PrL in DT and link this neural activity and behavior to drug-seeking in males.

Adult alcohol drinking and emotional tone are mediated by neutral sphingomyelinase during development in males

Alcohol use, abuse, and addiction, and resulting health hazards are highly sex-dependent with unknown mechanisms. Previously, strong links between the SMPD3 gene and its coded protein neutral sphingomyelinase 2 (NSM) and alcohol abuse, emotional behavior, and bone defects were discovered and multiple mechanisms were identified for females. Here we report strong sex-dimorphisms for central, but not for peripheral mechanisms of NSM action in mouse models. Reduced NSM activity resulted in enhanced alcohol consumption in males, but delayed conditioned rewarding effects. It enhanced the acute dopamine response to alcohol, but decreased monoaminergic systems adaptations to chronic alcohol. Reduced NSM activity increased depression- and anxiety-like behavior, but was not involved in alcohol use for the self-management of the emotional state. Constitutively reduced NSM activity impaired structural development in the brain and enhanced lipidomic sensitivity to chronic alcohol. While the central effects were mostly opposite to NSM function in females, similar roles in bone-mediated osteocalcin release and its effects on alcohol drinking and emotional behavior were observed. These findings support the view that the NSM and multiple downstream mechanism may be a source of the sex-differences in alcohol use and emotional behavior.

A systematic review of gender-responsive and integrated substance use disorder treatment programs for women with co-occurring disorders

Background: Integrated and gender-responsive interventions, designed to target co-occurring substance use and psychiatric disorders in women, may be effective in addressing gender-specific challenges.Objectives: This systematic review aims to identify integrated gender-responsive substance use disorder treatments for women, summarize evaluations of these treatments, and address gaps in the literature.Methods: We searched PsycINFO, PubMed, and MEDLINE on September 24, 2021, and March 10, 2022. Included articles were randomized-controlled trials, secondary analyses of naturalistic studies, or open-label studies of integrated and gender-responsive treatments from any year that assessed both substance use and mental health/trauma outcomes.Results: We identified N = 24 studies (participants = 3,396; 100% women) examining Seeking Safety, Helping Women Recover and Beyond Trauma, A Woman's Path to Recovery, Modified Trauma Recovery and Empowerment Model (TREM), Breaking the Cycle, VOICES, Understanding and Overcoming Substance Misuse, Women's Recovery Group, Female Specific Cognitive Behavioral Therapy, and Moment by Moment in Women's Recovery. Across treatments there were significant improvements over time; Seeking Safety, Helping Women Recover, and TREM were associated with significantly better substance use and mental health outcomes relative to the comparison groups.Conclusions: Integrated gender-responsive treatments are a promising approach to treating women with co-occurring substance use and mental health concerns, and broad clinical implementation stands to benefit women. However, there remains a lack of studies evaluating substance use treatments in women with severe mental illness (e.g., psychotic-spectrum disorders) who differ in their needs and capacity.

A Qualitative Systematic Review of Experiences and Barriers Faced by Migrant Women with Perinatal Depression in Canada

Perinatal depression is the onset of depressive symptoms during pregnancy and up to one year after childbirth. Migrant women are at higher risk of experiencing perinatal depression due to numerous psychosocial stressors related to their experiences. This qualitative review aims to aggregate the experiences and barriers to care faced by immigrant and refugee women in Canada who have perinatal depression. Qualitative research can elucidate the barriers to treatment and culturally-impacted experiences of Canadian migrant women with perinatal depression. Following PRISMA and Joanna Briggs Institute (JBI) guidelines for conducting qualitative systematic reviews, 13 eligible studies representing 10 samples (N = 262 participants) were identified and included in this review. Participants included service providers, immigrant women, and refugee women. Three synthesized themes were identified by this review using the JBI meta-aggregative approach: (1) culture-related challenges; (2) migration-related challenges; and (3) service accessibility and quality. Within these themes were experiences of migrant women that encompass six categories: (1) conceptualization of perinatal depression; (2) childbirth-specific challenges; (3) migration-related challenges; (4) social isolation; (5) accessibility of services; and (6) quality of care. The role of family, cultural differences, financial challenges, and the effects of these on service accessibility are impactful in the experiences of migrant women. A greater understanding of the role of both culture and migration in the delivery of care, especially regarding service provider attitudes in more representative samples, is recommended.

Relationship between Depression and Cognitive Inhibition in Men with Heroin or Methamphetamine Use Disorder in First-Time Mandatory Detoxification

Previous studies have shown that males with substance use disorder (SUD) in their first mandatory detoxification experience high rates of depression. It is unknown whether this high depression incidence contributes to impaired inhibition. In this work, two studies were undertaken to examine the role of depression in cognitive inhibition in heroin and methamphetamine withdrawal. We used the Beck Depression Inventory (BDI) and the self-control scale (SCS) to explore the relationship between depression and impulse inhibition in patients participating in mandatory drug treatment for the first time (Study 1). The results showed that depression negatively predicted impulse inhibition. The Stroop color-word interference task was used to explore the role of patients' depression in their inhibitory abilities (Study 2). The results showed that the high-depression group had weaker inhibition performances in the Stroop color-word interference task compared to the low-depression group. This study shows that cognitive inhibition is weaker in people with high-depression addiction than in those with low depression. This result suggests that attention should be paid to the role of depressive comorbidity when conducting working memory training treatment for substance addiction.

Binge drinking indirectly predicts a negative emotional memory bias through coping motivations and depressive symptoms: The role of sex/gender

Background

In this three-part study, we investigate whether the associations between binge and problematic drinking patterns with a negative emotional memory bias (NMB) are indirectly related through coping motivations and depressive symptoms. We also address potential sex differences in these relations.

Methods

Participants (N = 293) completed the Timeline Followback to assess binge drinking, the Alcohol Use Disorder Identification Test (AUDIT) to assess problematic alcohol use, the Drinking Motives Questionnaire-Revised to assess coping motivations, and the Depression, Anxiety, and Stress Scales-21 to assess depression. Participants were asked to identify whether 30 emotional sentences were self-referent or not in an incidental encoding task; 24 h later they were asked to recall as many sentences as possible and a negative memory bias score was calculated.

Results

Across all three studies, we found significant bivariate relations between AUDIT scores, coping, depression, and an NMB, particularly for sentences participants deemed self-referent. In two undergraduate samples, there were significant indirect effects through coping motivations and depressive symptoms between binge drinking and an NMB in females as well as between AUDIT scores and an NMB in females only. In the community sample, there was only an indirect effect through coping motives, but this was observed in both females and males.

Conclusion

These findings support a relation between binge drinking as well as problematic alcohol use and a self-referent NMB in the context of coping motivations for alcohol use and depressive symptoms. Moreover, the pattern of findings suggests this model primarily holds for females, yet may also apply to males at higher levels of problematic alcohol use.

mGlu2 mechanism-based interventions to treat alcohol relapse

Recently we identified a deficiency in metabotropic glutamate receptor 2 (mGlu2) function in the corticoaccumbal pathway, as a common pathological mechanism underlying alcohol-seeking and relapse behavior. Based on this mechanism, we hypothesized that mGlu2/3 agonists and mGlu2 positive allosteric modulators (PAMs) may be effective in reducing relapse-like behavior. Two mGlu2/3 agonists, LY379268 and LY354740 (a structural analog of LY379268 six-fold more potent in activating mGlu2 over mGluR3), were tested in a well-established rat model of relapse, the alcohol deprivation effect (ADE) with repeated deprivation phases. Since these agonists do not readily discriminate between contributions of mGlu2 and mGluR3, we also tested LY487379, a highly specific PAM that potentiates the effect of glutamate on the mGlu2 with less specificity on other mGlu receptor subtypes. Both LY379268 and LY354740 significantly and dose-dependently reduced the expression of the ADE. No significant changes in water intake, body weight and locomotor activity were observed. Importantly, repeated administration of mGlu2/3 agonist did not lead to tolerance development. mGlu2 PAM LY487379 treatment significantly reduced expression of the ADE in both male and female rats. Combination treatment of mGlu2/3 agonist and PAM had similar effect on relapse-like drinking to that seen in mGlu2/3 agonist treatment alone. Together with other preclinical data showing that PAMs can reduce alcohol-seeking behavior we conclude that mGlu2 PAMs should be considered for clinical trials in alcohol-dependent patients.

Teaching About Sex and Gender in Neuroscience: More Than Meets the "XY"

Offering courses on the neuroscience of sex and gender can help support an inclusive curriculum in neuroscience. At the same time, developing and teaching such courses can be daunting to even the most enthusiastic educators, given the subject's complexities, nuances, and the difficult conversations that it invites. The authors of this article have all developed and taught such courses from different perspectives. Our aim is to provide educators with an overview of important conceptual topics as well as a comprehensive, but non-exhaustive, guide to resources for teaching about sex/gender in neuroscience based on our collective experience teaching courses on the topic. After defining vital terminology and briefly reviewing the biology of sex and sex determination, we describe some common topics within the field and contrast our current nuanced understandings from outdated misconceptions in the field. We review how (mis)representation of the neuroscience of sex/gender serves as a case study for how scientific results are communicated and disseminated. We consider how contextualization of sex/gender neuroscience research within a broader historical and societal framework can give students a wider perspective on the enterprise of science. Finally, we conclude with a brief discussion on how to choose learning goals for your course and implementation notes.

Barriers to Accessing Addiction Treatment for Women at Risk of Homelessness

Women remain under-represented in addiction treatment, comprising less than a third of clients in treatment services. Shame, stigma, and fear of legal and social repercussions (e.g., child protection involvement) are major barriers impacting on treatment-seeking for women. This is compounded for women at risk of homelessness, with practical and logistical reasons for not engaging in treatment. We conducted a qualitative study with both clinicians and service-providers, and women with lived experience of addiction and at risk of homelessness, to identify barriers to access and help-seeking within this vulnerable population. Adult women with lived experience of homelessness and addiction were invited to participate in an online focus group. Interviews were transcribed and analyzed using framework analysis. Analysis resulted in the identification of barriers to access in three areas. These were system-related, socio-cultural, and emotional barriers. We also present findings from the focus group recorded in real-time, using the novel method of digital illustration. This study highlights key factors impacting on help-seeking and access to treatment for addiction faced by women at risk of homelessness. The findings of this study highlight important areas of consideration for clinicians and service-providers working with women who experience addiction, as well as informing future research directions for this priority population. Findings are discussed in the context of exigent literature.

Sex Differences across Retrospective Transitions in Posttraumatic Stress and Substance Use Disorders

Objectives: Concurrent substance use disorder (SUD) and posttraumatic stress disorder (PTSD) occur at high rates and are typically associated with poor treatment outcomes in both sexes. However, women have a propensity to cope with increased negative affect via substance use in comparison to men; thus, it is important to elucidate the sex-specific bidirectional relationships between SUD and PTSD to improve our understanding of concurrent SUD/PTSD in men and women. Methods: Using data from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC-Wave 3; n = 36,309), the present study evaluated the impact of sex on the relationship between past-year SUDs (new, remitted, ongoing), including alcohol and drug use, and retrospective transitions in new vs. absent and ongoing vs. remitted diagnoses of PTSD. Additionally, the impact of sex was explored in models examining past year PTSD (new, remitted, ongoing) and retrospective transitions in new vs. absent and ongoing vs. remitted diagnosis of SUDs. Diagnostic transitions were based on retrospective reporting. Results: Results indicated that new, remitted, and ongoing SUDs increase the likelihood of new PTSD diagnoses (OR range = 2.53-8.11; p < 0.05). Among individuals with ongoing drug use disorders (DUD), there were greater odds of ongoing PTSD (OR = 2.10, p < 0.01). When examining the relationship reciprocally, new, remitted, and ongoing PTSD increased the likelihood of new SUDs (OR range = 2.50-8.22; p < 0.05), and ongoing PTSD increased the likelihood of ongoing SUD and DUD (OR = 1.40, 1.70, respectively; p < 0.05). Sex-specific analyses revealed that the relationship between PTSD and SUDs varies between sexes, particularly among women. For instance, women with new PTSD had higher odds of SUDs, and women with ongoing PTSD were almost 2.5 times more likely to have an ongoing DUD. Women with a new PTSD diagnosis were more likely to be diagnosed with a new SUD (OR = 3.27) and an ongoing DUD (OR = 3.08). Conclusions: Results indicate a bidirectional relationship between PTSD and SUD that is in many instances larger in women. Thus, illustrating potential sex-specific differences in underlying mechanisms implicated in SUD/PTSD, warranting additional research.

Effects of neonatal dopaminergic lesion on oral cocaine self-administration in rats: Higher female vulnerability to cocaine consumption

The dopaminergic system is associated with cocaine-seeking behaviors, being influenced by other neurotransmitters such as GABA and deregulated by chronic cocaine self-administration. Administration of 6-hydroxydopamine (6-OHDA) to neonatal rats produces a depletion of brain dopamine, mainly, that results in behavioral alterations in adulthood. This model can be applied to better understanding of the role of the dopaminergic system in cocaine use and how its behavioral effects can modulate drug intake. Though there are well-established sex differences in the pattern of drug use, there are no published studies investigating sex-dependent effects of neonatal lesions with 6-OHDA on cocaine self-administration nor regarding GABA_A receptor (GABA_AR) subunits expression. Herein, neurotoxic lesion was induced in male and female neonatal rats by intracisternal injection of 6-OHDA at PND 4, and locomotion was evaluated before and after cocaine self-administration. Cocaine was diluted in a sweet solution (sucrose 1.5%) and offered for 27 consecutive 3-h daily sessions via a dispenser for oral intake, in an operant chamber under a fixed-ratio 1 (FR1) schedule. The 6-OHDA lesion reduced oral cocaine self-administration in male and female rats. Female rats, independent of dopaminergic condition, consumed more cocaine-containing solution than sucrose-only solution. Furthermore, as expected, 6-OHDA-lesioned animals presented a higher basal locomotor activity when compared to sham rats. We evaluated GABA_AR subunit expression and found no statistically significant differences between rats that self-administered a sucrose-only solution and those that self-administered a cocaine-containing solution. Even when the reward system is depleted, some behavioral differences remain in females, providing more data that highlight the female vulnerability to cocaine consumption.

The Role of Context Conditioning in the Reinstatement of Responding to an Alcohol-Predictive Conditioned Stimulus

Re-exposure to an unconditioned stimulus (US) can reinstate extinguished conditioned responding elicited by a conditioned stimulus (CS). We tested the hypothesis that the reinstatement of responding to an appetitive CS is driven by an excitatory association formed between the US and the context that the US was ingested in during US re-exposure. Male, Long-Evans rats were acclimated to drinking alcohol (15%, v/v) in the home-cage, then trained to associate an auditory CS with an alcohol-US that was delivered into a fluid port for oral intake. During subsequent extinction sessions, the CS was presented as before, but without alcohol. After extinction, rats were re-exposed to alcohol as in training, but without the CS (alcohol re-exposure). 24h later at test, the CS was presented as in training, but without alcohol. First, we tested the effect of extinguishing the context-alcohol association, formed during alcohol re-exposure, on reinstatement. Conducting four context extinction sessions across four days (spaced extinction) after the alcohol re-exposure session did not impact reinstatement. However, four context extinction sessions conducted across two days (massed extinction) prevented reinstatement. Next, we conducted alcohol re-exposure in a context that either differed from, or was the same as, the test context. One alcohol re-exposure session in a different context did not affect reinstatement, however, three alcohol re-exposure sessions in a different context significantly reduced reinstatement during the first CS trial. These results partially support the view that a context-US association formed during US re-exposure drives the reinstatement of responding to an appetitive, alcohol-predictive CS.

A systematic review of the effect of ovarian sex hormones on stimulant use in females

Stimulant use disorder is associated with significant global health burden. Despite evidence for sex differences in the development and maintenance of stimulant use disorder, few studies have focused on mechanisms underpinning distinct trajectories in females versus males, including the effect of the ovarian sex hormones estrogen and progesterone. This review aimed to identify and synthesise the existing preclinical and clinical literature on the effect of ovarian sex hormones on stimulant consumption in females. A systematic search of peer-reviewed literature identified 1593 articles, screened using the following inclusion criteria: (1) adult female humans or animals, (2) using stimulant drugs, (3) ovarian sex hormones were administered exogenously OR were measured in a validated manner and (4) with stimulant consumption as an outcome measure. A total of 50 studies (3 clinical and 47 preclinical) met inclusion criteria. High-estrogen (low progesterone) phases of the menstrual/estrus cycle were associated with increased stimulant use in preclinical studies, while there were no clinical studies examining estrogen and stimulant consumption. Consistent preclinical evidence supported progesterone use reducing stimulant consumption, which was also identified in one clinical study. The review was limited by inconsistent data reporting across studies and different protocols across preclinical laboratory paradigms. Importantly, almost all studies examined cocaine use, with impact on methamphetamine use a significant gap in the existing evidence. Given the safety and tolerability profile of progesterone, further research is urgently needed to address this gap, to explore the potential therapeutic utility of progesterone as a treatment for stimulant use disorder.

Post-legalization changes in marijuana use in a sample of young California adults

INTRODUCTION

Increasing marijuana use among young adults is a concern due to substantial acute and chronic health risks. More widespread use of marijuana may also lead to increased use of nicotine and tobacco products. California legalized commercial sales of marijuana for recreational use as of January 2018. To our knowledge no studies to date have examined subsequent changes in marijuana use. The goal of this study was to test the hypothesis that marijuana use frequency increased following legalization of recreational sales. We also hypothesized that increased marijuana frequency would predict greater frequency of nicotine/tobacco consumption.

METHODS

The study was a secondary analysis of a longitudinal study of tobacco use among non-daily cigarette smokers. Participants were 563 young adults (aged 18-24) enrolled in 2015-16 and followed quarterly for 3 years.

RESULTS

A piecewise multilevel regression model indicated that marijuana use frequency did not change over time, including following legalization. More frequent use was associated with younger age and identifying as white (ps < 0.001, which did not change after legalization. Marijuana frequency was moderated by sex (p < .001), with women reporting increasing and men decreasing use over time. It was also associated with tobacco use, and particularly with e-cigarette use following legalization (ps < 0.05).

CONCLUSIONS

Findings suggest legalization of recreational marijuana sales had a negligible overall impact on days of use among young adults, but may have prompted increased interest in marijuana among some, particularly women and e-cigarette users. The continuously evolving landscape around these products indicates that ongoing surveillance is critical.

Female mice are more prone to develop an addictive-like phenotype for sugar consumption

The concept of “sugar addiction” is gaining increasing attention in both the lay media and scientific literature. However, the concept of sugar addiction is controversial and only a few studies to date have attempted to determine the “addictive” properties of sugar using rigorous scientific criteria. Here we set out to systematically test the addictive properties of sugar in male and female mice using established paradigms and models from the drug addiction field. Male and female C57BL/6N (8–10 weeks old) were evaluated in 4 experimental procedures to study the addictive properties of sugar: (i) a drinking in the dark (DID) procedure to model sugar binging; (ii) a long-term free choice home cage drinking procedure measuring the sugar deprivation effect (SDE) following an abstinence phase; (iii) a long-term operant sugar self-administration with persistence, motivation and compulsivity measures and (iv) intracranial self-stimulation (ICSS). Female mice were more vulnerable to the addictive properties of sugar than male mice, showing higher binge and long-term, excessive drinking, a more pronounced relapse-like drinking following deprivation, and higher persistence and motivation for sugar. No sex differences were seen in a compulsivity test or reward sensitivity measured using ICSS following extended sugar consumption. This study demonstrates the occurrence of an addictive-like phenotype for sugar in male and female mice, similar to drugs of abuse, and suggests sex-dependent differences in the development of sugar addiction.

No changes in the oxytocin system in alcohol-dependent female rodents and humans: Towards a sex-specific psychopharmacology in alcoholism

A pronounced decrease of oxytocin and increase of oxytocin receptor binding sites were recently reported in male alcohol dependent rats and male alcohol dependent patients. Here we comment on this and emphasize that in female alcohol dependent rats and humans no changes occur in the oxytocin system. We therefore suggest specific intervention with oxytocin only in male subjects.

A Gender Perspective of Addictive Disorders

Purpose of Review

Substance use disorders (SUD) affect differentially women and men. Although the prevalence has been reported higher in men, those women with addictive disorders present a more vulnerable profile and are less likely to enter treatment than men. The aim of this paper is to present an overview of how sex and gender may influence epidemiology, clinical manifestations, social impact, and the neurobiological basis of these differences of women with SUD, based on human research.

Recent Findings

The differences in prevalence rates between genders are getting narrower; also, women tend to increase the amount of consumption more rapidly than men, showing an accelerated onset of the SUD (telescoping effect). In respect to clinical features, the most important differences are related to the risk of experience psychiatric comorbidity, the exposure to intimate partner violence, and the associated high risks in sexual and reproductive health; and those who are mothers and addicted to substances are at risk of losing the custody of children accumulating more adverse life events. Some of these differences can be based on neurobiological differences: pharmacokinetic response to substances, sensitivity to gonadal hormones, differences in neurobiological systems as glutamate, endocannabinoids, and genetic differences.

Summary

Specific research in women who use drugs is very scarce and treatments are not gender-sensitive oriented. For these reasons, it is important to guarantee access to the appropriate treatment of women who use drugs and a need for a gender perspective in the treatment and research of substance use disorders.

Genetically selected alcohol-preferring msP rats to study alcohol use disorder: Anything lost in translation?

For several decades, genetically selected alcohol-preferring rats have been successfully used to mimic and study alcohol use disorders (AUD). These rat lines have been instrumental in advancing our understanding of the neurobiology of alcoholism and enabling pharmacological studies to evaluate drug efficacy on alcohol drinking and relapse. Moreover, the results of these studies have identified genetic variables that are linked to AUD vulnerability. This is an up-to-date review that focuses on genetically selected Marchigian Sardinian alcohol-preferring (msP) rats. To support the translational relevance of the findings that are obtained from msP rats and highlight important similarities to AUD patients, we also discuss the results of recent brain imaging studies. Finally, to demonstrate the importance of studying sex differences in animal models of AUD, we present original data that highlight behavioral differences in the response to alcohol in male and female rats. Female msP rats exhibited higher alcohol consumption compared with males. Furthermore, msP rats of both sexes exhibit higher anxiety- and depressive-like behaviors in the elevated plus maze and forced swim test, respectively, compared with unselected Wistar controls. Notably, voluntary alcohol drinking decreases foot-shock stress and depressive-like behavior in both sexes, whereas anxiety-like behavior in the elevated plus maze is attenuated only in males. These findings suggest that male and female msP rats both drink high amounts of alcohol to self-medicate negative affective symptoms. For females, this behavior may be driven by an attempt to treat stress and depressive-like conditions. For males, generalized anxiety appears to be an important additional factor in the motivation to drink alcohol. This article is part of the special issue on 'Vulnerabilities to Substance Abuse.'

Transient serotonin depletion at adolescence, but not at early infancy, reduced subsequent anxiety-like behavior and alcohol intake in female mice

RATIONALE

Serotonin (5-HT) plays an important role in the organization of the central nervous system and in the development of social interaction deficits and psychiatric disorders, including anxiety, depression, and addiction disorders. Notably, disruption of the 5-HT system during sensitive periods of development exerts long-term consequences, including altered anxiety response and problematic use of alcohol.

OBJECTIVE

we analyzed, in mice, the effects of transient 5-HT depletion at infancy or adolescence on subsequent anxiety-like behavior and alcohol intake during adolescence.

METHODS

C57/BL6 male and female mice were administered a 5-HT synthesis inhibitor (PCPA; 4-chloro-DL-phenylalanine methyl ester hydrochloride) at infancy (postnatal days 14-16 [PD14-16]) or adolescence (PD40-42). Eleven (± 1) days after treatment, mice were assessed for ethanol intake in daily two-bottle choice tests and for anxiety response via the elevated plus maze.

RESULTS

Female, but not male, mice transiently depleted of 5-HT at adolescence (but not those depleted at the perinatal stage) exhibited a significant reduction in anxiety response, which was accompanied by a significant reduction on alcohol intake.

CONCLUSION

Transient 5-HT inhibition at adolescence may act, in females, as a protective factor for the emergence of anxiety disorders and problematic use of alcohol during adolescence.

Derivation and assessment of the opioid use disorder severity scale: prediction of health, psychological and social adjustment problems

Background: Severity of substance use disorder (SUD) is typically evaluated by tabulating the number of symptoms. The resulting estimate of disorder severity is, however, biased due to intercorrelations among symptoms and their unequal salience. Objective. Employing item response theory (IRT) methodology, opioid use disorder symptoms were calibrated to derive the Opioid Use Disorder Severity Scale (OUDSS) and assess its predictive ability in men and women separately. Methods: A two-parameter IRT model was utilized to derive the OUDSS from DSM-IV symptoms recorded on the Structured Clinical Interview for DSM-IV (SCID) in 438 men and 429 women who reported at least one lifetime opioid consumption event. The predictive ability of the OUDSS was evaluated using the 10 health, psychological, and social adjustment domains of the revised Drug Use Screening Inventory (DUSI-R) assessed 2 years later. Results: The OUDSS score predicted the severity of problems in all 10 DUSI-R domains in men and women. The OUDSS also predicted the DUSI-R diagnostic cutoff score of overall problem density score in men and women (OR = 2.21 and OR = 4.83, respectively). Withdrawal was the most frequently endorsed symptom in this sample of opioid users. The other symptoms' frequencies, while somewhat lower than withdrawal's, did not differ from it substantially, indicating a similar severity threshold. Conclusions: OUDSS enables dimensional measurement of opioid use severity on an interval scale. The OUDSS and DUSI-R together can identify problem areas requiring prevention or treatment.

Forecasting Opioid Use Disorder at 25 Years of Age in 16-Year-Old Adolescents

OBJECTIVE

To evaluate the accuracy of detecting 16-year-old male (n = 465) and female (n = 162) youths who subsequently manifest opioid use disorder (OUD) at 25 years of age. We hypothesized that the combined measures of 2 components of etiology, heritable risk, and substance use, accurately detect youths who develop OUD.

STUDY DESIGN

Heritable risk was measured by the transmissible liability index (TLI). Severity of the prodrome presaging OUD was quantified by the revised Drug Use Screening Inventory containing the consumption frequency index (CFI) documenting substance use events during the past month and the overall problem density (OPD) score indicating co-occurring biopsychosocial problems. Diagnosis of OUD was formulated by a clinical committee based on results of the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition in conjunction with medical and social history records.

RESULTS

Bivariate analysis shows that the TLI, CFI, and OPD scores at 16 years of age predict OUD at 25 years. Multivariate modeling indicates that the TLI combined with the CFI predict OUD with 86% accuracy (sensitivity = 87%; specificity = 62%). The TLI and CFI at 16 years of age mediate the association between parental substance use disorder and OUD in offspring at 25 years of age, indicating that these measures respectively evaluate risk and prodrome.

CONCLUSIONS

These results demonstrate the feasibility of identifying youths requiring intervention to prevent OUD.

Impulsivity across substance use categories: Consideration of sex/gender

PURPOSE OF REVIEW

The goal was to review recent (1/2015-2/2020) evidence of impulsivity as a feature of substance use disorders or use of substances (alcohol, cannabis, nicotine, opioids, stimulants) in males compared to females in terms of: a) impulsivity in substance-using groups (or substance-using compared to control groups), and b) relationship between impulsivity and substance use behavior, clinical severity, or treatment outcomes.

RECENT FINDINGS

Of 361 papers identified by the searches, 69 met inclusion criteria, and 39 were highlighted for considering sex/gender in relation to impulsivity in substance-using populations. Taken together, findings supported higher impulsivity in males and females who use substances, relative to controls; and higher impulsivity was linked with more substance use/severity in both sex/genders. There were mixed findings regarding male versus female differences in impulsivity among individuals who use substances, or in the magnitude of the relationship between impulsivity and substance use severity.

SUMMARY

The current body of evidence does not point to a consistent sex/gender difference in the role of impulsivity within and across substance use disorders. Impulsivity is a clinically-relevant construct for male and female individuals who use substances, across a range of substances.

Males are more sensitive to reward and less sensitive to loss than females among people with internet gaming disorder: fMRI evidence from a card-guessing task

BACKGROUND

Many studies have found an interesting issue in the Internet gaming disorder (IGD): males are always observed to be the majority. However, there are little research to exploring the differences in the neural mechanisms between males and females in decision-making process among people with IGD. Therefore, explore the reward/loss processing between different gender with IGD could help in understanding the underlying neural mechanism of IGD.

METHODS

Data from functional magnetic resonance imaging (fMRI) were collected from 111 subjects (IGD: 29 males, 25 females; recreational internet game user (RGU): 36 males, 21 females) while they were performing a card-guessing task. We collected and compared their brain features when facing the win and loss conditions in different groups.

RESULTS

For winning conditions, IGD group showed hypoactivity in the lingual gyrus than RGU group, male players showed hyperactivity in the left caudate nucleus, bilateral cingulate gyrus, right middle frontal gyrus (MFG), right precuneus and inferior parietal lobule relative to the females. And significant sex-by-group interactions results showed higher brain activities in the thalamus, parahippocampal gyrus and lower brain activities in Inferior frontal gyrus (IFG) were observed in males with IGD than females. For losing conditions, IGD group showed hypoactivity in the left lingual gyrus, parahippocampal gyrus and right anterior cingulate cortex (ACC) compared to the RGU group, male players showed hyperactive left caudate nucleus and hypoactive right middle occipital gyrus relative to females. And significant sex-by-group interactions results showed that compared to females with IGD, males with IGD showed decreased brain activities in the IFG and lingual gyrus.

CONCLUSIONS

First, there appeared to be no difference in reward processing between the IGD and RGU group, but IGD showed less sensitivity to loss. Secondly, male players showed more sensitivity to rewards and less sensitivity to losses. Last but not least, males and females showed opposite activation patterns in IGD degree and rewards/losses processing. And male IGD subjects are more sensitive to reward and less sensitive to loss than females, which might be the reason for the gender different rates on IGD.

Psilocybin and LSD have no long-lasting effects in an animal model of alcohol relapse

For most psychiatric disorders, including alcohol use disorder (AUD), approved pharmacological treatments are limited in their effectiveness, and new drugs that can easily be translated into the clinic are needed. Currently, great hope lies in the potential of psychedelics to effectively treat AUD. The primary hypothesis is that a single session of psychedelic-guided psychotherapy can restore normal brain function in AUD individuals and thereby reduce the risk of relapse in the long run. Here we applied three different treatment schedules with psilocybin/LSD in order to investigate relapse-like drinking in the alcohol deprivation effect (ADE) model. In contrast to the primary hypothesis, psychedelics had no long-lasting effects on the ADE in male and female rats, neither when administered in a high dosage regime that is comparable to the one used in clinical studies, nor in a chronic microdosing scheme. Only sub-chronic treatment with psilocybin produced a short-lasting anti-relapse effect. However, it is not a translatable treatment option to give psychedelics sub-chronically for relapse prevention. In conclusion, our results in the ADE model do not support the hypothesis that microdosing or high doses of psychedelic reduce relapse behavior. This conclusion has to be confirmed by applying other animal models of AUD. It could also well be that animal models of AUD might be unable to fully capture the therapeutic potential of psychedelic drugs and that only future large-scale clinical trials will be able to demonstrate the efficacy of psychedelics as a new treatment option for AUD.

Decomposition of Mean Sex Differences in Alcohol Use Within a Genetic Factor Model

A wealth of literature suggests that normative and heavy alcohol consumption continue to follow a historical pattern of greater prevalence among males as compared to females. Some prior research suggested that sex-specific factors might explain some of this gender gap. Generally speaking, though, more recent studies have indicated that the sources of differences for most complex traits, both genetic and environmental, are similar for males and females. To the best of our knowledge, however, no studies have tested whether genetic and environmental factors common to both sexes are more often expressed in males, on average, thereby accounting for some of the mean sex difference in alcohol use. The current study used nationally representative data from American twin respondents and a multiple group genetic factor model with a mean structure to address this gap in the literature. Results provide no evidence of sex differences in covariance structure and suggest that genetic and nonshared environmental influences common to both sexes largely explain why male alcohol use is more frequent and severe, on average, than is female use. In contrast, shared environmental influences seem to play a less important role. We discuss our findings in the context of the existing literature and chart out directions for future research.

Filling the Regulatory Gap: Potential Role of Institutional Review Boards in Promoting Consideration of Sex as a Biological Variable

Consideration of sex differences in biomedical research is crucial to ensure the safety and effectiveness of drugs and devices for both sexes and to improve the rigor and reproducibility of scientific discoveries. Historically, women were underrepresented in clinical research and sex differences typically were not considered. The U.S. Food and Drug Administration (FDA) and the National Institutes of Health (NIH) have played a role in improving the representation of women in clinical trials and in encouraging the consideration of sex differences. As it is not appropriate for all studies to be reviewed by the FDA nor do all studies have NIH funding, this results in a regulatory gap. We propose that local institutional review boards (IRBs) and institutional animal care and use committees (IACUCs) provide greater oversight by encouraging researchers to consider sex as a biological variable (SABV) during protocol review. In this perspective article, we review how FDA and NIH policies have fostered change and highlight how IRBs and IACUCs could encourage investigators to consider SABV.

7,8-Dihydroxyflavone Enhances Cue-Conditioned Alcohol Reinstatement in Rats

Alcohol use disorder (AUD) is a detrimental disease that develops through chronic ethanol exposure. Reduced brain-derived neurotrophic factor (BDNF) expression has been associated with AUD and alcohol addiction, however the effects of activation of BDNF signalling in the brain on voluntary alcohol intake reinstatement and relapse are unknown. We therefore trained male and female Sprague Dawley rats in operant chambers to self-administer a 10% ethanol solution. Following baseline acquisition and progressive ratio (PR) analysis, rats were split into drug and vehicle groups during alcohol lever extinction. The animals received two weeks of daily IP injection of either the BDNF receptor, TrkB, agonist, 7,8-dihydroxyflavone (7,8-DHF), or vehicle. During acquisition of alcohol self-administration, males had significantly higher absolute numbers of alcohol-paired lever presses and a higher PR breakpoint. However, after adjusting for body weight, the amount of ethanol was not different between the sexes and the PR breakpoint was higher in females than males. Following extinction, alcohol-primed reinstatement in male rats was not altered by pretreatment with 7,8-DHF when adjusted for body weight. In contrast, in female rats, the weight-adjusted potential amount of ethanol, but not absolute numbers of active lever presses, was significantly enhanced by 7,8-DHF treatment during reinstatement. Analysis of spontaneous locomotor activity in automated photocell cages suggested that the effect of 7,8-DHF was not associated with hyperactivity. These results suggest that stimulation of the TrkB receptor may contribute to reward craving and relapse in AUD, particularly in females.

Long-term hippocampal interneuronopathy drives sex-dimorphic spatial memory impairment induced by prenatal THC exposure

Prenatal exposure to Δ⁹-tetrahydrocannabinol (THC), the most prominent active constituent of cannabis, alters neurodevelopmental plasticity with a long-term functional impact on adult offspring. Specifically, THC affects the development of pyramidal neurons and GABAergic interneurons via cannabinoid CB₁ receptors (CB₁R). However, the particular contribution of these two neuronal lineages to the behavioral alterations and functional deficits induced by THC is still unclear. Here, by using conditional CB₁R knockout mice, we investigated the neurodevelopmental consequences of prenatal THC exposure in adulthood, as well as their potential sex differences. Adult mice that had been exposed to THC during embryonic development showed altered hippocampal oscillations, brain hyperexcitability, and spatial memory impairment. Remarkably, we found a clear sexual dimorphism in these effects, with males being selectively affected. At the neuronal level, we found a striking interneuronopathy of CCK-containing interneurons in the hippocampus, which was restricted to male progeny. This THC-induced CCK-interneuron reduction was not evident in mice lacking CB₁R selectively in GABAergic interneurons, thus pointing to a cell-autonomous THC action. In vivo electrophysiological recordings of hippocampal LFPs revealed alterations in hippocampal oscillations confined to the stratum pyramidale of CA1 in male offspring. In addition, sharp-wave ripples, a major high-frequency oscillation crucial for learning and memory consolidation, were also altered, pointing to aberrant circuitries caused by persistent reduction of CCK⁺ basket cells. Taken together, these findings provide a mechanistic explanation for the long-term interneuronopathy responsible for the sex-dimorphic cognitive impairment induced by prenatal THC.

Within-animal comparisons of novelty and cocaine neuronal ensemble overlap in the nucleus accumbens and prefrontal cortex

Novelty seeking is a personality trait associated with an increased vulnerability for substance abuse. In rodents, elevated novelty seeking has been shown to be a predictor for elevated drug self-administration and compulsive use. While previous studies have shown that both novelty and drugs of abuse have actions within similar mesocorticolimbic regions, little is known as to whether the same neural ensembles are engaged by these two stimuli. Using the TetTag mouse model and Fos immunohistochemistry, we measured neurons engaged by novelty and acute cocaine exposure, respectively in the prefrontal cortex (PFC) and nucleus accumbens (NAc). While there was no significant impact of novelty exposure on the size of the EGFP+ ensemble, we found that cocaine engaged significantly more Fos+ neurons in the NAc, while stress increased the size of the Fos+ ensemble in the PFC. Analysis of ensemble reactivation was specific to the emotional valence of the second stimuli. We found that a greater proportion of the EGFP+ ensemble was reactivated in the groups that paired novelty with a positive (cocaine) or neutral (saline) experience in the NAc, while the novelty/stress paired groups exhibited significantly less ensemble overlap in the PFC. However, only in the NAc shell was this increase in ensemble overlap specific to those exposed to both novelty and cocaine. This suggests that the NAc shell, but not the NAc core or PFC, may play an important role in general reward processing by engaging a similar network of neurons.

Everything you always wanted to know about sex and dopamine, but were afraid to ask: An Editorial for 'No basal or drug-induced sex differences in striatal dopaminergic levels: a cluster and metaanalysis of rat microdialysis studies' on page 482

Behavioral neuroscience has taken a long time to finally recognize that the largely distinct behavioral repertoires of males and females may arise from differences in brain function. This may in particular apply for the neurochemistry of the dopamine systems and their roles in the organization of emotion, learning, and reinforcement in health and in pathological conditions. The current Editorial highlights a study by Egenrieder and colleagues published in the current issue of the Journal of Neurochemistry, in which the authors have analyzed extracellular dopamine neurochemistry from females and males in a meta-analysis. Largely surprising, they report that after detailed control of methodological differences between studies, no major differences in basal or drug-induced extracellular dopamine activity emerged between sexes in rodents. The locally dissociating effects of ovariectomy in females reported in the Egenrieder et al. study, may furthermore suggest that there may be different sex effects in the distinct dopaminergic projections of the mesolimbic and nigrostriatal dopamine system. However, this may only be the beginning of a system's analysis of dopaminergic sex differences that calls for further meta-analyses of the existing studies.

Transgenerational influence of parental morphine exposure on pain perception, anxiety-like behavior and passive avoidance memory among male and female offspring of Wistar rats

Accumulating evidence suggests that epigenetic mechanisms play an important role in the formation and maintenance of memory within the brain. Moreover, the effect of parental drug-exposure before gestation on behavioral state of offspring has been little studied. The main objective of the current study is to evaluate the effect of parental morphine exposure on avoidance memory, morphine preference and anxiety-like behavior of offspring. The total of 32 males and 32 females were used for mating. The animals were treated with morphine. The offspring according to their parental morphine treatment was divided into four groups (n=16) including paternally treated, maternally treated, both of parents treated and naïve animals. The pain perception, anxiety-like behavior, and avoidance memory were evaluated in the offspring. In the current study, the total of 256 offspring was used for the experiments (4 tasks × 4 groups of offspring × 8 female offspring × 8 male offspring). The finding revealed that the avoidance memory and visceral pain were reduced significantly in male and female offspring with at least one morphine-treated parent. Moreover, anxiety-like behavior was reduced significantly in the male offspring with at least one morphine-treated parent. While anxiety-like behavior was increased significantly in female offspring that were treated by morphine either maternally or both of parents. The data revealed that the endogenous opioid system may be altered in the offspring of morphine-treated parent(s), and epigenetic role could be important. However, analysis of variance signified the important role of maternal inheritance.

Sex differences in fear extinction

Despite the exponential increase in fear research during the last years, few studies have included female subjects in their design. The need to include females arises from the knowledge gap of mechanistic processes underlying the behavioral and neural differences observed in fear extinction. Moreover, the exact contribution of sex and hormones in relation to learning and behavior is still largely unknown. Insights from this field could be beneficial as fear-related disorders are twice as prevalent in women compared to men. Here, we review an up-to-date summary of animal and human studies in adulthood that report sex differences in fear extinction from a structural and functional approach. Furthermore, we describe how these factors could contribute to the observed sex differences in fear extinction during normal and pathological conditions.

Discovery of early life stress interacting and sex-specific quantitative trait loci impacting cocaine responsiveness

BACKGROUND AND PURPOSE

Addiction vulnerability involves complex gene X environment interactions leading to a pathological response to drugs. Identification of the genes involved in these interactions is an important step in understanding the underlying neurobiology and rarely have such analyses examined sex-specific influences. To dissect this interaction, we examined the impact of prenatal stress (PNS) on cocaine responsiveness in male and female mice of the BXD recombinant inbred panel.

EXPERIMENTAL APPROACH

BXD strains were subjected to timed mating and assigned to PNS or control groups. PNS dams were subjected to restraint stress (1-hr restraint, three times daily) starting between embryonic day (E) 11 and 14 and continued until parturition. Adult male and female, control and PNS offspring were tested for locomotor response to initial and repeated cocaine injections (sensitization) as well as cocaine-induced conditioned place preference (CPP).

KEY RESULTS

Strain, PNS, and sex interacted to modulate initial and sensitized cocaine-induced locomotion, as well as CPP. Moreover, a quantitative trait locus (QTL) interacting with PNS regulating initial locomotor response to cocaine (chromosome X, 37.91 to 50.95 Mb) was identified. Also PNS-independent, female-specific QTLs regulating CPP (chromosome 11, 65.50 to 81.31 Mb) and sensitized cocaine-induced locomotion (chromosome 16, 95.79 to 98.32 Mb) were identified. Publicly available mRNA expression data were utilized to identify cis-eQTL and transcript covariation with the behavioural phenotype to prioritize candidate genes; including Aifm1.

CONCLUSIONS AND IMPLICATIONS

These QTL encompass genes that may moderate genetic susceptibility to PNS and interact with sex to determine adult responsiveness to cocaine and addiction vulnerability.

LINKED ARTICLES

This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Prenatal cannabinoid exposure and altered neurotransmission

Marijuana is one of the most commonly used illicit drugs worldwide. In addition, use of synthetic cannabinoids is increasing, especially among adolescents and young adults. Although human studies have shown that the use of marijuana during pregnancy leads to adverse behavioral effects, such as deficiencies in attention and executive function in affected offspring, the rate of marijuana use among pregnant women is steadily increasing. Various aspects of human behavior including emotion, learning, and memory are dependent on complex interactions between multiple neurotransmitter systems that are especially vulnerable to alterations during the developmental period. Thus, exploration of neurotransmitter changes in response to prenatal cannabinoid exposure is crucial to develop an understanding of how homeostatic imbalance and various long-term neurobehavioral deficits manifest following the abuse of marijuana or other synthetic cannabinoids during pregnancy. Current literature confirms that vast alterations to neurotransmitter systems are present following prenatal cannabinoid exposure, and many of these alterations within the brain are region specific, time-dependent, and sexually dimorphic. In this review, we aim to provide a summary of observed changes to various neurotransmitter systems following cannabinoid exposure during pregnancy and to draw possible correlations to reported behavioral alterations in affected offspring.

Females are more vulnerable to Internet gaming disorder than males: Evidence from cortical thickness abnormalities

BACKGROUND

Male predominance is a well-known feature of Internet gaming disorder (IGD), with a reported male to female ratio of 3:1. Because of the overwhelming focus on males, little is known about the neural basis of sex differences in IGD, especially neuroanatomical features. Thus, investigations on sex differences with an adequate sample size are critical for improving the understanding of biological mechanisms underlying IGD.

METHODS

Structural magnetic resonance imaging data were acquired from 62 IGD subjects (29 males, 33 females) and 71 recreational game users (RGUs) (37 males, 34 females) with well-matched age and education levels. Group-by-sex interaction in cortical thickness was analyzed, and the correlations between cortical thickness and addiction severity were calculated.

RESULTS

We detected a group-by-sex interaction in the bilateral rostral middle frontal gyri (MFG), left superior frontal gyrus (SFG), left supramarginal gyrus (SMG), right posterior cingulate cortex (PCC), and right superior parietal lobule (SPL). Post-hoc analyses revealed that, compared with same-sex RGUs, male IGD subjects had increased cortical thickness and female IGD subjects had reduced cortical thickness beside their right PCC. By contrast, male IGD subjects had reduced cortical thickness and female IGD subjects had increased cortical thickness in their right PCC. Moreover, only females showed significant negative correlations between the cortical thickness and their self-reported cravings and Internet addiction test scores.

CONCLUSIONS

For female IGD subjects, the reduced cortical thickness, combined with the negative correlations of addiction severities, suggests the great effect created by IGD in the brain regions. Males and females may be affected differently by IGD, with females being more vulnerable to it.

Sex differences in neural mechanisms mediating reward and addiction

There is increasing evidence in humans and laboratory animals for biologically based sex differences in every phase of drug addiction: acute reinforcing effects, transition from occasional to compulsive use, withdrawal-associated negative affective states, craving, and relapse. There is also evidence that many qualitative aspects of the addiction phases do not differ significantly between males and females, but one sex may be more likely to exhibit a trait than the other, resulting in population differences. The conceptual framework of this review is to focus on hormonal, chromosomal, and epigenetic organizational and contingent, sex-dependent mechanisms of four neural systems that are known-primarily in males-to be key players in addiction: dopamine, mu-opioid receptors (MOR), kappa opioid receptors (KOR), and brain-derived neurotrophic factor (BDNF). We highlight data demonstrating sex differences in development, expression, and function of these neural systems as they relate-directly or indirectly-to processes of reward and addictive behavior, with a focus on psychostimulants and opioids. We identify gaps in knowledge about how these neural systems interact with sex to influence addictive behavior, emphasizing throughout that the impact of sex can be highly nuanced and male/female data should be reported regardless of the outcome.

Gender-related differences in cue-elicited cravings in Internet gaming disorder: The effects of deprivation

BACKGROUND

Online gaming has become a popular leisure activity, in which males more frequently develop Internet gaming disorder (IGD) compared to females. However, gender-related neurocognitive differences have largely not been systematically investigated in IGD.

METHODS

Cue-elicited-craving tasks were performed before game playing and immediately after deprivation operationalized as a forced break from gaming when the Internet was disconnected. Ninety-nine subjects with IGD (27 males and 22 females) or recreational game use (RGU; 27 males and 23 females) provided functional MRI and subjective data. Analyses investigating effects of group (IGD and RGU) × gender (male and female) at different times (pre-gaming, post-gaming, and post-pre) on cue-elicited craving and brain responses were performed. Correlations between brain responses and subjective measures were calculated.

RESULTS

In pre-, post-, and post-pre tests, significant gender-by-group interactions (p < .001, cluster size > 15 voxels) were observed in the left dorsolateral prefrontal cortex (DLPFC). Further analyses of the DLPFC cluster showed that in post-pre comparisons, results were related to less engagement of the DLPFC in IGD, especially in females. In addition, at post-test, significant interactions were observed in the caudate, as females with IGD showed greater activation as compared to those with RGU.

DISCUSSION

The results raise the possibility that women with RGU may show better executive control than men when facing gaming cues, which may provide resiliency against developing IGD; however, once they develop IGD, their gaming may impair their executive control and enhance their cravings for gaming, which may make it more difficult to quit gaming.

Sex differences of inflammation in target organs, induced by intraperitoneal injection of lipopolysaccharide, depend on its dose

Purpose

The aim of our research was to study sex differences and the severity of inflammatory changes in target organs and the peculiarities of immunological disorders when low and high doses of lipopolysaccharide (LPS) were administered to rats.

Methods

Male and female 2- to 3-month-old Wistar rats (200–250 g) were injected intraperitoneally with Escherichia coli LPS in one of two doses: 1.5 or 15 mg/kg. In a day after the LPS injection, we studied endotoxin, corticosterone, sex steroids, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activity levels in the serum; morphological disorders in the lung, liver, thymus, and spleen; ex vivo production of IL-2, IL-4, tumor necrosis factor (TNF), and interferon γ (IFNγ) by splenic cells activated by ConA; and relative amount of T- and B-lymphocytes in the peripheral blood.

Results

After the injection of low-dose LPS, the serum endotoxin level increased only in males and was combined with a more pronounced inflammatory response in the lungs and thymus and an increase in ALT and AST activity levels without any changes in corticosterone level. After the injection of high-dose LPS, the inflammatory and pathological changes in the target organs manifested as severe endotoxemia and sex differences of pathological changes in the lungs and liver were not revealed. The level of production of IL-2, IL-4, IFNγ, and TNF by splenic cells and the number of T-lymphocytes, including cytotoxic cells, in the peripheral blood, decreased in males, which is an evidence of a pronounced suppression of the immune response.

Conclusion

We have shown that the morphofunctional changes in the organs of the immune system in females and males, as well as the intensity of the sex differences of inflammation, depend on the severity of systemic inflammatory response, induced by different doses of LPS.

Cocaine differentially affects synaptic activity in memory and midbrain areas of female and male rats: an in vivo MEMRI study

Manganese enhanced magnetic resonance imaging (MEMRI) has been previously used to determine the effect of acute cocaine on calcium-dependent synaptic activity in male rats. However, there have been no MEMRI studies examining sex differences in the functional neural circuits affected by repeated cocaine. In the present study, we used MEMRI to investigate the effects of repeated cocaine on brain activation in female and male rats. Adult female and male rats were scanned at 4.7 Tesla three days after final treatment with saline, a single cocaine injection (15 mg kg^-1, i.p. × 1 day) or repeated cocaine injections (15 mg kg^-1, i.p. × 10 days). A day before imaging rats were provided with an i.p. injection of manganese chloride (70 mg kg^-1). Cocaine produced effects on MEMRI activity that were dependent on sex. In females, we observed that a single cocaine injection reduced MEMRI activity in hippocampal CA3, ventral tegmental area (VTA), and median Raphé, whereas repeated cocaine increased MEMRI activity in dentate gyrus and interpeduncular nucleus. In males, repeated cocaine reduced MEMRI activity in VTA. Overall, it appeared that female rats showed a general trend towards increase MEMRI activity with single cocaine and reduced activity with repeated exposure, while male rats showed a trend towards opposite effects. Our results provide evidence for sex differences in the in vivo neural response to cocaine, which involves primarily hippocampal, amygdala and midbrain areas.