Sex differences in impulsive and compulsive behaviors: a focus on drug addiction

Correlations of the CNR1 Gene with Personality Traits in Women with Alcohol Use Disorder

Alcohol use disorder (AUD) is a significant issue affecting women, with severe consequences for society, the economy, and most importantly, health. Both personality and alcohol use disorders are phenotypically very complex, and elucidating their shared heritability is a challenge for medical genetics. Therefore, our study investigated the correlations between the microsatellite polymorphism (AAT)n of the Cannabinoid Receptor 1 (CNR1) gene and personality traits in women with AUD. The study group included 187 female subjects. Of these, 93 were diagnosed with alcohol use disorder, and 94 were controls. Repeat length polymorphism of microsatellite regions (AAT)n in the CNR1 gene was identified with PCR. All participants were assessed with the Mini-International Neuropsychiatric Interview and completed the NEO Five-Factor and State-Trait Anxiety Inventories. In the group of AUD subjects, significantly fewer (AAT)n repeats were present when compared with controls (p = 0.0380). While comparing the alcohol use disorder subjects (AUD) and the controls, we observed significantly higher scores on the STAI trait (p < 0.00001) and state scales (p = 0.0001) and on the NEO Five-Factor Inventory Neuroticism (p < 0.00001) and Openness (p = 0.0237; insignificant after Bonferroni correction) scales. Significantly lower results were obtained on the NEO-FFI Extraversion (p = 0.00003), Agreeability (p < 0.00001) and Conscientiousness (p < 0.00001) scales by the AUD subjects when compared to controls. There was no statistically significant Pearson's linear correlation between the number of (AAT)n repeats in the CNR1 gene and the STAI and NEO Five-Factor Inventory scores in the group of AUD subjects. In contrast, Pearson's linear correlation analysis in controls showed a positive correlation between the number of the (AAT)n repeats and the STAI state scale (r = 0.184; p = 0.011; insignificant after Bonferroni correction) and a negative correlation with the NEO-FFI Openness scale (r = -0.241; p = 0.001). Interestingly, our study provided data on two separate complex issues, i.e., (1) the association of (AAT)n CNR1 repeats with the AUD in females; (2) the correlation of (AAT)n CNR1 repeats with anxiety as a state and Openness in non-alcohol dependent subjects. In conclusion, our study provided a plethora of valuable data for improving our understanding of alcohol use disorder and anxiety.

Measuring Compulsivity as a Self-Reported Multidimensional Transdiagnostic Construct: Large-Scale (N = 182,000) Validation of the Cambridge-Chicago Compulsivity Trait Scale

Compulsivity has potential transdiagnostic relevance to a range of psychiatric disorders, but it has not been well-characterized and there are few existing measures available for measuring the construct across clinical and nonclinical samples that have been validated at large population scale. We aimed to characterize the multidimensional latent structure of self-reported compulsivity in a population-based sample of British children and adults (N = 182,145) using the Cambridge-Chicago Compulsivity Trait Scale (CHI-T). Exploratory structural equation modeling provided evidence for a correlated two-factor model consisting of (a) Perfectionism and (b) Reward Drive dimensions. Evidence was obtained for discriminant validity in relation to the big five personality dimensions and acceptable test-retest reliability. The CHI-T, here validated at extremely large scale, is suitable for use in studies seeking to understand the correlates and basis of compulsivity in clinical and nonclinical participants. We provide extensive normative data to facilitate interpretation in future studies.

Impulsivity Drives Adolescents to Smoke and Drink: Gender Differences in the Mediating Effects of Resilience and Depression

High and rising rates of smoking and drinking among Chinese adolescents are contributing to increasingly serious physical and mental health issues. While impulsivity has been demonstrated to be significantly related to adolescent cigarette and alcohol use, little is known about the mechanisms behind this association. The current study focused on resilience and depressive symptoms as potential mediators of this link, exploring the indirect pathways connecting impulsivity to teenage tobacco and alcohol use. Possible gender differences in this indirect pathway were also explored. Participants were secondary school students from southern China (N = 3466; 49.2% were female; Mage = 14.18; SDage = 1.57). Results revealed that adolescents who were more impulsive used cigarettes and alcohol more frequently, and that this effect was partially mediated by lower resilience and more depressive symptoms. It is noteworthy that there were gender differences in this mediating effect, with the effect of impulsivity on cigarette use for girls being mediated by resilience and depressive symptoms, whereas this statistically significant association was not identified for boys. These findings show how adolescents' impulsivity drives them to smoke and drink, and also emphasize gender as a crucial consideration for intervening with adolescents' drinking and smoking behaviors.

Gender-Specific Interactions in a Visual Object Recognition Task in Persons with Opioid Use Disorder

Opioid use disorder (OUD)-associated overdose deaths have reached epidemic proportions worldwide over the past two decades, with death rates for men reported at twice the rate for women. Using a controlled, cross-sectional, age-matched (18-56 y) design to better understand the cognitive neuroscience of OUD, we evaluated the electroencephalographic (EEG) responses of male and female participants with OUD vs. age- and gender-matched non-OUD controls during a simple visual object recognition Go/No-Go task. Overall, women had significantly slower reaction times (RTs) than men. In addition, EEG N200 and P300 event-related potential (ERP) amplitudes for non-OUD controls were significantly larger for men, while their latencies were significantly shorter than for women. However, while N200 and P300 amplitudes were not significantly affected by OUD for either men or women in this task, latencies were also affected differentially in men vs. women with OUD. Accordingly, for both N200 and P300, male OUD participants exhibited longer latencies while female OUD participants exhibited shorter ones than in non-OUD controls. Additionally, robust oscillations were found in all participants during a feedback message associated with performance in the task. Although alpha and beta power during the feedback message were significantly greater for men than women overall, both alpha and beta oscillations exhibited significantly lower power in all participants with OUD. Taken together, these findings suggest important gender by OUD differences in cognitive processing and reflection of performance in this simple visual task.

Sex differences in externalizing and internalizing traits and ventral striatal responses to monetary loss

Ventral striatum (VS) processes rewarding and punishing stimuli. Women and men vary in externalizing and internalizing traits, which may influence neural responses to reward and punishment. To investigate sex differences in how individual traits influence VS responses to reward and punishment, we curated the data of the Human Connectome Project and identified 981 (473 men) subjects evaluated by the Achenbach Adult Self-Report Syndrome Scales. We processed the imaging data with published routines and extracted VS response (β) to win and to loss vs. baseline in a gambling task for correlation with externalizing and internalizing symptom severity. Men vs. women showed more severe externalizing symptoms and higher VS response to monetary losses (VS-loss β) but not to wins. Men but not women showed a significant, positive correlation between VS-loss β and externalizing traits, and the sex difference was confirmed by a slope test. The correlations of VS-loss vs. externalizing and of VS-win vs. externalizing and those of VS-loss vs. externalizing and of VS-loss vs. internalizing traits both differed significantly in slope, confirming its specificity, in men. Further, the sex-specific relationship between VS-loss β and externalizing trait did not extend to activities during exposure to negative emotion in the face matching task. To conclude, VS responses to loss but not to win and their correlation with externalizing rather than internalizing symptom severity showed sex differences in young adults. The findings highlight the relationship of externalizing traits and VS response to monetary loss and may have implications for psychological models of externalizing behaviors in men.

Abstinence from Escalation of Cocaine Intake Changes the microRNA Landscape in the Cortico-Accumbal Pathway

Cocaine administration alters the microRNA (miRNA) landscape in the cortico-accumbal pathway. These changes in miRNA can play a major role in the posttranscriptional regulation of gene expression during withdrawal. This study aimed to investigate the changes in microRNA expression in the cortico-accumbal pathway during acute withdrawal and protracted abstinence following escalated cocaine intake. Small RNA sequencing (sRNA-seq) was used to profile miRNA transcriptomic changes in the cortico-accumbal pathway [infralimbic- and prelimbic-prefrontal cortex (IL and PL) and nucleus accumbens (NAc)] of rats with extended access to cocaine self-administration followed by an 18-h withdrawal or a 4-week abstinence. An 18-h withdrawal led to differential expression (fold-change > 1.5 and p < 0.05) of 21 miRNAs in the IL, 18 miRNAs in the PL, and two miRNAs in the NAc. The mRNAs potentially targeted by these miRNAs were enriched in the following pathways: gap junctions, neurotrophin signaling, MAPK signaling, and cocaine addiction. Moreover, a 4-week abstinence led to differential expression (fold-change > 1.5 and p < 0.05) of 23 miRNAs in the IL, seven in the PL, and five miRNAs in the NAc. The mRNAs potentially targeted by these miRNAs were enriched in pathways including gap junctions, cocaine addiction, MAPK signaling, glutamatergic synapse, morphine addiction, and amphetamine addiction. Additionally, the expression levels of several miRNAs differentially expressed in either the IL or the NAc were significantly correlated with addiction behaviors. Our findings highlight the impact of acute and protracted abstinence from escalated cocaine intake on miRNA expression in the cortico-accumbal pathway, a key circuit in addiction, and suggest developing novel biomarkers and therapeutic approaches to prevent relapse by targeting abstinence-associated miRNAs and their regulated mRNAs.

Glucocorticoid Receptor-Regulated Enhancers Play a Central Role in the Gene Regulatory Networks Underlying Drug Addiction

Substance abuse and addiction represent a significant public health problem that impacts multiple dimensions of society, including healthcare, the economy, and the workforce. In 2021, over 100,000 drug overdose deaths were reported in the US, with an alarming increase in fatalities related to opioids and psychostimulants. Understanding the fundamental gene regulatory mechanisms underlying addiction and related behaviors could facilitate more effective treatments. To explore how repeated drug exposure alters gene regulatory networks in the brain, we combined capped small (cs)RNA-seq, which accurately captures nascent-like initiating transcripts from total RNA, with Hi-C and single nuclei (sn)ATAC-seq. We profiled initiating transcripts in two addiction-related brain regions, the prefrontal cortex (PFC) and the nucleus accumbens (NAc), from rats that were never exposed to drugs or were subjected to prolonged abstinence after oxycodone or cocaine intravenous self-administration (IVSA). Interrogating over 100,000 active transcription start regions (TSRs) revealed that most TSRs had hallmarks of bonafide enhancers and highlighted the KLF/SP1, RFX, and AP1 transcription factors families as central to establishing brain-specific gene regulatory programs. Analysis of rats with addiction-like behaviors versus controls identified addiction-associated repression of transcription at regulatory enhancers recognized by nuclear receptor subfamily 3 group C (NR3C) factors, including glucocorticoid receptors. Cell-type deconvolution analysis using snATAC-seq uncovered a potential role of glial cells in driving the gene regulatory programs associated with addiction-related phenotypes. These findings highlight the power of advanced transcriptomics methods to provide insight into how addiction perturbs gene regulatory programs in the brain.

Prevalence of and Factors Associated with Dietary Supplement Use in a Stratified, Random Sample of US Military Personnel: The US Military Dietary Supplement Use Study

BACKGROUND

About 50% of Americans and 70% of US military service members use dietary supplements (DSs).

OBJECTIVES

This cross-sectional survey examined current prevalence of and factors associated with DS use in service members.

METHODS

A stratified random sample of 200,000 service members from the Air Force, Army, Marine Corps, and Navy was obtained from military manpower records, and these service members were asked to complete a questionnaire on their DS use and personal characteristics. Chi-square statistics and multivariable logistic regression examined differences across various strata of demographic, lifestyle, and military characteristics.

RESULTS

About 18% of successfully contacted service members (n = 26,681) completed the questionnaire between December 2018 and August 2019 (mean ± SD age: 33 ± 8 y, 86% male). Overall, 74% reported using ≥1 DS/wk. Multivitamins/multiminerals were the most commonly used DSs (45%), followed by combination products (44%), proteins/amino acids (42%), individual vitamins/minerals (31%), herbals (20%), joint health products (9%), and purported prohormones (5%). In multivariable analysis, factors independently associated with DS use included female gender [OR (female/male): 1.91; 95% CI: 1.73, 2.11], older age [OR (≥40/18-24 y): 1.25; 95% CI: 1.08, 1.44], higher education level [OR (college degree/high school or less): 1.35; 95% CI: 1.19, 1.53], higher BMI [OR (≥30/<25 kg/m2): 1.37; 95% CI: 1.25, 1.52], more weekly resistance training [OR (>300/≤45 min/wk): 5.05; 95% CI: 4.55, 5.61], smokeless tobacco use [OR (user/nonuser): 1.30; 95% CI: 1.17, 1.44], higher alcohol intake [OR (≥72/0 mL/wk): 1.41; 95% CI: 1.29, 1.54], and higher military rank [OR (senior officer/junior enlisted): 1.26; 95% CI: 1.06, 1.51].

CONCLUSIONS

Compared with civilian data from the NHANES, service members were much more likely to use DSs and used different types of DSs, especially combination products and proteins/amino acids often used to purportedly enhance physical performance. Comparisons with previous military data suggest DS use has increased over time.

Drugs of Abuse Differentially Alter the Neuronal Excitability of Prefrontal Layer V Pyramidal Cell Subtypes

The medial prefrontal cortex (mPFC) plays an important role in regulating executive functions including reward seeking, task flexibility, and compulsivity. Studies in humans have demonstrated that drugs of abuse, including heroin, cocaine, methamphetamine, and alcohol, alter prefrontal function resulting in the consequential loss of inhibitory control and increased compulsive behaviors, including drug seeking. Within the mPFC, layer V pyramidal cells, which are delineated into two major subtypes (type I and type II, which project to subcortical or commissurally to other cortical regions, respectively), serve as the major output cells which integrate information from other cortical and subcortical regions and mediate executive control. Preclinical studies examining changes in cellular physiology in the mPFC in response to drugs of abuse, especially in regard to layer V pyramidal subtypes, are relatively sparse. In the present study, we aimed to explore how heroin, cocaine, methamphetamine, ethanol, and 3,4-methylenedioxypyrovalerone (MDPV) alter the baseline cellular physiology and excitability properties of layer V pyramidal cell subtypes. Specifically, animals were exposed to experimenter delivered [intraperitoneal (i.p.)] heroin, cocaine, the cocaine-like synthetic cathinone MDPV, methamphetamine, ethanol, or saline as a control once daily for five consecutive days. On the fifth day, whole-cell physiology recordings were conducted from type I and type II layer V pyramidal cells in the mPFC. Changes in cellular excitability, including rheobase (i.e., the amount of injected current required to elicit action potentials), changes in input/output curves, as well as spiking characteristics induced by each substance, were assessed. We found that heroin, cocaine, methamphetamine, and MDPV decreased the excitability of type II cells, whereas ethanol increased the excitability of type I pyramidal cells. Together, these results suggest that heroin, cocaine, MDPV, and methamphetamine reduce mPFC commissural output by reducing type II excitability, while ethanol increases the excitability of type I cells targeting subcortical structures. Thus, separate classes of abused drugs differentially affect layer V pyramidal subtypes in the mPFC, which may ultimately give rise to compulsivity and inappropriate synaptic plasticity underlying substance use disorders.

Time-dependent changes in striatal monoamine levels and gene expression following single and repeated amphetamine administration in rats

As drug addiction may result from pathological usurpations of learning and memory's neural mechanisms, we focused on the amphetamine-induced time-dependent neurochemical changes associated with neural plasticity. We used juvenile rats as the risk for drug abuse is higher during adolescence. Experiment 1 served to define the appropriate amphetamine dose and the neurochemical effects of a single administration. In experiment 2, rats received seven amphetamine or saline injections in the open-field test throughout a twelve-day period. We measured the mRNA levels of the brain-derived neurotrophic factor (BDNF), its tropomyosin receptor kinase B (TrkB), the cAMP response element-binding protein (CREB), the microRNA-132, the Rho GTPase-activating protein 32 (p250GAP), the corticotropin-releasing factor (CRF), and monoamines and amino-acids contents in the nucleus accumbens and the dorsal striatum 45, 90, and 180 min after the last injection. We found that amphetamine changed gene expression only at certain time points and in a dose and region-dependent manner. Repeated but not single administrations upregulated accumbal and striatal BDNF (180 min) and striatal pri-miR-132 (90 min) expression, while downregulated accumbal CREB levels (90 min). As only some drug users develop addiction, we compared brain parameters between low and high amphetamine responders. Prone subjects characterized by having reduced striatal 5-HT metabolism, higher accumbal BDNF and TrkB expression, and lower levels of CREB in the dorsal striatum and p250GAP in both regions. Thus, individual differences in drug-induced changes in neurotransmission and gene expression in nigrostriatal and mesolimbic dopaminergic pathways may underlie the plasticity adaptations associated with behavioral sensitization to amphetamine.

Increased prevalence of impulse control disorder symptoms in endocrine diseases treated with dopamine agonists: a cross-sectional study

INTRODUCTION

Impulse control disorders (ICDs) have been described as a side effect of dopamine agonists (DAs) in neurological as well as endocrine conditions. Few studies have evaluated the neuropsychological effect of DAs in hyperprolactinemic patients, and these have reported a relationship between DAs and ICDs. Our objective was to screen for ICD symptoms in individuals with DA-treated endocrine conditions.

MATERIALS AND METHODS

A cross-sectional analysis was conducted on 132 patients with pituitary disorders treated with DAs (DA exposed), as well as 58 patients with pituitary disorders and no history of DA exposure (non-DA exposed). Participants responded to the full version of the Questionnaire for Impulsive-Compulsive Disorders in Parkinson's disease (QUIP).

RESULTS

Compared with the non-DA-exposed group, a higher prevalence of DA-exposed patients tested positive for symptoms of any ICD or related behavior (52% vs. 31%, p < 0.01), any ICD (46% vs. 24%, p < 0.01), any related behavior (31% vs. 17%, p < 0.05), compulsive sexual behavior (27% vs. 14%, p < 0.04), and punding (20% vs. 7%, p < 0.02) by QUIP. On univariate analysis, DA treatment was associated with a two- to threefold increased risk of any ICD or related behavior [odds ratio (OR) 2.43] and any ICD (OR 2.70). In a multivariate analysis, independent risk factors for any ICD or related behavior were DA use (adjusted OR 2.22) and age (adjusted OR 6.76). Male gender was predictive of the risk of hypersexuality (adjusted OR 3.82).

DISCUSSION

Despite the QUIP limitations, a clear sign of increased risk of ICDs emerges in individuals with DA-treated pituitary disorders. Our data contribute to the growing evidence of DA-induced ICDs in endocrine conditions.

Prevalence of and Factors Associated with Dietary Supplement Use in a Stratified, Random Sample of US Military Personnel: The US Military Dietary Supplement Use Study

BACKGROUND

About 50% of Americans and 70% of US military service members use dietary supplements (DSs).

OBJECTIVES

This cross-sectional survey examined current prevalence of and factors associated with DS use in service members.

METHODS

A stratified random sample of 200,000 service members from the Air Force, Army, Marine Corps, and Navy was obtained from military manpower records, and these service members were asked to complete a questionnaire on their DS use and personal characteristics. Chi-square statistics and multivariable logistic regression examined differences across various strata of demographic, lifestyle, and military characteristics.

RESULTS

About 18% of successfully contacted service members (n = 26,681) completed the questionnaire between December 2018 and August 2019 (mean ± SD age: 33 ± 8 y, 86% male). Overall, 74% reported using ≥1 DS/wk. Multivitamins/multiminerals were the most commonly used DSs (45%), followed by combination products (44%), proteins/amino acids (42%), individual vitamins/minerals (31%), herbals (20%), joint health products (9%), and purported prohormones (5%). In multivariable analysis, factors independently associated with DS use included female gender [OR (female/male): 1.91; 95% CI: 1.73, 2.11], older age [OR (≥40/18-24 y): 1.25; 95% CI: 1.08, 1.44], higher education level [OR (college degree/high school or less): 1.35; 95% CI: 1.19, 1.53], higher BMI [OR (≥30/<25 kg/m2): 1.37; 95% CI: 1.25, 1.52], more weekly resistance training [OR (>300/≤45 min/wk): 5.05; 95% CI: 4.55, 5.61], smokeless tobacco use [OR (user/nonuser): 1.30; 95% CI: 1.17, 1.44], higher alcohol intake [OR (≥72/0 mL/wk): 1.41; 95% CI: 1.29, 1.54], and higher military rank [OR (senior officer/junior enlisted): 1.26; 95% CI: 1.06, 1.51].

CONCLUSIONS

Compared with civilian data from the NHANES, service members were much more likely to use DSs and used different types of DSs, especially combination products and proteins/amino acids often used to purportedly enhance physical performance. Comparisons with previous military data suggest DS use has increased over time.

Associations between eating disorders and illicit drug use among college students

OBJECTIVE

To estimate the associations between a positive eating disorder screen and any lifetime eating disorder diagnosis and illicit drug use among a large, diverse sample of college students.

METHOD

We analyzed data from the national (United States), cross-sectional 2018-2019 Healthy Minds Study (HMS; n = 42,618; response rate: 16%). HMS collects information on the physical, mental, and social health of college students. Multiple logistic regression analyses were used to estimate the association between a positive eating disorder screen (measured using the SCOFF) and any self-reported lifetime eating disorder diagnosis and self-reported illicit drug use in the past 30 days (any illicit drug use and use of marijuana, cocaine, heroin, methamphetamines, stimulants, ecstasy, opioids, benzodiazepines), while adjusting for potential confounders.

RESULTS

Among the sample, 54.34% (n = 28,608) were female and the mean age of participants was 23.30 (SE ± 0.05) years. Logistic regression analyses revealed unique associations between a positive eating disorder screen and any lifetime eating disorder diagnosis and illicit drug use among the sample of college student participants. A positive eating disorder screen was most strongly associated with methamphetamine use (adjusted odds ratio [AOR] 3.93, 95% confidence interval [CI] 1.43-10.78), and any lifetime eating disorder diagnosis was most strongly associated with benzodiazepine use (AOR 3.42, 95% CI 2.28-5.13).

DISCUSSION

Illicit drug use is common among college students who screen positive for an eating disorder and report any lifetime eating disorder diagnosis. The co-occurring nature of eating disorders and illicit drug use may complicate treatment and lead to compounded adverse health outcomes.

White matter deficits in cocaine use disorder: convergent evidence from in vivo diffusion tensor imaging and ex vivo proteomic analysis

White matter (WM) abnormalities in patients with cocaine use disorder (CUD) have been studied; however, the reported effects on the human brain are heterogenous and most results have been obtained from male participants. In addition, biological data supporting the imaging findings and revealing possible mechanisms underlying the neurotoxic effects of chronic cocaine use (CU) on WM are largely restricted to animal studies. To evaluate the neurotoxic effects of CU in the WM, we performed an in vivo diffusion tensor imaging assessment of male and female cocaine users (n = 75) and healthy controls (HC) (n = 58). Moreover, we performed an ex vivo large-scale proteomic analysis using liquid chromatography-tandem mass spectrometry in postmortem brains of patients with CUD (n = 8) and HC (n = 12). Compared with the HC, the CUD group showed significant reductions in global fractional anisotropy (FA) (p < 0.001), and an increase in global mean (MD) and radial diffusion (RD) (both p < 0.001). The results revealed that FA, RD, and MD alterations in the CUD group were widespread along the major WM tracts, after analysis using the tract-based special statistics approach. Global FA was negatively associated with years of CU (p = 0.0421) and female sex (p < 0.001), but not with years of alcohol or nicotine use. Concerning the fibers connecting the left to the right prefrontal cortex, Brodmann area 9 (BA9), the CUD group presented lower FA (p = 0.006) and higher RD (p < 0.001) values compared with the HC group. A negative association between the duration of CU in life and FA values in this tract was also observed (p = 0.019). Proteomics analyses in BA9 found 11 proteins differentially expressed between cocaine users and controls. Among these, were proteins related to myelination and neuroinflammation. In summary, we demonstrate convergent evidence from in vivo diffusion tensor imaging and ex vivo proteomics analysis of WM disruption in CUD.

Gender-specific approach in psychiatric diseases: Because sex matters

In both animals and human beings, males and females differ in their genetic background and hormonally driven behaviour and show sex-related differences in brain activity and response to internal and external stimuli. Gender-specific medicine has been a neglected dimension of medicine for long time, and only in the last three decades it is receiving the due scientific and clinical attention. Research has recently begun to identify factors that could provide a neurobiological basis for gender-based differences in health and disease and to point to gonadal hormones as important determinants of male-female differences. Animal studies have been of great help in understanding factors contributing to sex-dependent differences and sex hormones action. Here we review and discuss evidence provided by clinical and animal studies in the last two decades showing gender (in humans) and sex (in animals) differences in selected psychiatric disorders, namely eating disorders (anorexia nervosa, bulimia nervosa, binge eating disorder), schizophrenia, mood disorders (anxiety, depression, obsessive-compulsive disorder) and neurodevelopmental disorders (autism spectrum disorders, attention-deficit/hyperactivity disorder).

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.'

Patients with acromegaly might not be at higher risk for dopamine agonist-induced impulse control disorders than those with prolactinomas

OBJECTIVE

To evaluate the prevalence of impulse control disorders (ICD) and psychiatric symptoms in patients with acromegaly receiving dopamine agonists (DA) in comparison with those with prolactinoma, nonfunctioning pituitary adenomas (NFA), and healthy controls (HC).

DESIGN

Forty patients with acromegaly, 40 with prolactinoma, 38 with NFA, and 32 HCs were included. All patients and controls were evaluated using the revised version of the Minnesota Impulsive Disorders Interview (MIDI-R), Symptom Check List (SCL-90-R) questionnaire, Barratt Impulsiveness Scale (BIS-11), Beck Depression Inventory (BDI), and Beck Anxiety Inventory (BAI).

RESULTS

We detected ICD associated with DAs in two patients with acromegaly (5%) and three patients (7.5%) with prolactinoma. All patients' symptoms resolved after discontinuation of the drug. While the mean DA dose was higher in patients with acromegaly than prolactinomas (p < 0.05), no difference was detected in terms of ICD prevalence between two groups (p > 0.05). SCL-90 depression and interpersonal sensitivity subscale positivity was higher in patients with NFA than HCs. Patients with prolactinoma had higher obsession and interpersonal sensitivity positivity and those with NFA had higher somatization, interpersonal sensitivity, and depression positivity as compared to patients with acromegaly (p < 0.05 for all).

CONCLUSIONS

Although DA dose was significantly higher in patients with acromegaly, there was no significant difference in the prevalence of DA-related ICD. The higher prevalence of positive screening in SCL-90 in patients with NFA in comparison to HCs supports the hypothesis that the presence of a pituitary adenoma per se might cause significant psychiatric symptoms.

Sex differences in impulsivity in adult rats are mediated by organizational actions of neonatal gonadal hormones and not by hormones acting at puberty or in adulthood

Males as compared to females display increased impulsivity and inefficient inhibitory control and are more frequently diagnosed with disorders characterized by impulsivity. We previously demonstrated male rats make more impulsive action responses (i.e. premature responding) than females on the 5-choice serial reaction time task (5-CSRTT). Furthermore, pre-pubertal male rats make more impulsive choice responses (i.e. choosing an immediate small reward over a delayed larger reward) than females on a delayed-based reward T-maze task. The goal of the current work was to determine if gonadal hormones impact sex differences in impulsivity in adult rats. In an initial experiment, male and female rats underwent sham surgeries or were gonadectomized either pre-pubertally or during adulthood and tested on the 5-CSRTT in adulthood. Males displayed more impulsive action responses than females regardless of hormone status. In a second experiment, females received testosterone or vehicle injections on postnatal days 1 and 2. Males received vehicle injections. All rats were gonadectomized prior to puberty and tested on the 5-CSRTT in adulthood. Females treated neonatally with testosterone and control males made more impulsive action responses than control females. In another set of experiments, manipulation of gonadal hormones led to no differences in performance on the delayed-based reward T-maze task in males and females. Results indicate that no sex difference is apparent in impulsive choice on a delayed-base reward task in adult rats. They also reveal that adult sex differences on a task of impulsive action is mediated by organizational effects of gonadal hormones acting during the neonatal period and not impacted by hormones acting during puberty or adulthood.

Obesogenic diet-associated C-reactive protein predicts reduced central dopamine and corticostriatal functional connectivity in female rhesus monkeys

Alterations in dopamine (DA) signaling and reductions in functional connectivity (FC; a measure of temporal correlations of activity between different brain regions) within dopaminergic reward pathways are implicated in the etiology of psychopathology and have been associated with increased concentrations of inflammatory markers, including C-reactive protein. Peripheral and central inflammatory cytokines that have been shown to disrupt DA signaling and corticostriatal FC are associated with C-reactive protein, an acute phase reactant that is used translationally as a marker of systemic inflammation. One factor that can significantly increase systemic inflammation to produce neuroadaptations in reward pathways is a diet that results in fat mass accumulation (e.g. obesogenic diet). The current study in female rhesus monkeys maintained in a standard laboratory chow (n = 18) or on obesogenic diet (n = 16) for 12-months tested the hypothesis that an obesogenic diet would alter central DA and homovanillic acid (HVA) concentrations, and be associated with increased CRP concentrations and decreased FC between corticostriatal regions at 12-months following dietary intervention. We specifically assessed FC between the nucleus accumbens (NAcc) and two sub-regions of the prefrontal cortex (PFC) previously associated with CRP concentrations, the ventromedial PFC (vmPFC) and the orbitofrontal cortex (OFC), which are also involved in emotional and motivational salience assessment, and in goal-directed behavior, impulse control and the salience/value of food, respectively. Results showed that CSF DA concentrations were decreased (p = 0.002), HVA:DA ratios were increased (p = 0.016), and body mass index was increased (p = 0.047) over the 12-months of consuming an obesogenic diet. At 12-months, females maintained in the obesogenic diet exhibited higher CRP concentrations than females consuming chow-only (p = 0.008). Linear regression analyses revealed significant CRP by dietary condition interactions on DA concentrations (β = -5.10; p = 0.017) and HVA:DA ratios (β = 5.14; p = 0.029). Higher CRP concentrations were associated with lower CSF DA concentrations (r = -0.69; p = 0.004) and greater HVA:DA ratios only in females maintained in the obesogenic dietary condition (r = 0.58; p = 0.024). Resting-state magnetic resonance neuroimaging (rs-fMRI) in a subset of females from each diet condition (n = 8) at 12-months showed that higher CRP concentrations were associated decreased FC between the NAcc and subregions of the prefrontal cortex (PFC; p's < 0.05). Decreased FC between the NAcc and PFC subregions were also associated with lower concentrations of DA and greater HVA:DA ratios (p's < 0.05). Overall, these data suggest that increased inflammatory signaling driving heightened CRP levels may mediate the adverse consequences of obesogenic diets on DA neurochemistry and corticostriatal connectivity.

Crosstalk Between Kappa Opioid and Dopamine Systems in Compulsive Behaviors

The strength of goal-oriented behaviors is regulated by midbrain dopamine neurons. Dysfunctions of dopaminergic circuits are observed in drug addiction and obsessive-compulsive disorder. Compulsive behavior is a feature that both disorders share, which is associated to a heightened dopamine neurotransmission. The activity of midbrain dopamine neurons is principally regulated by the homeostatic action of dopamine through D2 receptors (D2R) that decrease the firing of neurons as well as dopamine synthesis and release. Dopamine transmission is also regulated by heterologous neurotransmitter systems such as the kappa opioid system, among others. Much of our current knowledge of the kappa opioid system and its influence on dopamine transmission comes from preclinical animal models of brain diseases. In 1988, using cerebral microdialysis, it was shown that the acute activation of the Kappa Opioid Receptors (KOR) decreases synaptic levels of dopamine in the striatum. This inhibitory effect of KOR opposes to the facilitating influence of drugs of abuse on dopamine release, leading to the proposition of the use of KOR agonists as pharmacological therapy for compulsive drug intake. Surprisingly, 30 years later, KOR antagonists are instead proposed to treat drug addiction. What may have happened during these years that generated this drastic change of paradigm? The collected evidence suggested that the effect of KOR on synaptic dopamine levels is complex, depending on the frequency of KOR activation and timing with other incoming stimuli to dopamine neurons, as well as sex and species differences. Conversely to its acute effect, chronic KOR activation seems to facilitate dopamine neurotransmission and dopamine-mediated behaviors. The opposing actions exerted by acute versus chronic KOR activation have been associated with an initial aversive and a delayed rewarding effect, during the exposure to drugs of abuse. Compulsive behaviors induced by repeated activation of D2R are also potentiated by the sustained co-activation of KOR, which correlates with decreased synaptic levels of dopamine and sensitized D2R. Thus, the time-dependent activation of KOR impacts directly on dopamine levels affecting the tuning of motivated behaviors. This review analyzes the contribution of the kappa opioid system to the dopaminergic correlates of compulsive behaviors.

Associations of Personality Traits and Emotional Intelligence: Comparing Individuals in Rehabilitation from Drug Misuse, Occasional Users and Non-Users

Background: Personality traits and Emotional Intelligence abilities have gained a central place in the etiology of drug use, although understudied until recently. Objective: To examine the associations between personality traits and Emotional Intelligence in people that are in process of rehabilitation from drug misuse, to compare them with occasional users and non-users and to estimate the factors associated with the likelihood of drug misuse. Methods: 244 individuals (52.5% male) participated in the study. Sixty of them were suffering from drug misuse disorders, thirty-two were individuals that used drugs occasionally and 142 were non-users. Personality was assessed with the EPQ and Emotional Intelligence with the WEILS. Results: Results suggested that in drug misuse, emotional use and regulation are positively correlated with extraversion, and negatively correlated with neuroticism, whilst people that misuse drugs differ from occasional and non-users in emotional use and regulation, and in all personality traits except extraversion. Regression analyses proposed that a combination of sex, age, emotional regulation, and neuroticism contributes to the likelihood of a person abusing drugs, as opposed to occasional or no use. Conclusion: Our findings showcase that Emotional Intelligence and personality traits indeed play an important role in drug use, specifically when considering factors that protect from or drive towards misuse. Such results call for the implementation of preventive programs for occasional drug users and therapeutic interventions for people that misuse drugs, targeting the levels of neuroticism and enhancing the ability of regulating the negative emotions, to protect from drug misuse.

Effects of early life stress on cocaine self-administration in post-pubertal male and female rhesus macaques

RATIONALE

Early life stress (ELS), including childhood maltreatment, is a predictive factor for the emergence of cocaine use disorders (CUDs) in adolescence.

OBJECTIVE

Accordingly, we examined whether post-pubertal male and female rhesus macaques that experienced infant maltreatment (maltreated, n = 7) showed greater vulnerability to cocaine self-administration in comparison with controls (controls, n = 7).

METHODS

Infant emotional reactivity was measured to assess differences in behavioral distress between maltreated and control animals as a result of early life caregiving. Animals were then surgically implanted with indwelling intravenous catheters and trained to self-administer cocaine (0.001-0.3 mg/kg/infusion) under fixed-ratio schedules of reinforcement. Days to acquisition, and sensitivity to (measured by the ED_Max dose of cocaine) and magnitude (measured by response rates) of the reinforcing effects of cocaine were examined in both groups.

RESULTS

Maltreated animals demonstrated significantly higher rates of distress (e.g., screams) in comparison with control animals. When given access to cocaine, control males required significantly more days to progress through terminal performance criteria compared with females and acquired cocaine self-administration slower than the other three experimental groups. The dose that resulted in peak response rates did not differ between groups or sex. Under 5-week, limited-access conditions, males from both groups had significantly higher rates of responding compared with females.

CONCLUSIONS

In control monkeys, these data support sex differences in cocaine self-administration, with females being more sensitive than males. These findings also suggest that ELS may confer enhanced sensitivity to the reinforcing effects of cocaine, especially in males.

Altered topological connectivity of internet addiction in resting-state EEG through network analysis

The results of some neuroimaging studies have revealed that people with internet addiction (IA) exhibit structural and functional changes in specific brain areas and connections. However, the understanding about global topological organization of IA may also require a more integrative and holistic view of brain function. In the present study, we used synchronization likelihood combined with graph theory analysis to investigate the functional connectivity (FC) and topological differences between 25 participants with IA and 27 healthy controls (HCs) based on their spontaneous EEG activities in the eye-closed resting state. There were no significant differences in FC (total network or sub-networks) between groups (p > .05 for all). Graph analysis showed significantly lower characteristic path length and clustering coefficient in the IA group than in the HC group in the beta and gamma bands, respectively. Altered nodal centralities of the frontal (FP₁, FPz) and parietal (CP₁, CP₅, PO₃, PO₇, P₅, P_6, TP₈) lobes in the IA group were also observed. Correlation analysis demonstrated that the observed regional alterations were significantly correlated with the severity of IA. Collectively, our findings showed that IA group demonstrated altered topological organization, shifting towards a more random state. Moreover, this study revealed the important role of altered brain areas in the neuropathological mechanism of IA and provided further supportive evidence for the diagnosis of IA.

Prenatal testosterone exposure is associated with delay of gratification and attention problems/overactive behavior in 3-year-old boys

Sex differences in self-control become apparent during preschool years. Girls are better able to delay their gratification and show less attention problems and overactive behavior than boys. In this context, organizational effects of gonadal steroids affecting the neural circuitry underlying self-control could be responsible for these early sex differences. In the present study testosterone levels measured in amniotic fluid (via ultra performance liquid chromatography and tandem mass spectrometry) were used to examine the role of organizational sex hormones on self-control. One hundred and twenty-two 40-month-old children participated in a delay of gratification task (DoG task) and their parents reported on their attention problems and overactive behavior. Girls waited significantly longer for their preferred reward than boys, and significantly more girls than boys waited the maximum period of time, providing evidence for sex differences in delay of gratification. Boys that were rated as suffering from more attention problems and overactive behavior waited significantly shorter in the DoG task. Amniotic testosterone measures were reliable in boys only. Most importantly, boys who waited shorter in the DoG task and boys who were reported to suffer from more attention problems and overactive behavior had higher prenatal testosterone levels. These findings extend our knowledge concerning organizational effects of testosterone on the brain circuitry underlying self-control in boys, and are of relevance for understanding how sex differences in behavioral disorders are connected with a lack of self-control.

Impulse control disorders in patients with prolactinoma receiving dopamine agonist therapy: a prospective study with 1 year follow-up

OBJECTIVE

To assess prospectively the prevalence of impulse control disorders (ICD), psychiatric symptoms, and their clinical correlates in patients with prolactinoma receiving dopamine agonists (DA) in comparison to those with non-functioning pituitary adenomas (NFA) and healthy controls (HC).

METHODS

A total of 25 patients with prolactinoma, 31 with NFA, and 32 HCs were included in the study. All patients and controls were screened for the presence of ICDs and other psychiatric disorders using revised version of Minnesota Impulsive Disorders Interview (MIDI-R), Barratt Impulsiveness Scale (BIS-11), Symptom Check List (SCL-90-R) questionnaire and Beck Depression Inventory (BDI), and Beck Anxiety Inventory (BAI).

RESULTS

We detected two new cases (8%) of ICD associated with DAs. Both cases presented with hypersexuality, which reversed totally or decreased upon discontinuation of the drug. The re-challenge of the DA in a smaller dose has led to either no symptoms or weaker symptoms than before. There was an increase in the number of patients who screened positive on obsession, interpersonal sensitivity, paranoid ideation, and additional items subscales of SCL-90-R in comparison to HCs at the end of the study period (p < 0.05 for all). Likewise, cumulative DA dose was positively correlated to obsession, interpersonal sensitivity, paranoid ideation, hostility, phobic anxiety subscales, and GSI scores of SCL-90-R (p < 0.05 for all).

CONCLUSIONS

DAs are associated with a small but substantial short-term risk of ICD development and a broad range of psychiatric symptoms in patients with prolactinoma receiving DAs.

Sex and Feeding Status Differently Affect Natural Reward Seeking Behavior in Olfactory Bulbectomized Rats

Substance abuse and depression are common psychiatric disorders with a high rate of comorbidity. Both conditions affect differently men and women and preclinical research has showed many sex differences in drug addiction and depression. The most common approach for modeling depression-addiction comorbidity is the combination of the intravenous drug self-administration and the olfactory bulbectomy (OBX) models in rats. Such a combination has revealed enhanced drug-taking and drug-seeking behaviors in OBX rats, but no study has investigated so far potential sex differences in operant responding and motivation for natural reinforcers in OBX rats. This study investigated for the first time operant self-administration of palatable food pellets in male and female OBX rats under different feeding status, i.e., ad libitum vs. restricted food, and schedules of reinforcement, i.e., a continuous ratio schedule fixed ratio 1 (FR1) vs. a complex (FR5_(x)) second order schedule of reinforcement. In the FR1 experiment, OBX rats of both sexes exhibited lower operant responding and intake of palatable food pellets than sham-operated controls, with food restriction leading to increased operant responding in both OBX and SHAM groups. Female rats showed higher responding than males but this effect was abolished by the OBX lesion. Similarly, in the (FR5_(x)) second order schedule of reinforcement both male and female OBX rats showed lower responding and food intake, with SHAM and OBX females showing higher operant responding than corresponding male groups. Overall, our findings showed that: (i) responding for food was lower in OBX than in SHAM rats under both FR1 and (FR5_(x)) schedules of reinforcement; (ii) sex and food restriction affect operant responding for palatable food; and (iii) the suppressing effect of OBX lesion on food intake was consistently present in both sexes and represents the most robust factor in the analysis. This may represent anhedonia which is associated with depressive-like phenotype and palatable food self-administration may serve as a robust behavioral index of anhedonia in the OBX model.

Sex-specific attenuation of impulsive action by progesterone in a go/no-go task for cocaine in rats

RATIONALE

Previous work indicated that progesterone (PRO) reduced impulsive choice for cocaine in female but not male rats (Smethells et al. Psychopharmacology 233:2999-3008, 2016). Impulsive action, typically measured by responding for a reinforcer during a signaled period of nonavailability of natural reinforcers, predicts initiation and escalation of drug use in animals and humans. The present study examined impulsive action for cocaine using PRO in male and female rats trained on a go/no-go task.

OBJECTIVE

Rats were trained on a go/no-go task to respond for cocaine infusions (0.4 mg/kg/inf). During the "go" component, responding was reinforced on a VI 30-s schedule, whereas during the "no-go" component, withholding a response was reinforced on a differential reinforcement of other behavior (DRO) 30-s schedule. A response during the no-go component resets the DRO timer and served as a measure of impulsive action. After baseline responding was established, rats were pretreated with vehicle (VEH) or PRO (0.5 mg/kg), and DRO resets and responding during the go component for cocaine were compared in males vs. females.

RESULTS

DRO resets were significantly lower following PRO treatment compared to VEH in female, but not male, rats. Response rates and overall infusions during the go component were not significantly altered by PRO in either females or males.

CONCLUSION

Treatment with PRO resulted in a sex-specific reduction in impulsive action for cocaine, while not affecting cocaine self-administration.

Sex as a biological variable: Drug use and abuse

The study of sex as a biological variable is a necessary emphasis across a wide array of endpoints, including basic neuroscience, medicine, mental health, physiology and behavior. The present review summarizes work from clinical and preclinical populations on sex differences in drug use and abuse, ranging from initiation to escalation/dysregulation and from drug cessation/abstinence to relapse. These differences are analyzed in the context of the addiction cycle conceptualization of Koob and his colleagues and address patterns of drug use (binge/intoxication), motivation underlying its use (withdrawal/negative affect) and likelihood and causes of craving and relapse of drug taking (preoccupation/anticipation). Following this overview, an assessment of the basis for the reported sex differences is discussed in the context of the affective (rewarding and aversive) properties of drugs of abuse and how such properties and their balance vary with sex and contribute to drug intake. Finally, the interaction of sex with several experiential (drug history) and subject (age) factors and how these interactions affect reward and aversion are discussed to highlight the importance of understanding such interactions in predicting drug use and abuse. We note that sex as a biological variable remains one of critical evaluation and that such investigations of sex differences in drug use and abuse continue and be expanded to assess all facets of their mediation, including these affective properties, how their balance may be impacted by the multiple conditions under which drugs are taken and how this overall balance affects drug use and addiction vulnerability.

Epigenetics: a link between addiction and social environment

The detrimental effects of drug abuse are apparently not limited to individuals but may also impact the vulnerability of their progenies to develop addictive behaviours. Epigenetic signatures, early life experience and environmental factors, converge to influence gene expression patterns in addiction phenotypes and consequently may serve as mediators of behavioural trait transmission between generations. The majority of studies investigating the role of epigenetics in addiction do not consider the influence of social interactions. This shortcoming in current experimental approaches necessitates developing social models that reflect the addictive behaviour in a free-living social environment. Furthermore, this review also reports on the advancement of interventions for drug addiction and takes into account the emerging roles of histone deacetylase (HDAC) inhibitors in the etiology of drug addiction and that HDAC may be a potential therapeutic target at nucleosomal level to improve treatment outcomes.

The impact of cognitive training in substance use disorder: the effect of working memory training on impulse control in methamphetamine users

OBJECTIVES

Impulsivity is a vulnerability trait for poor self-regulation in substance use disorder (SUD). Working memory (WM) training improves impulsivity and self-regulation in psychiatric disorders. Here we test WM training in methamphetamine use disorder (MUD).

METHODS

There are 15 MUD patients receiving inpatient treatment as usual (TAU) and 20 who additionally completed WM cognitive training (CT) and 25 healthy controls (HC). MANCOVA repeated measures analyses examined changes in impulsivity and self-regulation at baseline and after 4 weeks.

RESULTS

Post hoc t tests confirmed that at baseline, feelings of self-control were significantly lower in the MUD (t = 2.001, p = 0.05) and depression was higher (t = 4.980, p = 0.001), as was BIS total impulsivity (t = 5.370, p = 0.001) compared to the HC group. Total self-regulation score was higher in HC than MUD patients (t = 5.370, p = 0.001). CT had a 35% learning rate (R ² = 0.3523, p < 0.05). Compared to follow-up TAU, follow-up CT group had higher self-reported mood scores (t = 2.784, p = 0.01) and higher compared to CT baseline (t = 2.386, p = 0.036). Feelings of self-control were higher in CT than TAU at follow-up (t = 2.736, p = 0.012) and also compared to CT baseline (t = 3.390, p = 0.006), lack of planning significantly improved in CT between baseline and follow-up (t = 2.219, p = 0.048), as did total impulsivity scores (t = 2.085, p = 0.048). Measures of self-regulation were improved in the CT group compared to TAU at follow-up, in total score (t = 2.442, p = 0.038), receiving score (t = 2.314, p = 0.029) and searching score (t = 2.362, p = 0.027). Implementing self-regulation was higher in the CT group compared to TAU (t = 2.373, p = 0.026).

CONCLUSIONS

WM training may improve control of impulsivity and self-regulation in people with MUD.