Vulnerability for cocaine dependence / Involvement of µ-opioid receptors

Drug dependence is a major health issue worldwide, which is characterised by its persistence and high rates of relapse. Individual differences exist in the vulnerability for drug dependence after first exposure to drugs of abuse like cocaine. A likely risk factor for drug dependence is the sensitivity to the positive reinforcing effects of drugs of abuse. The studies described in this thesis reveal an important role of µ-opioid receptors in the sensitivity to cocaine reinforcement. Knockout mice, that lack the gene encoding the µ-opioid receptor, were impaired in cocaine self-administration, suggesting that they are less sensitive to the reinforcing effects of cocaine. In contrast, both acute and chronic cocaine-induced locomotor activity were not subjective to changes in absence of µ-opioid receptors. Therefore, µ-opioid receptors appear to have an important and specific role in modulating cocaine reinforcement. Further studies described in this thesis provide insight into the mechanism of µ-opioid receptor mediated modulation of cocaine reinforcement. Cocaine self-administration was associated with pro-opiomelanocortin (POMC) expression in the arcuate nucleus, suggesting that POMC and POMC-derived peptides, like the µ-opioid receptor selective peptide â-endorphin, might contribute to cocaine reinforcement. In absence of µ-opioid receptors, increased GABAergic inhibitory input onto dopamine neurons in the ventral tegmental area was observed. It is proposed that regulation of GABAergic neurotransmission in the VTA contributes to µ-opioid receptor mediated modulation of cocaine reinforcement. Considering the important role of µ-opioid receptors in cocaine reinforcement, variations in µ- opioid receptors might contribute to vulnerability for cocaine dependence. Future studies, both preclinical and clinical, should confirm that variations in µ-opioid receptors indeed contribute to the risk for cocaine dependence. This knowledge may lead to improved strategies in prevention and treatment of drug dependence

Alcohol cue reactivity in the brain:Age-related differences in the role of social processes in addiction in male drinkers

Social attunement (SA)-the tendency to harmonize behavior with the social environment-has been proposed to drive the escalation of alcohol use in adolescence, while reducing use in adulthood. Little is known about how heightened social sensitivity in adolescence may interact with neural alcohol cue reactivity-a marker of alcohol use disorder-and its relationship to alcohol use severity over time. The aims of this study were to test whether (1) adolescents and adults differ in social alcohol cue reactivity in the nucleus accumbens, anterior cingulate cortex, and right medial prefrontal cortex (mPFC), and (2) age moderates the relationship between social alcohol cue reactivity and social attunement, measures of drinking at baseline, and changes in drinking over time. A sample of male adolescents (16-18 years) and adults (29-35 years) completed an fMRI social alcohol cue-exposure task at baseline and an online follow-up two to three years later. No main effects of age or drinking measures were observed in social alcohol cue reactivity. However, age significantly moderated associations of social alcohol cue reactivity in the mPFC and additional regions from exploratory whole-brain analyses with SA, with a positive association in adolescents and negative association in adults. Significant age interactions emerged only for SA in predicting drinking over time. Adolescents with higher SA scores escalated drinking, while adults with higher SA scores reduced drinking. These findings warrant further research on SA as a risk and protective factor and suggest that social processes influence cue reactivity differentially in male adolescents and adults.</p

Individual Differences in Social Play Behaviour Predict Alcohol Intake and Control Over Alcohol Seeking in Rats

Rationale Social play behaviour is a rewarding social activity displayed by young mammals, thought to be important for the development of brain and behaviour. Indeed, disruptions of social play behaviour in rodents have been associated with cognitive deficits and augmented sensitivity to self-administration of substances of abuse, including alcohol, later in life. However, the relation between social development and loss of control over substance use, a key characteristic of substance use disorders including alcohol use disorder (AUD), has not been investigated. Moreover, it remains unknown how inherent differences in playfulness relate to differences in the sensitivity to substance use and AUD. Objective The objective of this study is to determine how individual differences in juvenile social play behaviour predict alcohol intake and loss of control over alcohol seeking. Methods Juvenile male Lister hooded rats were characterized for their tendency to engage in social play behaviour. Subsequently, alcohol consumption and conditioned suppression of alcohol seeking were assessed in the tertiles of rats that showed the most and least social play. Results The rats that engaged most in social play behaviour consumed more alcohol than their less playful counterparts. However, whereas the most playful rats showed intact conditioned suppression of alcohol seeking, the least playful rats showed no such suppression. Conclusion Individual levels of playfulness predict the sensitivity to alcohol-directed behaviour. Highly playful rats are more prone to alcohol intake, yet show greater control over alcohol seeking. These findings increase our understanding of the relationship between social development and vulnerability to AUD

Genetics and epigenetics: paternal adolescent ethanol consumption in serotonin transporter knock-out rats and offspring sensitivity to ethanol

RATIONALE: Alcohol use disorder (AUD) is shown to have an overall heritability of around 50%. One of the genes associated with AUD is SLC6A4 (solute carrier family 6 member A4) which codes for the serotonin transporter (SERT). The study looked at serotonin dysfunction on ethanol consumption in adolescents and the subsequent intergenerational effects of drinking by using a rat model: SERT+/+ (regular functioning), SERT+/- (50% transporter reduction) and SERT-/- (complete reduction). OBJECTIVES: We investigated sex and genotype differences in ethanol consumption in SERT knock-out Wistar rats (F0) followed by studying behaviour in the offspring (F1) of the male drinkers to assess effects of paternal alcohol consumption. METHODS: An intermittent access two-bottle choice paradigm (IA2BC) was used to yield ethanol drinking behaviour in F0 adolescent Wistar rats. The highest drinking males were mated to alcohol-naive females and their offspring were compared with controls. Drinking behaviour (IA2BC) and ethanol-induced motor coordination effects (via rotarod) were measured in the F1s. RESULTS: F0 drinking saw no SERT genotype differences in males. However, females consumed higher volumes of ethanol compared to males, with SERT-/- females showing the highest intake. A clearer genotype effect was seen in the F1 animals, with reduction in SERT activity leading to enhanced ethanol intake in both sexes. Importantly, paternal exposure to ethanol significantly reduced the ethanol induced motor side effects in offspring, independent of sex and genotype. CONCLUSIONS: These indicate a difference in the way genetic factors may act across sexes and suggest the involvement of epigenetic mechanisms in the intergenerational effects of alcohol

Alcohol cue reactivity in the brain: Age-related differences in the role of social processes in addiction in male drinkers

Social attunement (SA)-the tendency to harmonize behavior with the social environment-has been proposed to drive the escalation of alcohol use in adolescence, while reducing use in adulthood. Little is known about how heightened social sensitivity in adolescence may interact with neural alcohol cue reactivity-a marker of alcohol use disorder-and its relationship to alcohol use severity over time. The aims of this study were to test whether (1) adolescents and adults differ in social alcohol cue reactivity in the nucleus accumbens, anterior cingulate cortex, and right medial prefrontal cortex (mPFC), and (2) age moderates the relationship between social alcohol cue reactivity and social attunement, measures of drinking at baseline, and changes in drinking over time. A sample of male adolescents (16-18 years) and adults (29-35 years) completed an fMRI social alcohol cue-exposure task at baseline and an online follow-up two to three years later. No main effects of age or drinking measures were observed in social alcohol cue reactivity. However, age significantly moderated associations of social alcohol cue reactivity in the mPFC and additional regions from exploratory whole-brain analyses with SA, with a positive association in adolescents and negative association in adults. Significant age interactions emerged only for SA in predicting drinking over time. Adolescents with higher SA scores escalated drinking, while adults with higher SA scores reduced drinking. These findings warrant further research on SA as a risk and protective factor and suggest that social processes influence cue reactivity differentially in male adolescents and adults

Acquiring Financial Support for Children's Sports Participation: Co-Creating a Socially Safe Environment for Parents from Low-Income Families

Despite the many benefits of club-organized sports participation for children, sports participation is lower among children from low-income families than among those from middle- or high-income families. Social safety experienced by parents from low-income families is an important facilitator for parents to request financial support for their children's sports participation. Therefore, the first aim of this study was to better understand parental social (un)safety in the context of acquiring financial support for children's sports participation and how to create a safe social environment for low-income parents to request and receive this financial support. The second aim was to describe the co-creation process, which was organized to contribute to social safety solutions. To reach these goals, we applied a participatory action research method in the form of four co-creation sessions with professionals and an expert-by-experience, as well as a group interview with parents from low-income families. The data analysis included a thematic analysis of the qualitative data. The results showed that from the perspective of parents, social safety encompassed various aspects such as understandable information, procedures based on trust, and efficient referral processes. Sport clubs were identified as the primary source of information for parents. Regarding the co-creation process, the study found that stakeholders tended to overestimate parental social safety levels. Although the stakeholders enjoyed and learned from the sessions, differences in prior knowledge and a lack of a shared perspective on the purpose of the sessions made it challenging to collaboratively create solutions. The study's recommendations include strategies for increasing parental social safety and facilitating more effective co-creation processes. The findings of this study can be used to inform the development of interventions that contribute to a social environment in which parents from low-income families feel safe to request and receive financial support for their children's sports participation

Age-related differences in the effect of chronic alcohol on cognition and the brain: a systematic review

Adolescence is an important developmental period associated with increased risk for excessive alcohol use, but also high rates of recovery from alcohol use-related problems, suggesting potential resilience to long-term effects compared to adults. The aim of this systematic review is to evaluate the current evidence for a moderating role of age on the impact of chronic alcohol exposure on the brain and cognition. We searched Medline, PsycInfo, and Cochrane Library databases up to February 3, 2021. All human and animal studies that directly tested whether the relationship between chronic alcohol exposure and neurocognitive outcomes differs between adolescents and adults were included. Study characteristics and results of age-related analyses were extracted into reference tables and results were separately narratively synthesized for each cognitive and brain-related outcome. The evidence strength for age-related differences varies across outcomes. Human evidence is largely missing, but animal research provides limited but consistent evidence of heightened adolescent sensitivity to chronic alcohol's effects on several outcomes, including conditioned aversion, dopaminergic transmission in reward-related regions, neurodegeneration, and neurogenesis. At the same time, there is limited evidence for adolescent resilience to chronic alcohol-induced impairments in the domain of cognitive flexibility, warranting future studies investigating the potential mechanisms underlying adolescent risk and resilience to the effects of alcohol. The available evidence from mostly animal studies indicates adolescents are both more vulnerable and potentially more resilient to chronic alcohol effects on specific brain and cognitive outcomes. More human research directly comparing adolescents and adults is needed despite the methodological constraints. Parallel translational animal models can aid in the causal interpretation of observed effects. To improve their translational value, future animal studies should aim to use voluntary self-administration paradigms and incorporate individual differences and environmental context to better model human drinking behavior

Amygdala 14-3-3ζ as a Novel Modulator of Escalating Alcohol Intake in Mice

Alcoholism is a devastating brain disorder that affects millions of people worldwide. The development of alcoholism is caused by alcohol-induced maladaptive changes in neural circuits involved in emotions, motivation, and decision-making. Because of its involvement in these processes, the amygdala is thought to be a key neural structure involved in alcohol addiction. However, the molecular mechanisms that govern the development of alcoholism are incompletely understood. We have previously shown that in a limited access choice paradigm, C57BL/6J mice progressively escalate their alcohol intake and display important behavioral characteristic of alcohol addiction, in that they become insensitive to quinine-induced adulteration of alcohol. This study used the limited access choice paradigm to study gene expression changes in the amygdala during the escalation to high alcohol consumption in C57BL/6J mice. Microarray analysis revealed that changes in gene expression occurred predominantly after one week, i.e. during the initial escalation of alcohol intake. One gene that stood out from our analysis was the adapter protein 14-3-3ζ, which was up-regulated during the transition from low to high alcohol intake. Independent qPCR analysis confirmed the up-regulation of amygdala 14-3-3ζ during the escalation of alcohol intake. Subsequently, we found that local knockdown of 14-3-3ζ in the amygdala, using RNA interference, dramatically augmented alcohol intake. In addition, knockdown of amygdala 14-3-3ζ promoted the development of inflexible alcohol drinking, as apparent from insensitivity to quinine adulteration of alcohol. This study identifies amygdala 14-3-3ζ as a novel key modulator that is engaged during escalation of alcohol use

Psychosocial functioning in adolescents growing up with chronic disease: The Dutch HBSC study

Many adolescents worldwide (indirectly) grow up with a chronic disease, which may impact their functioning and wellbeing. The objective of this study is to assess whether adolescents with a (family member with a) chronic disease differ from their healthy counterparts in terms of psychosocial functioning. Data from the Dutch 2013 HBSC-survey were used, including 7168 adolescents (Meanage = 13.7, SD = 1.57, 50.5% female). Participants indicated whether they or one of their family members had a long-term (> 3 months) disease or disability (mental/physical) and were categorized into four groups based on disease presence (none, other, self, both). Psychosocial functioning was assessed in terms of life satisfaction, self-rated health, psychosomatic health, mental health problems, support, substance use, physical exercise, screen time, and school liking. Chronically diseased adolescents (n = 162) reported lower life satisfaction, self-rated and psychosomatic health, more mental health problems, lower peer support, more substance use, and less physical exercise compared to healthy peers. Chronically diseased adolescents who also had a family member with a chronic disease (n = 74) showed comparable outcomes on these life domains, although they did not differ from their healthy peers regarding peer support, substance use, and physical activity. Healthy adolescents with a chronically diseased family member (n = 737) reported significantly lower life satisfaction, self-rated and psychosomatic health, more mental health problems, and less family support compared to healthy peers who grew up in healthy families; however, they reported more positive outcomes than adolescents who had a chronic disease themselves. Conclusion: Having a (family member with a) chronic disease is associated with impaired psychosocial functioning on various life domains. Our findings aid in understanding the psychosocial associates of chronic disease and imply that caregivers should be observant of psychosocial problems among vulnerable adolescents to provide appropriate guidance.What is Known:• Adolescents who grow up with a (family member with a) chronic disease encounter numerous challenges that may be related to poorer developmental outcomes on the long term.What is New:• This study adds a comprehensive overview of the psychosocial functioning of adolescents with a (family member with a) chronic disease, as compared to healthy counterparts that grow up in a healthy family

A cross-sectional study on gaming intensity and social vulnerability in adolescents that have a chronic condition

BACKGROUND: Adolescents growing up with a chronic condition might experience more social vulnerabilities compared to their healthy peers as an indirect result of their conditions. This can lead to a relatedness need frustration for these adolescents. Consequently, they might spend more time playing video games compared to their peers. Research shows that both social vulnerability and gaming intensity are predictors for problematic gaming. Therefore, we investigated if social vulnerability and gaming intensity are more pronounced in adolescents that have a chronic condition compared to the general population; and if these levels reflect the levels of a clinical group being treated for Internet Gaming Disorder (IGD). METHODS: Data on peer problems and gaming intensity were compared from three separate samples: a national representative sample of adolescents, a clinical sample of adolescents that are undergoing treatment for IGD, and a sample of adolescents diagnosed with a chronic condition. RESULTS: No differences were found on either peer problems or gaming intensity between the group of adolescents that have chronic conditions and the national representative group. The group with chronic conditions scored significantly lower on gaming intensity than the clinical group. No significant differences were found between these groups on peer problems. We repeated the analyses for boys only. Similar results were found for the group with chronic conditions compared to the national representative group. The group with chronic conditions now scored significantly lower on both peer problems and gaming intensity than the clinical group. CONCLUSION: Adolescents growing up with a chronic condition appear similar in their gaming intensity and peer problems compared to their healthy peers