Project description:Circadian rhythm disturbances have long been associated with the development of psychiatric disorders, including mood and substance use disorders. Adolescence is a particularly vulnerable time for the onset of psychiatric disorders and for circadian rhythm and sleep disruptions. Preclinical studies have found that circadian rhythm disruption (CRD) impacts the brain and behavior, but this research is largely focused on adult disruptions. Here, we sought to determine the long-term behavioral and neurobiological effects of CRD during early adolescence by exposing mice to 12 h shifts in the light/dark cycle. We hypothesized that adolescent CRD would have a greater effect on psychiatric-related behaviors, relative to adult disruption. To identify possible mechanisms, we also measured gene expression in brain regions relevant to circadian rhythms, mood and reward. We found that disruption during early adolescence, but not adulthood, persistently increased exploratory drive (risk-taking behavior) and cocaine preference when tested later in life. Interestingly, we found sex differences when intravenous cocaine self-administration was tested. While female mice with a history of adolescent CRD had a greater propensity to self-administer cocaine, as well as increased motivation and cue-induced reinstatement, male adolescent CRD mice had reduced motivation and extinction responding. Overall, adolescent CRD in mice caused persistent increases in risky behavior, cocaine reward and cocaine self-administration, which suggests that CRD during adolescence may predispose individuals towards substance use disorders. Importantly, we found that many transcripts were affected by adolescent CRD and these were largely distinct across sex and brain region. Future research is required to elucidate how adolescent CRD affects behaviors relevant to mood- and substance use-related disorders across the 24-hour day, as well as to identify intervention strategies to alleviate disruption during adolescence and novel therapeutic approaches once symptoms have begun.
Project description:Frequent shift work causes disruption of the circadian rhythm and might on the long-term result in increased health risk. Current biomarkers evaluating the presence of circadian rhythm disturbance (CRD) require 24-hr (around the clock) measurements, which is not practical for use in large-scale (human) studies. The aim of the present study was to identify universal biomarkers for CRD independent of time of day using a transcriptomics approach. Female FVB mice were exposed to six shifts in a clockwise (CW) and counterclockwise (CCW) CRD protocol and sacrificed at baseline and after 1 shift, 6 shifts, 5 days recovery and 14 days recovery, respectively. At six time-points during the day, livers were collected for mRNA microarray analysis. Bioinformatics analysis identified a set of universal markers for CRD. These biomarkers might be useful to measure CRD and can be used later on for monitoring the effectiveness of intervention strategies aiming to prevent or minimize chronic adverse health effects.
Project description:Heightened risk-taking tendencies during adolescence have been hypothesized to be attributable to physiological differences of maturation in key brain regions. The socioemotional system (e.g., nucleus accumbens), which is instrumental in reward response, shows a relatively earlier development trajectory than the cognitive control system (e.g., medial prefrontal cortex), which regulates impulse response. This developmental imbalance between heightened reward seeking and immature cognitive control potentially makes adolescents more susceptible to engaging in risky activities. Here, we assess brain structure in the socioemotional and cognitive control systems through viscoelastic stiffness measured with magnetic resonance elastography (MRE) and volumetry, as well as risk-taking tendencies measured using two experimental tasks in 40 adolescents (mean age = 13.4 years old). MRE measures of regional brain stiffness reflect brain health and development via myelin content and glial matrix makeup, and have been shown to be highly sensitive to cognitive processes as compared to measures of regional brain volume and diffusion weighted imaging metrics. We find here that the viscoelastic and volumetric differences between the nucleus accumbens and the prefrontal cortex are correlated with increased risk-taking behavior in adolescents. These differences in development between the two brain systems can be used as an indicator of those adolescents who are more prone to real world risky activities and a useful measure for characterizing response to intervention.
Project description:Nuclear receptor subfamily 1, group D, member 1 (Nr1d1) (also known as Rev-erb alpha) has been linked to circadian rhythm regulation, mood-related behavior, and disorders associated with social deficits. Recent work from our laboratory found striking decreases in Nr1d1 in nucleus accumbens (NAc) in the maternal condition and indirect evidence that Nr1d1 was interacting with numerous addiction and reward-related genes to modulate social reward. In this study, we applied our insights from the maternal state to non-parental adult mice to determine whether decreases in Nr1d1 expression in NAc via adeno-associated viral (AAV) vectors and short hairpin RNA (shRNA)-mediated gene knockdown were sufficient to modulate social reward and mood-related behaviors. We also used microarray analysis of to identify gene expression alterations induced by the lowering of Nr1d1 expression. We used microarrays to evalute the effects of knockdown of mRNA for Nr1d1 in nuclues accumbens on gene expression.
Project description:Adolescence is a sensitive window for reward- and stress-associated behavior. Although stress during this period causes long-term changes in behavior in males, how females respond is relatively unknown. Here we show that social isolation stress in adolescence, but not adulthood, induces persistent but opposite effects on anxiety- and cocaine-related behaviors in male vs. female mice, and that these effects are reflected in transcriptional profiles within the adult medial amygdala (meA). By integrating differential gene expression with co-expression network analyses, we identified crystallin mu (Crym), a thyroid hormone binding protein, as a key driver of these transcriptional profiles. Manipulation of Crym specifically within adult meA neurons recapitulates the behavioral and transcriptional effects of social isolation and re-opens a window of plasticity that is otherwise closed. Our results establish that meA is essential for sex-specific responses to stressful and rewarding stimuli through transcriptional programming that occurs during adolescence.
Project description:Whilst reward pathologies e.g., anhedonia and apathy, are major and common in stress-related neuropsychiatric disorders, their neurobiological bases and therefore treatment are poorly understood. Functional imaging studies in humans with reward pathology indicate that attenuated BOLD activity in nucleus accumbens (NAc) occurs during reward anticipation/expectancy but not reinforcement; potentially, this is dopamine (DA) related. In mice, chronic social stress (CSS) leads to reduced reward learning and effortful motivation and, here, DA-sensor fibre photometry was used to investigate whether these behavioural deficits co-occur with altered NAc DA activity during reward anticipation and/or reinforcement. In CSS mice relative to controls: (1) Reduced discriminative learning of the sequence, tone-on + appetitive behaviour = tone-on + sucrose reinforcement, co-occurred with attenuated NAc DA activity throughout tone-on and sucrose reinforcement. (2) Reduced effortful motivation during the sequence, operant behaviour = tone-on + sucrose delivery + tone-off / appetitive behaviour = sucrose reinforcement, co-occurred with attenuated NAc DA activity at tone-on and typical activity at sucrose reinforcement. (3) Reduced effortful motivation during the sequence, operant behaviour = appetitive behaviour + sociosexual reinforcement co-occurred with typical NAc DA activity at female reinforcement. Therefore, in CSS mice attenuated NAc DA activity is specific to reward anticipation and as such potentially causal to deficits in learning and motivation. CSS did not impact on the transcriptome of ventral tegmentum DA neurons, suggesting that its stimulus-specific effects on NAc DA activity originate elsewhere in the neural circuitry of reward processing.
Project description:The nucleus accumbens (NAc) plays an important role in motivation and reward processing. Recent studies suggest that different NAc subnuclei differentially contribute to reward-related behaviors. However, how reward is encoded in individual NAc neurons remains unclear. Using in vivo single-cell resolution calcium imaging, we discovered diverse patterns of reward encoding in the medial and lateral shell subdivision of the NAc (NAcMed and NAcLat, respectively). Reward consumption increases NAcLat activity but decreases NAcMed activity, albeit with high variability among neurons. The heterogeneity in reward encoding could be attributed to differences in their synaptic inputs and transcriptional profiles. Specific optogenetic activation of Nts-positive neurons in the NAcLat promotes positive reinforcement, while activation of Cartpt-positive neurons in the NAcMed induces behaviour aversion. Collectively, our study reveals organizational and transcriptional differences in NAc subregions, and provides a framework for future dissection of NAc subregions in physiological and pathological conditions.