Effects of prenatal exposure to cocaine on brain structure and function

GABA system in the prefrontal cortex involved in psychostimulant addiction

Drug addiction is a chronic and relapse brain disorder. Psychostimulants such as cocaine and amphetamine are highly addictive drugs. Abuse drugs target various brain areas in the nervous system. Recent studies have shown that the prefrontal cortex (PFC) plays a key role in regulating addictive behaviors. The PFC is made up of excitatory glutamatergic cells and gamma-aminobutyric acid (GABAergic) interneurons. Recently, studies showed that GABA level was related with psychostimulant addiction. In this review, we will introduce the role and mechanism of GABA and γ-aminobutyric acid receptors (GABARs) of the PFC in regulating drug addiction, especially in psychostimulant addiction.

Co-occurrence of Psychopathology Problems in At-Risk Adolescents

No known studies have investigated co-occurrence of psychopathology problems in adolescents with biologic and/or environmental susceptibility, including prenatal drug exposure. This study identified comorbidity patterns of psychopathology problems by utilizing data from urban, primarily African American, youth, majority of whom were at heightened risk for exposure to drugs in utero. The roles of Research Domain Criteria (RDoC)-informed behavioral constructs of the Negative Valence (irritability) and Social Process Systems (social disinhibition) as antecedents of the comorbidity patterns were further examined. Lastly, the predictive validity of the identified patterns was evaluated in relation to emerging adulthood outcomes. Participants were 358 urban adolescents, primarily African Americans, drawn from a 21-year prospective birth-cohort study of the effects of prenatal drug exposure. Psychopathology problems were assessed at age 15. Irritability and social disinhibition were self-reported at age 12. Emerging adulthood outcomes were measured at age 21. Latent class modeling indicated four patterns: Normative (57%), substance-use (SU; 24%), mental-health-problems-without-substance-use (MH; 11%), and substance-use-and-other-mental-health-problems (SUMH; 7%). Higher irritability increased the odds of developing the MH pattern, whereas higher social disinhibition increased the odds of developing the SU pattern. The odds of manifesting the SUMH pattern were higher for children with higher irritability. For children with higher social disinhibition, the odds of manifesting the SUMH pattern were higher at a trend level. Adolescent comorbidity patterns were differentially associated with problematic tobacco and marijuana use and clinically relevant mental health problems in emerging adulthood, and completion of high school education. Peri-pubertal identification of individual differences in irritability and social disinhibition may mitigate the emergence of adolescent psychopathology, which could influence emerging adulthood adjustment in this at-risk population.

Psychotropic drug abuse in pregnancy and its impact on child neurodevelopment: A review

Substance abuse by women of child-bearing age and fetal in utero drug exposure has increased in the number of infants born with health issues. Prenatal exposure to psychoactive substances can lead to neurological and neurodevelopmental deficits later in life. Useful data concerning the effects of psychoactive drugs on fetal neurodevelopmental status are sparse. Understanding the neurodevelopmental consequences of prenatally drug-exposed children has become a pressing global concern. The aim of this review is to gather current evidence and information on neurodevelopmental outcomes of in utero drug exposure. A literature search was performed on the PubMed, Scopus, and Google Scholar databases using the terms “psychotropic drugs”, “neurodevelopmental consequences”, “prenatal drug exposure”, and “pregnancy”. Available studies on in utero drug exposure were reviewed and found to support the idea that some degree of health issues are present in fetuses and children. Different psychoactive substances have profound neurodevelopmental consequences, such as structural brain changes, poor attention span, Down syndrome, attention deficit hyperactivity disorder, autism spectrum disorder, imbalances in neurotransmitter levels, and many structural deficits. The pervasive use of psychoactive drugs in women of child-bearing age is an important health concern. Further scientific efforts are needed to investigate the effect of prenatal exposure to psychoactive drugs on children.

How prenatal exposures shape the infant brain: Insights from infant neuroimaging studies

Brain development during the prenatal period is rapid and unparalleled by any other time during development. Biological systems undergoing rapid development are at higher risk for disorganizing influences. Therefore, certain prenatal exposures impact brain development, increasing risk for negative neurodevelopmental outcome. While prenatal exposures have been associated with cognitive and behavioral outcomes later in life, the underlying macroscopic brain pathways remain unclear. Here, we review magnetic resonance imaging (MRI) studies investigating the association between prenatal exposures and infant brain development focusing on prenatal exposures via maternal physical health factors, maternal mental health factors, and maternal drug and medication use. Further, we discuss the need for studies to consider multiple prenatal exposures in parallel and suggest future directions for this body of research.

Sex-specific behavioral and neurogenic responses to cocaine in mice lacking and blocking dopamine D1 or dopamine D2 receptors

Adult neurogenesis in rodents is modulated by dopaminergic signaling and inhibited by cocaine. However, the sex-specific role of dopamine D1 and D2 receptors (D1R, D2R) in the deleterious effect of cocaine on adult neurogenesis has not been described yet. Here, we explored sex differences in (a) cell proliferation (5'-bromo-2'-deoxyuridine [BrdU]), (b) neural precursor (nestin), (c) neuronal phenotype (BrdU/β3-tubulin), and (d) neuronal maturity (NeuN) in the subventricular zone (SVZ) of the lateral ventricles and striatum of mice with genetic deletion (D1^-/- , D2^-/- ) or pharmacological blockage (SCH23390: 0.1 mg/kg/day/5 days; Raclopride: 0.3 mg/kg/day/5 days) of D1R and D2R, and treated (10 mg/kg/day/5 days) and then challenged (5 mg/kg, 48 hr later) with cocaine. Results indicated that hyperactivity responses to cocaine were absent in D1^-/- mice and reduced in SCH23390-treated mice. Activity responses to cocaine were reduced in D2^-/- males, but absent in D2^-/- females and increased in Raclopride-treated females. D1R deletion blocked the deleterious effect of cocaine on SVZ cell proliferation in males. Cocaine-exposed D1^-/- males also had reduced neuronal phenotype of SVZ newborn cells and increased striatal neuronal maturity. D2^-/- mice had lower proliferative and neural precursor responses. Cocaine in D2^-/- females or coadministered with Raclopride in wild-type females improved SVZ cell proliferation, an effect that positively correlated with plasma brain-derived neurotrophic factor (BDNF) concentrations. In conclusion, the sex-specific D1R and D2R signaling on SVZ cell proliferation, neural progenitor and neuronal maturity is differentially perturbed by cocaine, and BDNF may be required to link D2R to neuroplasticity in cocaine addiction in females.

Preconception maternal cocaine self-administration increases the reinforcing efficacy of cocaine in male offspring

RATIONALE

Although the influence of gestational cocaine exposure on offspring has been the focus of a sustained research effort, the effect of preconception cocaine self-administration by dams on progeny has received far less attention.

METHOD

In the current study, adult female rats were allowed to self-administer cocaine 2 h a day for 60 days and then after a 10-day wash out period, bred to naïve males. Maternal behavior was measured in dams until weaning. When male and female progeny reached adulthood, anxiety-like behavior, memory, and cocaine self-administration were assessed in separate cohorts of rats.

RESULTS

Despite a total of at least 30 days of cocaine abstinence, the quality of maternal behaviors was negatively affected by previous cocaine exposure as reflected by less time spent with pups as well as an excess of other maladaptive maternal behaviors. Measures of anxiety-like behavior and memory were not affected by maternal cocaine intake in either male or female offspring. In contrast, male, but not female, the progeny of dams exposed to cocaine showed increased reinforcing efficacy of cocaine as measured by cocaine self-administration under a progressive ratio schedule. The fact that cocaine self-administration was influenced only in the male offspring of cocaine-exposed dams argues against this phenotype being linked to altered maternal behavior, although this possibility cannot be ruled out completely.

CONCLUSIONS

Collectively, these results indicate that preconception cocaine self-administration by dams results in the relatively selective enhancement of cocaine addiction-like behavior in male offspring.

Developmental trajectories of externalizing behavior from ages 4 to 12: Prenatal cocaine exposure and adolescent correlates

BACKGROUND

Although prenatal cocaine exposure (PCE) has been linked with greater externalizing behavior, no studies have investigated heterogeneity of developmental trajectories in children with PCE to date. The present study aimed to: (1) identify developmental trajectories of externalizing problems in childhood by using a person-oriented analytic approach; (2) examine whether trajectories differ by PCE and other environmental and biological correlates; and (3) investigate how trajectories were associated with adolescent substance use and sexual behavior.

METHODS

Adolescents (N = 386; 197 PCE, 187 non-cocaine exposed (NCE)), primarily African-American and of low socioeconomic status, were prospectively enrolled in a longitudinal study at birth. Externalizing problems were assessed with the Child Behavior Checklist (CBCL) at ages 4, 6, 9, 10, 11, and 12. Substance (tobacco, alcohol, marijuana) use, via self-report and biologic assays, and early (before age 15) sexual intercourse were assessed at age 15.

RESULTS

Latent class growth modeling indicated four distinctive developmental trajectories of externalizing behavior from ages 4 to 12: low-decreasing group (32%); moderate-decreasing group (32%); accelerated risk group (14%); and elevated-chronic group (22%). PCE and maternal psychological distress interactively differentiated developmental trajectories of externalizing behavior, which were related to subsequent adolescent substance use and early sexual behavior differently across gender.

CONCLUSIONS

The two high-risk trajectories (accelerated risk and elevated-chronic groups), comprising 36% of the sample, identified in the present study may reflect multi-causality of early substance use and perhaps greater risk for transition to substance use disorders later in development.

Prenatal and concurrent cocaine, alcohol, marijuana, and tobacco effects on adolescent cognition and attention

BACKGROUND

Prenatal cocaine/polydrug exposure (PCE) may increase vulnerability to substance use disorders due to associated cognitive deficits. We examined whether neurocognitive deficits in executive functions and attention observed in PCE children persisted to adolescence when compared to non-cocaine/polydrug (NCE) children, and whether adolescent substance use (tobacco, alcohol, marijuana) was also associated with neurocognitive deficits.

METHODS

354 (180 PCE, 174 NCE) adolescents in a longitudinal study from birth were administered the Wechsler Intelligence Scales for Children - IV (WISC-IV), and the Integrated Visual and Auditory Continuous Performance Test (IVA/CPT) at age 15.5. Assessments of prenatal exposure to cocaine, alcohol, marijuana, and tobacco and measures of use at age 15.5 were taken. Confounding factors measured included lead, the caregiving environment, and violence exposure. Relationships between drug use and prenatal exposures on outcomes were assessed through multiple regression.

RESULTS

Adolescents with PCE had deficits in Perceptual Reasoning IQ and visual attention. Prenatal alcohol exposure predicted verbal and working memory IQ and visual and auditory attention deficits. Adolescent tobacco, alcohol, and marijuana use predicted attention in addition to PCE, lead and the caregiving environment.

CONCLUSION

Prenatal cocaine and alcohol exposure and adolescent use of substances are associated with neurocognitive deficits known to increase vulnerability to SUDs.

Maternal, fetal and neonatal consequences associated with the use of crack cocaine during the gestational period: a systematic review and meta-analysis

OBJECTIVE

Crack cocaine consumption is one of the main public health challenges with a growing number of children intoxicated by crack cocaine during the gestational period. The primary goal is to evaluate the accumulating findings and to provide an updated perspective on this field of research.

METHODS

Meta-analyses were performed using the random effects model, odds ratio (OR) for categorical variables and mean difference for continuous variables. Statistical heterogeneity was assessed using the I-squared statistic and risk of bias was assessed using the Newcastle-Ottawa Quality Assessment Scale. Ten studies met eligibility criteria and were used for data extraction.

RESULTS

The crack cocaine use during pregnancy was associated with significantly higher odds of preterm delivery [odds ratio (OR), 2.22; 95% confidence interval (CI), 1.59-3.10], placental displacement (OR, 2.03; 95% CI 1.66-2.48), reduced head circumference (- 1.65 cm; 95% CI - 3.12 to - 0.19), small for gestational age (SGA) (OR, 4.00; 95% CI 1.74-9.18) and low birth weight (LBW) (OR, 2.80; 95% CI 2.39-3.27).

CONCLUSION

This analysis provides clear evidence that crack cocaine contributes to adverse perinatal outcomes. The exposure of maternal or prenatal crack cocaine is pointedly linked to LBW, preterm delivery, placental displacement and smaller head circumference.

Evolutionary perspective on sex differences in the expression of neurological diseases

Sex-specific brain and cognitive deficits emerge with malnutrition, some infectious and neurodegenerative diseases, and often with prenatal or postnatal toxin exposure. These deficits are described in disparate literatures and are generally not linked to one another. Sexual selection may provide a unifying framework that integrates our understanding of these deficits and provides direction for future studies of sex-specific vulnerabilities. Sexually selected traits are those that have evolved to facilitate competition for reproductive resources or that influence mate choices, and are often larger and more complex than other traits. Critically, malnutrition, disease, chronic social stress, and exposure to man-made toxins compromise the development and expression of sexually selected traits more strongly than that of other traits. The fundamental mechanism underlying vulnerability might be the efficiency of mitochondrial energy capture and control of oxidative stress that in turn links these traits to current advances in neuroenergetics, stress endocrinology, and toxicology. The key idea is that the elaboration of these cognitive abilities, with more underlying gray matter or more extensive inter-modular white matter connections, makes them particularly sensitive to disruptions in mitochondrial functioning and oxidative stress. A framework of human sexually selected cognitive abilities and underlying brain systems is proposed and used to organize what is currently known about sex-specific vulnerabilities.

Biospecimens and the ABCD study: Rationale, methods of collection, measurement and early data

Biospecimen collection in the Adolescent Brain Cognitive Development (ABCD) study – of hair samples, shed deciduous (baby) teeth, and body fluids – will serve dual functions of screening for study eligibility, and providing measures of biological processes thought to predict or correlate with key study outcomes on brain and cognitive development. Biosamples are being collected annually to screen for recency of drug use prior to the neuroimaging or cognitive testing visit, and to store for the following future studies: (1) on the effects of exposure to illicit and recreational drugs (including alcohol and nicotine); (2) of pubertal hormones on brain and cognitive developmental trajectories; (3) on the contribution of genomics and epigenomics to child and adolescent development and behavioral outcomes; and (4) with pre- and post-natal exposure to environmental neurotoxicants and drugs of abuse measured from novel tooth analyses. The present manuscript describes the rationales for inclusion and selection of the specific biospecimens, methodological considerations for each measure, future plans for assessment of biospecimens during follow-up visits, and preliminary ABCD data to illustrate methodological considerations.

Altered functional connectivity to stressful stimuli in prenatally cocaine-exposed adolescents

BACKGROUND

Prenatal cocaine exposure (PCE) is linked to addiction and obesity vulnerability. Neural responses to stressful and appetitive cues in adolescents with PCE versus those without have been differentially linked to substance-use initiation. However, no prior studies have assessed cue-reactivity responses among PCE adolescents using a connectivity-based approach.

METHODS

Twenty-two PCE and 22 non-prenatally drug-exposed (NDE) age-, sex-, IQ- and BMI-matched adolescents participated in individualized guided imagery with appetitive (favorite-food), stressful and neutral-relaxing cue scripts during functional magnetic resonance imaging. Subjective favorite-food craving scores were collected before and after script exposure. A data-driven voxel-wise intrinsic connectivity distribution analysis was used to identify between-group differences and examine relationships with craving scores.

RESULTS

A group-by-cue interaction effect identified a parietal lobe cluster where PCE versus NDE adolescents showed less connectivity during stressful and more connectivity during neutral-relaxing conditions. Follow-up seed-based connectivity analyses revealed that, among PCE adolescents, the parietal seed was positively connected to inferior parietal and sensory areas and negatively connected to corticolimbic during both stress and neutral-relaxing conditions. For NDE, greater parietal connectivity to parietal, cingulate and sensory areas and lesser parietal connectivity to medial prefrontal areas were found during stress compared to neutral-relaxing cueing. Craving scores inversely correlated with corticolimbic connectivity in PCE, but not NDE adolescents, during the favorite-food condition.

CONCLUSIONS

Findings from this first data-driven intrinsic connectivity analysis of PCE influences on adolescent brain function indicate differences relating to PCE status and craving. These findings provide insight into the developmental impact of in utero drug exposure.

Association of prenatal cocaine exposure, childhood maltreatment, and responses to stress in adolescence

BACKGROUND

Prenatal cocaine exposure (PCE) may alter responses to stress. Children with PCE tend to grow up in suboptimal caregiving environments, conducive to child maltreatment (CM). Guided by the diathesis-stress model, the present study examined differences in self-reported responses to stress and coping in adolescents with and without PCE and explored whether childhood maltreatment (CM) moderated the effects of PCE.

METHODS

Adolescents (N=363; 184 PCE, 179 non-cocaine exposed (NCE)), primarily African-American and of low socioeconomic status, were prospectively enrolled in a longitudinal study at birth. The Responses to Stress Questionnaire was used to assess volitional coping (primary control, secondary control, disengagement) and involuntary responses (involuntary engagement, involuntary disengagement) to stress at the 15- and 17-year follow-up visits. CM was assessed retrospectively at age 17 using the Juvenile Victimization Questionnaire.

RESULTS

Findings from longitudinal mixed model analyses indicated that PCE was associated with poorer coping strategies only among adolescents with a history of CM. Adolescents with PCE who experienced CM reported less dominant use of primary (e.g., problem solving, emotional regulation) and secondary control (e.g., cognitive restructuring) and more dominant use of disengagement (e.g., denial, avoidance) and involuntary disengagement (e.g., inaction) than adolescents with PCE who did not experience CM or NCE adolescents regardless of CM. CM was associated with more dominant use of involuntary engagement (e.g., intrusive thoughts).

CONCLUSIONS

PCE may increase sensitivity to CM, predisposing increased vulnerability to environmental risk. Continued studies into adulthood will elucidate how coping and involuntary stress responses affect social, vocational, and behavioral adjustment.

The association of prenatal cocaine exposure, externalizing behavior and adolescent substance use

Prenatal cocaine exposure (PCE) may increase adolescent substance use through alterations of neurotransmitter systems affecting fetal brain development. The relationship between PCE and substance use at 15 and 17 years was examined. Subjects (365: 186 PCE; 179 non-cocaine exposed (NCE)) supplied biologic and self-report data using the Youth Risk Behavior Surveillance System (YRBSS) and Computerized Diagnostic Interview Schedule for Children (C-DISC 4) at ages 15 and 17. The relationship between PCE and substance use was assessed using General Estimating Equation (GEE) analyses controlling for confounding factors including violence exposure and preschool lead level. Teens with PCE vs. NCE teens were 2 times more likely to use tobacco (OR=2.1; 95% CI 1.21-3.63; p<.001) and marijuana (OR=1.85; CI 1.18-2.91; p<.001) and have a substance use disorder at age 17 (OR=2.51; CI 1.00-6.28; p<.05). Evaluation of PCE status by gender revealed an association between PCE and marijuana use that was more pronounced for boys than girls at 17 years. Violence exposure was also a significant predictor of alcohol (p<.001), tobacco (p<.05), and marijuana (p<.0006) use and substance abuse/dependence (p<.01). Externalizing behavior at age 12 fully mediated the effects of PCE on substance use disorder at age 17 and partially mediated effects of PCE on tobacco use, but did not mediate effects on marijuana use. The percentage of substance use reported increased between 15 and 17 years, with no differences between the PCE and NCE groups. Data suggest specialized drug use prevention measures for children with PCE may benefit this high risk group.

Trans-generational neurochemical modulation of methamphetamine in the adult brain of the Wistar rat

Chronic methamphetamine (METH) abuse has been shown to elicit strong neurotoxic effects. Yet, with an increasing number of children born to METH abusing mothers maturing into adulthood, one important question is how far do the neurotoxic effects of METH alter various neurotransmitter systems in the adult METH-exposed offspring. The purpose of this study was to investigate long-term trans-generational neurochemical changes, following prenatal METH exposure, in the adult Wistar rat brain. METH or saline (SAL-control animals) was administered to pregnant dams throughout the entire gestation period (G0-G22). At postnatal day 90, dopamine, serotonin, glutamate and GABA were measured in the adult brain before (baseline) and after a METH re-administration using in vivo microdialysis and liquid chromatography/mass spectrometry. The results show that METH-exposure increased basal levels of monoamines and glutamate, but decreased GABA levels in all measured brain regions. Acute challenge with METH injection in the METH-exposed group induced a lower increase in the monoamine system relative to the increase in the GABAergic and glutamatergic system. The data show that prenatal METH exposure has strong effects on the monoaminergic, GABAergic and glutamatergic system even when exposure to METH was limited to the prenatal phase. Toxicological effects of METH have therefore longer lasting effects as currently considered and seem to affect the excitatory-inhibitory balance in the brain having strong implications for cognitive and behavioral functioning.

Cocaine-induced neurodevelopmental deficits and underlying mechanisms

Exposure to drugs early in life has complex and long-lasting implications for brain structure and function. This review summarizes work to date on the immediate and long-term effects of prenatal exposure to cocaine. In utero cocaine exposure produces disruptions in brain monoamines, particularly dopamine, during sensitive periods of brain development, and leads to permanent changes in specific brain circuits, molecules, and behavior. Here, we integrate clinical studies and significance with mechanistic preclinical studies, to define our current knowledge base and identify gaps for future investigation. Birth Defects Research (Part C) 108:147-173, 2016. © 2016 Wiley Periodicals, Inc.

Longitudinal Effects of Embryonic Exposure to Cocaine on Morphology, Cardiovascular Physiology, and Behavior in Zebrafish

A sizeable portion of the societal drain from cocaine abuse results from the complications of in utero drug exposure. Because of challenges in using humans and mammalian model organisms as test subjects, much debate remains about the impact of in utero cocaine exposure. Zebrafish offer a number of advantages as a model in longitudinal toxicology studies and are quite sensitive physiologically and behaviorally to cocaine. In this study, we have used zebrafish to model the effects of embryonic pre-exposure to cocaine on development and on subsequent cardiovascular physiology and cocaine-induced conditioned place preference (CPP) in longitudinal adults. Larval fish showed a progressive decrease in telencephalic size with increased doses of cocaine. These treated larvae also showed a dose dependent response in heart rate that persisted 24 h after drug cessation. Embryonic cocaine exposure had little effect on overall health of longitudinal adults, but subtle changes in cardiovascular physiology were seen including decreased sensitivity to isoproterenol and increased sensitivity to cocaine. These longitudinal adult fish also showed an embryonic dose-dependent change in CPP behavior, suggesting an increased sensitivity. These studies clearly show that pre-exposure during embryonic development affects subsequent cocaine sensitivity in longitudinal adults.

A place for the hippocampus in the cocaine addiction circuit: Potential roles for adult hippocampal neurogenesis

Cocaine addiction is a chronic brain disease in which the drug seeking habits and profound cognitive, emotional and motivational alterations emerge from drug-induced neuroadaptations on a vulnerable brain. Therefore, a 'cocaine addiction brain circuit' has been described to explain this disorder. Studies in both cocaine patients and rodents reveal the hippocampus as a main node in the cocaine addiction circuit. The contribution of the hippocampus to cocaine craving and the associated memories is essential to understand the chronic relapsing nature of addiction, which is the main obstacle for the recovery. Interestingly, the hippocampus holds a particular form of plasticity that is rare in the adult brain: the ability to generate new functional neurons. There is an active scientific debate on the contributions of these new neurons to the addicted brain. This review focuses on the potential role(s) of adult hippocampal neurogenesis (AHN) in cocaine addiction. Although the current evidence primarily originates from animal research, these preclinical studies support AHN as a relevant component for the hippocampal effects of cocaine.

Pathways to adolescent sexual risk behaviors: Effects of prenatal cocaine exposure

BACKGROUND

To assess the impact of prenatal cocaine exposure (PCE) on adolescent sexual risk behaviors. Externalizing behavior, teen substance use, and early sexual intercourse were examined as pathways mediating the effects of PCE on sexual risk behaviors.

METHODS

Adolescents (N=364; 185 PCE, 179 non-cocaine exposure (NCE); 205 girls, 159 boys), primarily African-American and of low socioeconomic status, were prospectively enrolled in a longitudinal study at birth. Risky sexual behaviors were assessed at ages 15 and 17. Externalizing behavior at 12 years was assessed with the Youth Self-Report. Substance use, via self-report and biologic assays, and early (before age 15) sexual intercourse were assessed at age 15. Path analyses with the weighted least squares estimator with mean and variance adjustments were performed.

RESULTS

The final structural equation model-based path model, χ(2)=31.97 (df=27), p=.23, CFI=.99, TLI=.99, RMSEA=.021, WRMR=.695, indicated a direct effect of PCE on sexual risk behavior (β=.16, p=.02). Although PCE was related to greater externalizing behavior (β=.14, p=.009), which in turn, predicted early sexual intercourse (β=.16, p=.03), leading to sexual risk behavior (β=.44, p<.001), bootstrapping indicated a non-significant indirect effect (β=.01, p>.10). Substance use was correlated with early sexual intercourse (r=.60, p<.001) and predicted sexual risk behavior by age 17 (β=.31, p=.01).

CONCLUSIONS

Prenatal cocaine exposure was related to more engagement in sexual risk behaviors, suggesting the importance of reducing substance use among pregnant women as a means of prevention of offspring substance use and sexual risk behavior.

Delays in GABAergic interneuron development and behavioral inhibition after prenatal stress

Prenatal stress is associated with altered behavioral, cognitive, and psychiatric outcomes in offspring. Due to the importance of GABAergic systems in normal development and in psychiatric disorders, prenatal stress effects on these neurons have been investigated in animal models. Prenatal stress delays GABAergic progenitor migration, but the significance of these early developmental disruptions for the continued development of GABAergic cells in the juvenile brain is unclear. Here, we examined effects of prenatal stress on populations of GABAergic neurons in juvenile and adult medial frontal cortex (mFC) and hippocampus through stereological counting, gene expression, and relevant anxiety-like and social behaviors. Postnatally, the total GABAergic cell number that peaks in adolescence showed altered trajectories in mFC and hippocampus. Parvalbumin neuron proportion in juvenile brain was altered by prenatal stress, but parvalbumin gene expression showed no differences. In adult brain, parvalbumin neuron proportions were altered by prenatal stress with opposite gene expression changes. Adult prenatally stressed offspring showed a lack of social preference on a three-chambered task, increased anxiety-like behavior on the elevated plus maze, and reduced center time in an open field. Despite a lack of significant group differences in adult total GABAergic cell populations, performance of these tasks was correlated with GABAergic populations in mFC and hippocampus. In conclusion, prenatal stress resulted in a delay in GABAergic cell number and maturation of the parvalbumin subtype. Influences of prenatal stress on GABAergic populations during developmentally dynamic periods and during adulthood may be relevant to the anxiety-like behaviors that occur after prenatal stress. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 1078-1091, 2016.

Nucleosome Repositioning: A Novel Mechanism for Nicotine- and Cocaine-Induced Epigenetic Changes

Drugs of abuse modify behavior by altering gene expression in the brain. Gene expression can be regulated by changes in DNA methylation as well as by histone modifications, which alter chromatin structure, DNA compaction and DNA accessibility. In order to better understand the molecular mechanisms directing drug-induced changes in chromatin structure, we examined DNA-nucleosome interactions within promoter regions of 858 genes in human neuroblastoma cells (SH-SY5Y) exposed to nicotine or cocaine. Widespread, drug- and time-resolved repositioning of nucleosomes was identified at the transcription start site and promoter region of multiple genes. Nicotine and cocaine produced unique and shared changes in terms of the numbers and types of genes affected, as well as repositioning of nucleosomes at sites which could increase or decrease the probability of gene expression based on DNA accessibility. Half of the drug-induced nucleosome positions approximated a theoretical model of nucleosome occupancy based on physical and chemical characteristics of the DNA sequence, whereas the basal or drug naïve positions were generally DNA sequence independent. Thus we suggest that nucleosome repositioning represents an initial dynamic genome-wide alteration of the transcriptional landscape preceding more selective downstream transcriptional reprogramming, which ultimately characterizes the cell- and tissue-specific responses to drugs of abuse.