Prenatal cocaine exposure produces gender-specific motor effects in aged rats

Paternal Cocaine in Mice Alters Social Behavior and Brain Oxytocin Receptor Density in First Generation Offspring

It is well established that the damaging effects of drugs of abuse, such as cocaine, can extend beyond the user to their offspring. While most preclinical models of the generational effects of cocaine abuse have focused on maternal effects, we, and others, report distinct effects on offspring sired by fathers treated with cocaine prior to breeding. However, little is known about the effects of paternal cocaine use on first generation (F1) offspring's social behaviors. Here, we expand upon our model of oral self-administered paternal cocaine use to address the idea that paternal cocaine alters first generation offspring social behaviors through modulation of the oxytocin system. F1 cocaine-sired males displayed unaltered social recognition vs. non-cocaine sired controls but showed increased investigation times that were not related to altered olfaction. Paternal cocaine did not alter F1 male-aggression behavior or depression-like behaviors, but cocaine-sired males did display decreased anxiety-like behaviors. Female F1 behavior was similarly examined, but there were no effects of paternal cocaine. Cocaine-sired male mice also exhibited localized oxytocin receptor expression differences vs. controls in several brain regions regulating social behavior. These results provide evidence for effects of paternal cocaine exposure on social behaviors in male offspring with associated alterations in central oxytocin transmission.

Epigenetic effects of paternal cocaine on reward stimulus behavior and accumbens gene expression in mice

Paternal cocaine use causes phenotypic alterations in offspring behavior and associated neural processing. In rodents, changes in first generation (F1) offspring include drug reward behavior, circadian timing, and anxiety responses. This study, utilizing a murine (C57BL/6J) oral cocaine model, examines the effects of paternal cocaine exposure on fundamental characteristics of offspring reward responses, including: 1) the extent of cocaine-induced effects after different durations of sire drug withdrawal; 2) sex- and drug-dependent differences in F1 reward preference; 3) effects on second generation (F2) cocaine preference; and 4) corresponding changes in reward area (nucleus accumbens) mRNA expression. We demonstrate that paternal cocaine intake over a single ˜40-day spermatogenic cycle significantly decreased cocaine (but not ethanol or sucrose) preference in a sex-specific manner in F1 mice from sires mated 24 h after drug withdrawal. However, F1 offspring of sires bred 4 months after withdrawal did not exhibit altered cocaine preference. Altered cocaine preference also was not observed in F2's. RNASeq analyses of F1 accumbens tissue revealed changes in gene expression in male offspring of cocaine-exposed sires, including many genes not previously linked to cocaine addiction. Enrichment analyses highlight genes linked to CNS development, synaptic signaling, extracellular matrix, and immune function. Expression correlation analyses identified a novel target, Fam19a4, that may negatively regulate many genes in the accumbens, including genes already identified in addiction. Collectively, these results reveal that paternal cocaine effects in F1 offspring may involve temporally limited epigenetic germline effects and identify new genetic targets for addiction research.

Prostaglandin E2 is an endogenous modulator of cerebellar development and complex behavior during a sensitive postnatal period

Prostaglandins are lipid-derived molecules that mediate the generation of fever in the central nervous system. In addition to their proinflammatory role, prostaglandins also impact neuronal development and synaptic plasticity, sometimes in a sex-specific manner. The cerebellum has a high expression of prostaglandin receptors during development, but the role that these molecules play during normal cerebellar maturation is unknown. We demonstrate here that disrupting prostaglandin synthesis with cyclo-oxygenase inhibitors during a time-sensitive window in early postnatal life alters cerebellar Purkinje cell development in rats, resulting in initially increased dendritic growth in both sexes. We show that this results in later cerebellar atrophy in males only, resulting in a sex-specific loss of cerebellar volume. Further, although performance in motor tasks is spared, social interaction and the sensory threshold are altered in males developmentally exposed to cyclo-oxygenase inhibitors. This work demonstrates a previously unknown role for prostaglandins in cerebellar development and emphasizes the role that the cerebellum plays outside motor tasks, in cognitive and sensory domains that may help to explain its connection to complex neurodevelopmental disorders such as autism.

Development of inhibitory control among prenatally cocaine exposed and non-cocaine exposed youths from late childhood to early adolescence: The effects of gender and risk and subsequent aggressive behavior

The goal of the present investigation was to characterize the development of inhibitory control, an aspect of executive functions, in a sample of prenatally cocaine exposed (CE; n=165) children compared to an at risk, but prenatally cocaine unexposed (NCE; n=119) sample across time (i.e. 7.5 to 11.5 years of age). Gender and cumulative risk, a combination of postnatal medical (i.e. low birth weight and APGAR scores) and demographic risk, indexed by maternal educational attainment, were examined as predictors of change in inhibitory control across time and aggression was modeled as an outcome when children reached 14 years of age. Multiple group latent growth models indicated that CE children made more errors at 7.5 years of age during a standard Stroop interference task, however, over time CE children had greater age-related improvements, narrowing the initial gap, with NCE children in the ability to inhibit errors. Gender effects at 7.5 years within the NCE group were identified with NCE boys making initially more errors than NCE girls; both NCE and CE girls improved faster across development compared to NCE and CE boys, respectively. Greater cumulative risk was associated with more errors at 7.5 years in the CE and NCE groups. No differences were observed between CE and NCE children on time to complete the Stroop task at 7.5 years. However, NCE children had greater age-related improvements in their time to complete the Stroop interference task relative to their CE counterparts. NCE girls improved the fastest over time relative to NCE boys; a similar trend emerged (p<0.10) with CE girls improving faster over time than CE boys. Although all participants improved across development, higher cumulative risk in both groups was associated with slower age-related improvements (i.e. higher slopes) in the time to complete the Stroop task across development. After accounting for gender and cumulative risk, findings in both groups indicated that those who made more errors at 7.5 years of age and/or who had slower age-related changes (i.e. higher slopes) of time to complete the Stroop task across development were more aggressive as rated by caregivers at 14 years of age. Although qualified by gender and cumulative risk, these findings are consistent with reduced cognitive processing efficiency and executive function difficulties in CE children relative to NCE children. Findings suggest that executive function difficulties in CE children may be subtle as development continues to unfold over time. Furthermore, these findings indicate that development of inhibitory control may be an important mechanism linking prenatal cocaine exposure, gender, and cumulative risk to later adverse outcomes.

The effects of prenatal cocaine exposure and gender on inhibitory control and attention

Children exposed prenatally to cocaine show deficits in emotion regulation and inhibitory control. While controlling for the measures of medical complication in the perinatal period, environmental risk, and prenatal polydrug exposure (alcohol, tobacco, and marijuana), we examined the effects of prenatal cocaine exposure and gender on attention and inhibitory control in 203 children at ages 6, 9, and 11. Cocaine exposure affected the performance of males, but not females. Heavily exposed males showed deficits in the attention and the inhibition tasks. In addition, a significantly greater proportion of heavily exposed males (21%) than unexposed males (7%) or heavily exposed females (7%) failed to complete the task (p<0.01). Even without those poorest performing subjects, the overall accuracy for heavily exposed males (81%) was significantly reduced (p<0.05) compared to lightly exposed males (87%) and unexposed males (89%). The findings highlight the importance of considering gender specificity in cocaine exposure effects. Processes by which cocaine effects may be specific to males are discussed.

Steroids, sex and the cerebellar cortex: implications for human disease

Neurosteroids play an important role in the development of the cerebellum. In particular, estradiol and progesterone appear capable of inducing increases in dendritic spine density during development, and there is evidence that both are synthesized de novo in the cerebellum during critical developmental periods. In normal neonates and adults, there are few differences in the cerebellum between the sexes and most studies indicate that hormone and receptor levels also do not differ significantly during development. However, the sexes do differ significantly in risk of neuropsychological diseases associated with cerebellar pathology, and in animal models there are noticeable sex differences in the response to insult and genetic mutation. In both humans and animals, males tend to fare worse. Boys are more at risk for autism and Attention Deficit Hyperactivity Disorder than girls, and schizophrenia manifests at an earlier age in men. In rats males fare worse than females after perinatal exposure to polychlorinated biphenyls, and male mice heterozygous for the staggerer and reeler mutation show a more severe phenotype. Although very recent evidence suggests that differences in neurosteroid levels between the sexes in diseased animals may play a role in generating different disease phenotypes, the reason this hormonal difference occurs in diseased but not normal animals is currently unknown.

Children's cognitive ability from 4 to 9 years old as a function of prenatal cocaine exposure, environmental risk, and maternal verbal intelligence

This study examined the effects of prenatal cocaine exposure, environmental risk, and maternal verbal intelligence on children's cognitive ability. Gender and age were examined as moderators of potential cocaine exposure effects. The Stanford-Binet IV intelligence test was administered to 231 children (91 cocaine exposed, 140 unexposed) at ages 4, 6, and 9 years. Neonatal medical risk and other prenatal exposures (alcohol, cigarettes, and marijuana) were also examined for their unique effects on child IQ. Mixed models analysis indicated that prenatal cocaine exposure interacted with gender, as cocaine-exposed boys had lower composite IQ scores. Age at assessment did not moderate this relation, indicating that cocaine-exposed boys had lower IQs across this age period. A stimulating home environment and high maternal verbal IQ also predicted higher composite IQ scores. Cocaine-exposed boys had lower scores on the Abstract/Visual Reasoning subscale, with trends for lower scores on the Short-Term Memory and Verbal Reasoning subscales, as exposure effects were observed across domains. The findings indicate that cocaine exposure continues to place children at risk for mild cognitive deficits into preadolescence. Possible mechanisms for the Exposure x Gender interaction are discussed.

Reactivity and regulation in children prenatally exposed to cocaine

Children prenatally exposed to cocaine may be at elevated risk for adjustment problems in early development because of greater reactivity and reduced regulation during challenging tasks. Few studies have examined whether cocaine-exposed children show such difficulties during the preschool years, a period marked by increased social and cognitive demands and by rapid changes in reactivity and regulation. The authors addressed this question by examining frustration reactivity and regulation of behavior during a problem-solving task in cocaine-exposed and -unexposed preschoolers. Participants were 174 4.5-year-olds (M age = 4.55 years, SD = 0.09). Frustration reactivity was measured as latency to show frustration and number of disruptive behaviors, whereas regulation was measured as latency to approach and attempt the problem-solving task and number of problem-solving behaviors. Results indicated that cocaine-exposed children took longer to attempt the problem-solving task but that cocaine-exposed boys showed the most difficulties: They were quicker to express frustration and were more disruptive. Effect sizes were relatively small, suggesting both resilience and vulnerabilities.

Impact of in ovo-administered lead and testosterone on developing female thymocytes

The developing immune system is particularly sensitive to lead-induced immunotoxicity, but in some models, genders can differ in lead-induced immunotoxicity. Using an avian in ovo model of lead-induced T-helper disruption, the ability of in ovo administered lead and testosterone to alter thymocyte maturation among female embryos was investigated. On embryonic day (E) 8, Cornell K-strain embryos were given either testosterone (12.5 microg/egg in ethanol) or 15% ethanol in 100 microl volume. The groups then received either lead acetate (200 microg/egg) or sodium acetate (control) on E 12 of incubation. On E 20, thymocytes from 4-5 female embryos per group were analyzed by flow cytometry for cell surface markers CD3, CD4, CD8, TCR1, and TCR2. Lead alone did not induce any appreciable changes among the cell populations measured in this study. However, when testosterone treatment was followed by lead (testosterone + lead), there was a significant increase in CD4+CD8+ double-positive cells compared with either control or lead treatment groups. Testosterone, either by itself or in combination with lead, significantly reduced the percentage of cells with the CD4+CD8- phenotype when compared to the lead alone group. No change was detected with respect to the CD4-CD8+, CD4-CD8-, TCR1+, and TCR2+ phenotypes following any treatment. Therefore, sex hormonal balance in early life appears to influence the manner in which the developing thymus responds to the heavy metal lead.

Aggression at age 5 as a function of prenatal exposure to cocaine, gender, and environmental risk

OBJECTIVE

To examine childhood aggression at age 5 in a multiple risk model that includes cocaine exposure, environmental risk, and gender as predictors.

METHODS

Aggression was assessed in 206 children by using multiple methods including teacher report, parent report, child's response to hypothetical provocations, and child's observed behavior. Also examined was a composite score that reflected high aggression across contexts.

RESULTS

Multiple regression analyses indicated that a significant amount of variance in each of the aggression measures and the composite was explained by the predictors. The variables that were independently related differed depending on the outcome. Cocaine exposure, gender, and environmental risk were all related to the composite aggression score.

CONCLUSIONS

Cocaine exposure, being male, and a high-risk environment were all predictive of aggressive behavior at 5 years. It is this group of exposed boys at high environmental risk that is most likely to show continued aggression over time.

Sexual dimorphism in cerebellar structure, function, and response to environmental perturbations

Sexual dimorphism of CNS structure and function has been observed in humans and animals, but remains relatively unrecognized in the context of the cerebellum. Recent research in our laboratory has examined whether these gender differences extend to cerebellar structure and function, as well as the impact of environmental factors on the developing cerebellum. Perinatal exposure to both chemical and physical perturbations in the environment (in our experiments, PCBs or hypergravity) affects growth, neurodevelopment, and motor coordination differently in males and females. These neurodevelopmental and behavioral effects are accompanied by sex-related changes in cerebellar mass and cerebellar protein expression. Exposure to chemical toxins (PCBs) resulted in more dramatic neurodevelopmental and behavioral changes in male neonates. It is possible that gender-related differences in male and female cerebellar structure and function are related to sex-specific development of the cerebellum and sex-specific distribution of specific receptors, local synthesis of trophic factors, and maturation of the pituitary hypophesial axis. These sex-related differences may underlie the sex-specific preponderance of certain neuropsychiatric disorders, and must be incorporated in the design of future basic and clinical investigations.

Prenatal cocaine: quantity of exposure and gender moderation

Animal but few human studies have demonstrated gender-influenced differences in outcome related to prenatal cocaine exposure. Pregnant participants in a prospective pregnancy study were interviewed for drug use. Exposure was considered positive if history or laboratory tests were positive. An ordinal measure of exposure was also constructed. Six years later, the child and primary caretaker were tested to assess drug use in the home since birth and teacher-assessed child behavior. Data were complete for 473 children (204 cocaine exposed). Twenty-four of the exposed children (12%) were considered to have persistent pregnancy exposure based on positive urine screen at delivery. Boys with any prenatal cocaine exposure scored significantly higher (more problem behaviors) than nonexposed boys on the hyperactivity item. In contrast, no similar cocaine effect was observed for girls. When cocaine exposure was expressed as the three-level ordinal variable, boys, but not girls, with persistent exposure had more behavior problems (0.5 to 1.0 SD higher). Even after control for important covariates, boys with persistent exposure had more problems in central processing, motor skills, handling abstract concepts, and passivity to the environment. The magnitude of the relations reported in this research were moderate to large. In summary, both gender and the level of exposure had a significant behavioral effect on school-age behavior. In these analyses, the behavior of boys, but not girls, prenatally exposed to cocaine was significantly and negatively affected, and these findings remained after control for covariates, including prenatal alcohol or other illicit drug exposures and postnatal drug use in the home.

Prenatal cocaine exposure decreases nigrostriatal dopamine release in vitro: Effects of age and sex

The present study examined the effects of prenatal cocaine (PCOC) exposure, age, sex, and estrous phase on the functional development of nigrostriatal dopamine (DA) neurons. Striatal tissue was obtained from prepubescent and adult rats of both sexes after bidaily exposure to saline (1 ml/kg) or cocaine (20 mg/kg/ml saline) from embryonic days 15-21. Tissue levels, basal release, and electrically evoked (1 or 8 Hz) overflow of endogenous DA and its metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), as well as their efflux in response to superfusion with the DA transport blocker, nomifensine (10 microM), were measured from superfused striatal slices. Generally, these measures were highest in tissue from males and adults. Tissue DA and DOPAC levels and the rate of DA turnover were unaffected by PCOC exposure. Slices from PCOC-exposed juvenile and adult male rats exhibited significantly reduced basal and electrically evoked DA release at both stimulation intensities, in conjunction with higher levels of presynaptic DA reuptake. Female rats were largely spared from the effects of PCOC exposure, and measures did not vary with estrous phase. These findings demonstrate that the effects of PCOC exposure on various parameters of nigrostriatal DA neuronal function are not uniform across age, sex, or phases of the estrous cycle. These novel alterations in nigrostriatal DA transmission are in need of independent replication, but they may have profound implications for behavioral activities regulated by these neurons and, thus, may provide a basis for sex-selective effects of PCOC in exposed humans. Possible mechanisms of deleterious effects of PCOC exposure in select groups are discussed.

Prenatal exposure to cocaine decreases adenylyl cyclase activity in embryonic mouse striatum

Adenylyl cyclase activity was measured in the striatum of naive mice as a function of age and in mice exposed in utero to cocaine. In naive Swiss-Webster mice, basal and forskolin-stimulated adenylyl cyclase activity increased gradually from embryonic day 13 (E13) until 2-3 weeks of age when activity peaked before decreasing slightly to adult levels. The ability of the dopamine D1 receptor agonist, SKF 82958, to stimulate adenylyl cyclase activity also increased in magnitude until P15. In a separate study, pregnant Swiss-Webster mice were injected twice daily with cocaine (15 mg/kg, s.c.) or an equal volume of saline from E10 to E17. Adenylyl cyclase activity was measured in the striatum of E18 embryos. Basal adenylyl cyclase activity was significantly reduced following prenatal exposure to cocaine. Likewise, the ability of forskolin or SKF 82958 to stimulate adenylyl cyclase was attenuated following cocaine exposure. DeltaFosB was not induced, contrary to what is seen in adult mice. These results demonstrate a functional change in a critical signal transduction pathway following chronic in utero exposure to cocaine that might have profound effects of the development of the brain. Alterations in the cAMP system may underlie some of the deficits seen in humans exposed in utero to cocaine.

Inhibitory motor control at five years as a function of prenatal cocaine exposure

This study examined children's (n = 140, age 5 years) ability to inhibit a motor response as a function of prenatal cocaine exposure. We hypothesized that cocaine-exposed children would perform worse than unexposed children on the Contrary Tapping task. Results indicated that cocaine exposure, high environmental risk, male gender, and low child IQ each were related to poorer inhibitory control. An interaction indicated that cocaine effects were specific to children who lived in relatively low-risk environments. Cocaine-exposed children made an error sooner than unexposed children in low-risk environments but in the same trial as both exposed and unexposed children living in high-risk environments. Potential underlying mechanisms and the importance of examining cocaine exposure effects in the context of children's existing environment are discussed.

Prenatal cocaine and/or nicotine exposure produces depression and anxiety in aging rats

The adult use of cocaine and nicotine has been linked to depression and/or anxiety. Changes in emotional behavior were assessed using behavioral paradigms developed as animal analogs of psychiatric disorders in 12-14 month old Sprague-Dawley rats exposed daily on gestational days 8-20 to cocaine and nicotine, either alone or in combination. Results from the elevated plus maze (EPM), used to assess anxiety-related behaviors, indicated that offspring prenatally exposed to either high-dose cocaine (40 mg/kg/day) or high-dose nicotine (5.0 mg/kg/day) were less timid/more impulsive. Animals from these two groups spent the most time on the open arms, and had the highest percentage of entries into the open arms of the EPM. Combined in utero exposure to cocaine and nicotine nullified these effects. Cocaine challenge (20 mg/kg) did not interact with prenatal treatment, but increased activity on all arms of the EPM in all groups. Sucrose preference was used as a measure of anhedonia, a cardinal symptom of depressive illness. Reduced sucrose preference was seen only in the group of offspring prenatally exposed to high-dose cocaine (40 mg/kg) plus low-dose nicotine (2.5 mg/kg/day). Exposure to a water-deprivation stress normalized sucrose preference in this group, without altering preference or intake in the other prenatal treatment groups. Transient hyperactivity was seen in the offspring of dams treated with high-dose nicotine, an effect that was again reversed in combined drug groups. Traditional gender differences in activity levels and sucrose intake, that is, females greater than males, were still evident in this population of aging rats. These data indicate that prenatal exposure to cocaine and/or nicotine has long-term effects on emotional behavior. Combined drug exposure contributed to the development of depressive symptoms, but not anxiety-like behavior, in a dose-dependent manner. In contrast, exposure to high doses of either drug alone reduced cautionary behavior. Data from this line of research could provide insight into the pathogenesis of emotional disorders, especially during the aging process.

Prenatal cocaine effects on fear conditioning: exaggeration of sex-dependent context extinction

Prenatal cocaine exposure results in deficits in sensory preconditioning, discrimination reversal, and spatial navigation, tasks that require input from the hippocampus. However, there are no previous studies concerning prenatal cocaine effects on contextual fear conditioning, another hippocampal-dependent task. The present experiments tested whether chronic subcutaneous administration of 40 mg/kg of cocaine HCl to pregnant rats, from gestational day (GD) 8 through 20 would lead to disruption of contextual fear conditioning in adult male and female offspring. Offspring of saline-injected/pair-fed and untreated dams served as controls. Experiment 1 used a one-trial context conditioning preparation. Rats received a 2-s, 1-mA footshock in either the test context or a novel context, or received no shock on the day prior to the no-shock test. Defecation and freezing were measures of fear. Experiment 2 used a multiple measures protocol to optimize detection of prenatal treatment effects and was preceded by an open-field test. Rats received a 2-s, 0.8-mA footshock or no shock once daily over 4 days of conditioning. During 3 days of extinction, access to an adjacent chamber enabled the observation of four additional measures of fear: side crossing, latency, nose crossing, and side-differential. There were gender-dependent effects of conditioning on freezing and the four added measures of fear. Males showed higher levels of context conditioning and extinguished more slowly than females. The measures of nose crossing and side-differential revealed that prenatal cocaine exposure exaggerated gender-specific effects of context conditioning. The effects of prenatal cocaine exposure on context extinction are sexually dimorphic.

Prenatal cocaine exposure disrupts non-spatial, short-term memory in adolescent and adult male rats

The rise in the recreational use of cocaine in the last two decades has resulted in a growing health concern about fetal drug exposure. In exposed children, investigators have noted altered cognitive performance in complex or distracting, but not more controlled, situations. In rodent models, deficits in short-term memory have been noted in some, but not all, paradigms, although these studies also differ in routes of administration and dosing models. Here, we report short-term memory deficits in rats prenatally exposed to cocaine using an intravenous administration model to closer mimic cocaine doses and pharmacokinetics seen with human use. A spontaneous two object recognition task was used to avoid (1) clearly aversive or rewarding components, (2) reference memory component and (3) the use of external motivators, such as swimming stress or food deprivation/rewards. In this task, adolescent and adult male rats exposed to cocaine in utero demonstrated deficits in short-term memory compared with saline controls. No difference in the time spent exploring the objects or the number of failures was noted between the prenatal cocaine and saline rats. This study suggests that prenatal exposure to cocaine can result in a long-lasting deficit in non-spatial, short-term memory in a spontaneously performed task.

Effects of age and gender but not prenatal cocaine on random ratio and delayed spatial alternation responding in rats

This investigation employed a longitudinal analysis of rat operant behavior under two different schedules of reinforcement following prenatal exposure to cocaine. Offspring were derived from four maternal exposure groups: 50 mg/kg cocaine, their pair-fed controls, 25 mg/kg cocaine, and freely fed controls. Cocaine was administered via gavage from gestation day 6-20. A maternal fostering procedure was used. Pairs of male and female littermates were assigned to a 7-, 14-, or 21-month cohort and at the appropriate age were trained to respond on one lever in a two-lever operant chamber. Reinforcement was delivered with a series of random ratio (RR) schedules where the RR value was increased across sessions. After RR training, animals were examined with a delayed spatial alternation (DSA) procedure in the same chambers. Male offspring responded at higher rates than females during high-probability RR schedules, whereas advancing age was associated with lower response rates during low-probability RR schedules in both males and females. Prenatal cocaine exposure exerted only limited effects on RR responding during transition and did not affect DSA behavior. The results of this longitudinal analysis suggest that prenatal cocaine does not exert global or far-reaching learning deficits in prenatally exposed rats.