An assessment of the long-term developmental and behavioral teratogenicity of prenatal nicotine exposure

Prenatal exposure to environmental tobacco smoke alters gene expression in the developing murine hippocampus

BACKGROUND

Little is known about the effects of passive smoke exposures on the developing brain.

OBJECTIVE

The purpose of the current study was to identify changes in gene expression in the murine hippocampus as a consequence of in utero exposure to sidestream cigarette smoke (an experimental equivalent of environmental tobacco smoke (ETS)) at exposure levels that do not result in fetal growth inhibition.

METHODS

A whole body smoke inhalation exposure system was utilized to deliver ETS to pregnant C57BL/6J mice for 6 h/day from gestational days 6-17 (gd 6-17) [for microarray] or gd 6-18.5 [for fetal phenotyping].

RESULTS

There were no significant effects of ETS exposure on fetal phenotype. However, 61 "expressed" genes in the gd 18.5 fetal hippocampus were differentially regulated (up- or down-regulated by 1.5-fold or greater) by maternal exposure to ETS. Of these 61 genes, 25 genes were upregulated while 36 genes were down-regulated. A systems biology approach, including computational methodologies, identified cellular response pathways, and biological themes, underlying altered fetal programming of the embryonic hippocampus by in utero cigarette smoke exposure.

CONCLUSIONS

Results from the present study suggest that even in the absence of effects on fetal growth, prenatal smoke exposure can alter gene expression during the "early" period of hippocampal growth and may result in abnormal hippocampal morphology, connectivity, and function.

Educational attainment and smoking among women: risk factors and consequences for offspring

We examine the association between education and smoking by women in the population, including smoking during pregnancy, and identify risk factors for smoking and the consequences of smoking in pregnancy for children's smoking and behavioral problems. Secondary analyses of four national data sets were implemented: The National Survey of Drug Use and Health (2006), the National Longitudinal Survey of Youth (1979-2004); the National Longitudinal Survey of Adolescent Health (Wave III); National Health and Nutrition Examination Survey (2005-2006). The lower the level of education, the greater the risk of being a current smoker, smoking daily, smoking heavily, being nicotine dependent, starting to smoke at an early age, having higher levels of circulating cotinine per cigarettes smoked, and continuing to smoke in pregnancy. The educational gradient is especially strong in pregnancy. Educational level and smoking in pregnancy independently increase the risk of offspring smoking and antisocial and anxious/depressed behavior problems. These effects persist with control for other covariates, except maternal age at child's birth, which accounts for the impact of education on offspring smoking and anxious/depressed behavior problems. Women with low education should be the target of public health efforts toward reducing tobacco use. These efforts need to focus as much on social conditions that affect women's lives as on individual level interventions. These interventions would have beneficial effects not only for the women themselves but also for their offspring.

Simultaneous prenatal ethanol and nicotine exposure affect ethanol consumption, ethanol preference and oxytocin receptor binding in adolescent and adult rats

Ethanol consumption and smoking during pregnancy are common, despite the known adverse effects on the fetus. The teratogenicity of each drug independently is well established; however, the effects of concurrent exposure to ethanol and nicotine in preclinical models remain unclear. This study examined the impact of simultaneous prenatal exposure to both ethanol and nicotine on offspring ethanol preference behaviors and oxytocin system dynamics. Rat dams were given liquid diet (17% ethanol derived calories (EDC)) on gestational day (GD) 5 and 35% EDC from GD 6-20 and concurrently an osmotic minipump delivered nicotine (3-6mg/kg/day) from GD 4-postpartum day 10. Offspring were tested for ethanol preference during adolescence (postnatal day (PND) 30-43) and again at adulthood (PND 60-73), followed by assays for oxytocin mRNA expression and receptor binding in relevant brain regions. Prenatal exposure decreased ethanol preference in males during adolescence, and decreased consumption and preference in females during adulthood compared to controls. Oxytocin receptor binding in the nucleus accumbens and hippocampus was increased in adult prenatally exposed males only. Prenatal exposure to these drugs sex-specifically decreased ethanol preference behavior in offspring unlike reports for either drug separately. The possible role of oxytocin in reduction of ethanol consumption behavior is highlighted.

Impaired postnatal growth of infants prenatally exposed to cigarette smoking

Most of the previous studies have shown a significant inverse relationship between smoking during pregnancy and weight, height and head circumference of infants at birth, but there is limited literature that assesses the head circumference measures of infants of smoker mothers in postnatal follow-up. The aim of this study was to assess the effects of maternal smoking and passive smoking during pregnancy on postnatal anthropometric measures of infants. Infants were divided into 3 groups: infants of smokers (n = 48), passive smokers (n = 57) and nonsmokers (n = 54), and were evaluated for their weight, height and head circumference at birth, 3 months and 6 months of age. Infants of smokers showed significant weight and head circumference deficits at birth compared to nonsmokers' infants (p < 0.05 and p < 0.001, respectively). At 6 months of age, infants of smokers continued to show significant deficits in all 3 measures compared to nonsmokers' infants (p < 0.001 for each), and infants of passive smokers showed only marginal decreases. Moreover, the weight and height growth velocities of the smokers' infants remained deficient, whereas their growth velocity of the head circumferences increased from birth up to 6 months and reached the growth velocity of the nonsmokers' infants. Infants of passive smokers showed a complete catch-up growth at 6 months. This study indicates that smoking during pregnancy results in serious deficits in infants' growth even after birth. Therefore, it is essential to inform smoker women before pregnancy the possible growth retardation of infants.

Effects of postnatal parental smoking on parent and teacher ratings of ADHD and oppositional symptoms

To assess the effects of postnatal parental smoking on subsequent parent and teacher ratings of DSM-IV attention deficit hyperactivity disorder (ADHD) symptoms and oppositional behaviors in children diagnosed with ADHD and their siblings. Children between 5 and 12 years of age with ADHD and their siblings were included. DSM-IV ADHD symptom subscales (Inattentive and hyperactive-impulsive), and oppositionality subscale scores from Conners' Rating Scales were predicted on the basis of parental smoking status in the first 7 years after birth using Generalized Estimating Equations controlling for a range of relevant covariates. Postnatal parental smoking was associated with both parent and teacher ratings of ADHD symptoms and oppositional behavior. After controlling for a number of covariates, several of these relationships were still significant. The risk of maternal smoking for the development of ADHD symptoms does not end during pregnancy. Research on the mechanisms underlying the observed associations is needed.

Prenatal exposure to drugs: effects on brain development and implications for policy and education

The effects of prenatal exposure to drugs on brain development are complex and are modulated by the timing, dose and route of drug exposure. It is difficult to assess these effects in clinical cohorts as these are beset with problems such as multiple exposures and difficulties in documenting use patterns. This can lead to misinterpretation of research findings by the general public, the media and policy makers, who may mistakenly assume that the legal status of a drug correlates with its biological impact on fetal brain development and long-term clinical outcomes. It is important to close the gap between what science tells us about the impact of prenatal drug exposure on the fetus and the mother and what we do programmatically with regard to at-risk populations.

Growth retardation of fetal rats exposed to nicotine in utero: possible involvement of CYP1A1, CYP2E1, and P-glycoprotein

To elucidate the possible metabolic mechanism of intrauterine growth retardation induced by nicotine, this study determines the effects of prenatal nicotine exposure on fetal development and cytochrome P4501A1 (CYP1A1), CYP2E1, and P-glycoprotein (Pgp) expression in maternal liver and placenta. Pregnant rats were given 1.0 mg/kg nicotine subcutaneously twice a day from gestational day (GD) 8 to GD 15, 18, or 21. In nicotine-treated groups, fetal developmental parameters including body weight were significantly lower. The activities of CYP1A1 and CYP2E1 in maternal liver microsomes in nicotine-treated groups increased significantly with progressing gestation when compared with the corresponding control, but returned to the level similar to the control in late pregnancy. Nicotine-treated groups induced pathological changes and increased malondialdehyde (MDA) content in the placenta when compared with the control. The gene expressions of CYP1A1 and CYP2E1 in the placenta increased significantly in nicotine-treated groups on GD 15 and GD 18, but returned to the level similar to the corresponding control on GD 21. In nicotine group, there was a decrease of mdr1a expression on GD 15, GD 18, and GD 21, with the most significant decrease on GD 15. In contrast, no significant difference was found in mdr1b mRNA expression between the nicotine-treated animals and the corresponding control. In comparison with the corresponding control, the placental Pgp protein significantly decreased on GD 15 and GD 18. Our results showed that prenatal nicotine exposure resulted in inhibition of fetal growth significantly. The induction of CYP2E1 and CYP1A1 gene expression by nicotine in the maternal liver and placenta may be involved with the observed increase in oxidative stress and lipid peroxidation. The inhibition of the placental Pgp expression by nicotine may also contribute to an increased susceptibility of the fetus to environmental toxins.

Gene-environment interactions across development: Exploring DRD2 genotype and prenatal smoking effects on self-regulation

Genetic factors dynamically interact with both pre- and postnatal environmental influences to shape development. Considerable attention has been devoted to gene-environment interactions (G x E) on important outcomes (A. Caspi & T. E. Moffitt, 2006). It is also important to consider the possibility that these G x E effects may vary across development, particularly for constructs like self-regulation that emerge slowly, depend on brain regions that change qualitatively in different developmental periods, and thus may be manifested differently. To illustrate one approach to exploring such developmental patterns, the relation between variation in the TaqIA polymorphism, related to D2 dopamine receptor expression and availability, and prenatal exposure to tobacco was examined in two exploratory studies. First, in 4-week-old neonates, genotype-exposure interactions were observed for attention and irritable reactivity, but not for stress dysregulation. Second, in preschool children, genotype was related to Preschool Trail Making Test (K. A. Espy and M. F. Cwik, 2004) task performance on conditions requiring executive control; children with both the A1+ genotype and a history of prenatal tobacco exposure displayed disproportionately poor performance. Despite study limitations, these results illustrate the importance of examining the interplay between genetic and prenatal environmental factors across development.

Understanding development and prevention of chronic physical aggression: towards experimental epigenetic studies

The aim of this paper was to highlight how developmental psychopathology, epigenetics and prevention experiments are starting to blend together to explain the developmental causes of chronic physical aggression (CPA) and, more importantly, to help prevent CPA and its associated physical, mental and social problems. After defining the keywords (prevention, chronic and physical aggression), a selected review of published studies is used to answer the following four questions: when should we attempt to prevent onset of CPA? What are the risk factors for CPA? Have early childhood interventions been shown to prevent CPA? Can early preventive interventions benefit from epigenetic studies? The last section of this paper gives two examples of experimental prevention designs that integrate present knowledge of CPA development, risk factors, early childhood preventive interventions and epigenetic programming of brain development during pregnancy and early childhood. I conclude that randomized control trials of preventive interventions during pregnancy and early childhood with a specific focus on epigenetic effects are the research design most likely to advance our understanding of the biopsychosocial mechanisms that lead to CPA, and the only research design that can identify effective interventions for preventing the development of CPA.

Maternal tobacco smoking, nicotine replacement and neurobehavioural development

Abstract The adverse effects of prenatal cigarette smoke exposure on human reproductive outcomes are a major scientific and public health concern. In the United States, approximately 25% of women of childbearing age currently smoke cigarettes, and only a small percentage of these individuals quit after learning of their pregnancy. Women interested in smoking cessation during pregnancy have a number of options, including behavioural and pharmacological aids, but nicotine replacement therapy (NRT) is by far the most common approach. While NRT avoids exposure to the myriad compounds present in tobacco smoke, nicotine itself causes damage to the developing nervous system. The purpose of this article is to review the detrimental effects of developmental tobacco smoke exposure on short- and long-term outcomes with particular emphasis on neurobehavioural consequences. In conclusion based on the clear, adverse effects of nicotine on brain development observed in human and animal studies, we suggest that safer alternatives for smoking cessation in pregnancy are badly needed.

Acute nicotine activates c-fos and activity-regulated cytoskeletal associated protein mRNA expression in limbic brain areas involved in the central stress-response in rat pups during a period of hypo-responsiveness to stress

In adult rats, acute nicotine, the major psychoactive ingredient in tobacco smoke, stimulates the hypothalamic-pituitary-adrenal axis (HPA), resulting in activation of brain areas involved in stress and anxiety-linked behavior. However, in rat pups the first two postnatal weeks are characterized by hypo-responsiveness to stress, also called the 'stress non-responsive period' (SNRP). Therefore, we wanted to address the question if acute nicotine stimulates areas involved in the stress response during SNRP. To determine neuronal activation, the expression of the immediate-early genes c-fos and activity-regulated cytoskeletal associated protein (Arc) was studied in the central nucleus of the amygdala (CeA), bed nucleus stria terminalis (BST) and paraventricular hypothalamic nucleus (PVN), which are areas involved in the neuroendocrine and central stress response. Rat pups received nicotine tartrate (2 mg/kg) or saline by i.p. injection at postnatal days (P) 5, 7 and 10 and their brains were removed after 30 min. We used semi-quantitative radioactive in situ hybridization with gene specific antisense cRNA probes in coronal sections. In control pups, c-fos expression was low in most brain regions, but robust Arc hybridization was found in several areas including cingulate cortex, hippocampus and caudate. Acute nicotine resulted in significant induction of c-fos expression in the PVN and CeA at P5, P7 and P10, and in the BST at P7 and P10. Acute nicotine significantly induced expression of Arc in CeA at P5, P7 and P10, and in the BST at P10. In conclusion, acute nicotine age dependently activated different brain areas of the HPA axis during the SNRP. After P7, the response was more pronounced and included the BST, suggesting differential maturation of the HPA axis in response to nicotine.

Nicotine-induced plasticity during development: modulation of the cholinergic system and long-term consequences for circuits involved in attention and sensory processing

Despite a great deal of progress, more than 10% of pregnant women in the USA smoke. Epidemiological studies have demonstrated correlations between developmental tobacco smoke exposure and sensory processing deficits, as well as a number of neuropsychiatric conditions, including attention deficit hyperactivity disorder. Significantly, data from animal models of developmental nicotine exposure have suggested that the nicotine in tobacco contributes significantly to the effects of developmental smoke exposure. Consequently, we hypothesize that nicotinic acetylcholine receptors (nAChRs) are important for setting and refining the strength of corticothalamic-thalamocortical loops during critical periods of development and that disruption of this process by developmental nicotine exposure can result in long-lasting dysregulation of sensory processing. The ability of nAChR activation to modulate synaptic plasticity is likely to underlie the effects of both endogenous cholinergic signaling and pharmacologically administered nicotine to alter cellular, physiological and behavioral processes during critical periods of development.

Gestational ethanol and nicotine exposure: effects on maternal behavior, oxytocin, and offspring ethanol intake in the rat

Alcohol consumption and smoking during pregnancy is common, despite the known adverse effects of these drugs on fetal development. Though studies on the effects of each drug separately are published, little is known about the effect of concurrent use of alcohol and nicotine in humans or in preclinical models. In this report, we examined the impact of continuous gestational exposure to both ethanol via liquid diet and nicotine via an osmotic minipump on maternal behavior, offspring ethanol intake, and oxytocin levels in a rat model. Dams were tested for the onset of maternal behavior with litters of unexposed surrogate pups and then killed to examine oxytocin levels within specific brain regions. Drug-exposed offspring reared by surrogate dams were tested for ethanol intake at either adolescence or adulthood, and oxytocin levels were measured in relevant brain regions after behavioral tests. Dams exhibited minor deficits in maternal care, which were associated with lower oxytocin levels in both the ventral tegmental and medial preoptic areas compared to control dams. Prenatal exposure altered sex-specific ethanol intake, with differential effects at adolescence and adulthood. Oxytocin system changes were also apparent in the ventral tegmental and medial preoptic regions of drug-exposed adolescent and adult offspring. These results suggest that dam treatment with ethanol and nicotine can somewhat negatively affect the early rearing environment, and that prenatal exposure to both of these drugs results in drinking behavior differing from what would be expected from either drug alone. Oxytocin's possible involvement in the mediation of these effects is highlighted.

Prenatal smoking and internalizing and externalizing problems in children studied from childhood to late adolescence

OBJECTIVE

To study whether prenatal smoking only relates to externalizing problems or whether it is associated with both internalizing and externalizing problems from childhood into late adolescence.

METHOD

Child Behavior Checklist-derived, parent-reported internalizing and externalizing problems of 396 children were longitudinally assessed at ages 5, 10 to 11, and 18 years. The influence of self-reported prenatal smoking on the course of internalizing and externalizing problems over these ages was assessed, controlling for the co-occurrence of internalizing and externalizing problems and co-occurring pre- and perinatal risk factors, demographic characteristics, maternal mental health, and child social and attention problems.

RESULTS

Children whose mothers had smoked during pregnancy had increased levels of both internalizing and externalizing problems over the period of ages 5 to 18 years when compared with children whose mothers did not smoke during pregnancy. These associations remained significant after controlling internalizing for externalizing and vice versa and possible confounding variables.

CONCLUSIONS

Maternal smoking during pregnancy is a predictor of internalizing as well as externalizing psychopathology in offspring. The association between prenatal smoking and internalizing and externalizing problems persists throughout childhood and late adolescence.

Neurobiology of attention deficit hyperactivity disorder

This article addresses the current understanding of the neurobiological bases of attention deficit hyperactivity disorder (ADHD), focusing on empiric research findings that connect genetic and environmental factors to structural and functional brain abnormalities, ultimately leading to a set of age-dependent behavioral manifestations. Section one presents evidence for genetic risk factors for ADHD and discusses the role of potential environmental factors in the etiology of the disorder. Section two focuses on brain imaging studies and how they have helped generate different hypotheses regarding the pathophysiology of ADHD. Finally, the article addresses the longitudinal course of symptoms in ADHD from infancy to adulthood in an attempt to place biological findings for this complex brain disorder in the context of maturation and development.

Aniracetam reversed learning and memory deficits following prenatal ethanol exposure by modulating functions of synaptic AMPA receptors

Specific pharmacological treatments are currently not available to address problems resulting from fetal ethanol exposure, described as Fetal Alcohol Syndrome or Fetal Alcohol Spectrum Disorders (FASD). The present study evaluated the therapeutic effects of aniracetam against cognitive deficits in a well-characterized and sensitive FASD Sprague-Dawley rat model. Ethanol, administered orally at a moderate dose (4 g/kg/24 h; 38% v/v) during the entire course of pregnancy, caused severe cognitive deficits in offspring. Furthermore, both progeny genders were affected by a spectrum of behavioral abnormalities, such as a delay in the development of the righting reflex, poor novelty seeking behavior, and high anxiety levels in female rats. Cognitive disabilities, monitored in adult rats by a two-way active avoidance task, correlated well with a significant reduction of AMPA (alpha-amino-3 hydro-5 methyl-isoxazole propionic acid) receptor-mediated miniature excitatory postsynaptic responses (mEPSCs) in the hippocampus. Administration of aniracetam for 10 days (post-natal days (PND) 18-27), at a dose of 50 mg/kg reversed cognitive deficits in both rat genders, indicated by a significant increase in the number of avoidances and the number of 'good learners'. After the termination of the nootropic treatment, a significant increase in both amplitude and frequency of AMPA receptor-mediated mEPSCs in hippocampal CA-1 pyramidal cells was observed. Significant anxiolytic effects on PND 40 also preceded acquisition improvements in the avoidance task. This study provides evidence for the therapeutic potential of aniracetam in reversing cognitive deficits associated with FASD through positive post-natal modulation of AMPA receptors.

On the development of nicotine dependence in adolescence

Little is known about the natural history of drug dependence. This article describes the development and predictors of DSM-IV nicotine dependence in adolescence when tobacco use is initiated. In a two-stage design, a survey was administered to 6th-10th graders in the Chicago Public Schools to select a cohort of adolescents. Household interviews were conducted with adolescents five times and with one parent (predominantly mothers) three times over 2 years. The analytical sample includes 353 youths, who started using tobacco within 12 months preceding Wave 1 or between Waves 1-5. Survival analysis estimated latency to individual DSM-IV nicotine dependence criteria and the full dependence syndrome. Twenty-five percent of youths experienced the syndrome within 23 months of tobacco use onset. Tolerance, impaired control and withdrawal were experienced most frequently. Youths who developed full dependence experienced their first symptom faster after tobacco use onset than those who experienced only one criterion through the end of the observation period. Cox proportional hazards models estimated the importance of time-constant and time-varying sociodemographic, tobacco and other drug use, parental and peer smoking, social psychological and biological risk factors for experiencing the first criterion and the full syndrome. Pleasant initial sensitivity to tobacco and number of cigarettes smoked the prior month predicted both outcomes. Parental dependence predicted the full syndrome. Significant covariates were generally the same across gender and racial/ethnic subgroups. The predictive significance of the initial smoking experience and parental dependence highlight the potential importance of genetic factors in the etiology of nicotine dependence.

Gestational exposure to nicotine and monoamine oxidase inhibitors influences cocaine-induced locomotion in adolescent rats

RATIONALE

Many pregnant women continue to smoke, despite a strong association between maternal smoking and neurobehavioral deficits in the offspring. Although gestational nicotine (GN) treatment in rodents is used as the primary animal model of maternal smoking, tobacco smoke contains more than 4,000 constituents, including monoamine oxidase inhibitors (MAOIs).

OBJECTIVES

The aim of this study was to determine whether there are interactions between the effects of gestational exposure to nicotine and MAOIs on cocaine-induced locomotor sensitization in adolescent rats.

MATERIALS AND METHODS

Pregnant rats were implanted on day 4 of gestation with osmotic minipumps delivering saline, nicotine (3 mg/kg per day), the MAOIs clorgyline and deprenyl (1 and 0.25 mg/kg per day, respectively), or nicotine/clorgyline/deprenyl (GMN). Adolescent female offspring were tested for cocaine-induced locomotor sensitization. Animals were treated with saline or cocaine (5 or 15 mg/kg, intraperitoneally) daily from postnatal (P) days 32-36 and challenged with cocaine (15 mg/kg) on P51 (day 20).

RESULTS

Group differences were observed in chronic but not acute effects of cocaine. Whereas gestational MAOI treatment, with or without nicotine, increased ambulatory response to cocaine on day 5, the opposite was found for vertical activity. Different adaptive responses were observed on cocaine challenge day. GNM animals exhibited enhanced locomotor activity in the cocaine-associated environment before cocaine challenge on day 20. In contrast, only GN animals exhibited significant locomotor sensitization to the cocaine challenge.

CONCLUSIONS

Gestational nicotine and MAOIs both influence brain development. Such interactions may sensitize adolescents to drug abuse and should be considered in animal models of maternal smoking.

Mobile Phone Radiation and the Developing Brain: Behavioral and Morphological Effects in Juvenile Rats

The increasing use of mobile phones by children and teenagers has raised concerns about their safety. Addressing such concerns is difficult, because no data are available on possible effects from long-term exposure to radiofrequency (RF) fields during the development of the nervous system. Possible morphological and functional changes were evaluated in the central nervous system of young male Wistar rats exposed to 900 MHz mobile phone signal for 2 h/day on 5 days/week. After 5 weeks of exposure at whole-body average specific energy absorption rates of 0.3 or 3.0 W/kg or sham exposure, six rats per group were examined histologically, and the remaining 18 rats per group were subjected to behavioral tests. No degenerative changes, dying neurons, or effects on the leakage of the blood-brain barrier were detected. No group differences were observed in the open-field test, plus maze test or acoustic startle response tests. In the water maze test, however, significantly improved learning (P = 0.012) and memory (P = 0.01) were detected in rats exposed to RF fields. The results do not indicate a serious threat to the developing brain from mobile phone radiation at intensities relevant to human exposure. However, the interesting finding of improved learning and memory warrants further studies.

Smoking during teenage pregnancies: effects on behavioral problems in offspring

We prospectively examined the relationship between prenatal tobacco exposure (PTE) and child behavior in a birth cohort of 357 offspring of teenage mothers. PTE was defined as any exposure across pregnancy and, in separate analyses, exposure within each trimester. Outcomes included measures of behavior problems, activity, and attention. On average, the children were 6.4 years of age, 48% were females, and 69% were Black. Data on maternal tobacco and other substance use were collected prenatally and postnatally: 46% of the mothers smoked in the first trimester and 58% smoked 6 years later. Child urinary cotinine measured exposure to environmental tobacco smoke (ETS). Stepwise multiple regressions were run. PTE predicted significantly increased offspring activity; impulsivity; and aggression, externalizing, and total behavior problems in step 1. PTE remained a significant predictor of increased activity when maternal psychological characteristics, home environment, and ETS were added. The results were similar when PTE was examined by trimesters, although later pregnancy tobacco exposure predicted the most behavioral outcomes. In the final model, PTE (all three trimesters) and PTE (second trimester) were significant predictors of increased activity and attention problems, respectively. Other predictors of child behavior included maternal anxiety, depression, hostility, and home environment. ETS was not a significant predictor of child behavior when PTE was considered. Smoking during pregnancy among adolescents is a significant predictor of increased activity and attention problems in their offspring after controlling for covariates in the prenatal and current environments. Smoking cessation interventions are recommended for this population to avoid the effects of PTE on the offspring of pregnant adolescents. This is particularly important because these mothers will likely become pregnant again and many will increase their level of tobacco use as they mature.

Combined exposure to nicotine and ethanol throughout full gestation results in enhanced acquisition of nicotine self-administration in young adult rat offspring

RATIONALE

Epidemiological evidence shows positive correlation between either maternal cigarette smoking or alcohol consumption on subsequent drug-taking behavior in offspring. However, the consequences of full gestational exposure to both drugs have not been studied experimentally despite concurrent use frequently reported among women of childbearing age. Such comorbid gestational drug exposure may increase susceptibility to acquiring cigarette smoking (i.e., nicotine self-administration), a major gateway drug.

OBJECTIVES

We developed a noninvasive rat model for exposure to both nicotine (2-6 mg kg(-1) day(-1)) and EtOH (4 g/kg gavage) that continued throughout pregnancy and postnatal (P) days 2-12, the rodent equivalent of the human third trimester, a critical brain developmental period. Offspring with this full gestational exposure to both drugs (Nic+EtOH) were compared to controls: nicotine alone, EtOH alone, pair-fed (comparable nutrition and handling), and ad libitum chow-fed. At P60-90, offspring had unlimited chronic access to acquire i.v. nicotine self-administration.

RESULTS

There were no differences in gender ratio, stillbirths, birth weights, righting reflex, eye opening age, or weight gain. However, Nic+EtOH offspring of both genders acquired nicotine self-administration (15 or 30 microg kg(-1) injection(-1)) more rapidly, at a higher percentage, and at a higher level than offspring in the other cohorts.

CONCLUSION

Full gestational Nic+EtOH exposure produced no overt alterations in standard postnatal measures but resulted in an enhanced acquisition of nicotine self-administration in young adult offspring.

Visuospatial working memory in school-aged children exposed in utero to cocaine

OBJECTIVE

Among the neurocognitive impairments reported as associated with prenatal cocaine exposure, slower response time, and less efficient learning in school-aged children are common to findings from several laboratories. This study presents performance data on a spatial working memory task in 75 prenatally cocaine exposed (CE) and 55 nondrug-exposed (NDE) 8- to 10-year-old children.

METHODS

Children were administered a novel neuropsychological measure of immediate- and short-term memory for visuospatial information, the Groton Maze Learning Test (GMLT), a computer-based hidden maze learning test that consists of a "timed chase test" (a simple measure of visuomotor speed), eight learning trials followed by a delayed recall trial after an 8-minute delay and a reverse learning trial. Performance is expressed as correct moves per second and number of errors per trial.

RESULTS

Across all trials, the cocaine-exposed group showed significantly slower correct moves per second and made significantly more errors. There were no significant main effects for amounts of alcohol, tobacco, or marijuana exposure. After an 8-minute delay and compared to the eighth trial, cocaine-exposed children showed less consolidation in learning compared to nonexposed children. When asked to complete the maze in reverse, cocaine-exposed children showed a greater decrement in performance (decreased correct moves per second and increased errors) compared to the eighth learning trial.

CONCLUSIONS

Children exposed in utero to cocaine exhibit a possible impairment in procedural learning and diminished efficiency in creating and accessing an internal spatial map to master the hidden maze.

Undertaking positive control studies as part of developmental neurotoxicity testing: a report from the ILSI Research Foundation/Risk Science Institute expert working group on neurodevelopmental endpoints

Developmental neurotoxicity testing involves functional and neurohistological assessments in offspring during and following maternal and/or neonatal exposure. Data from positive control studies are an integral component in developmental neurotoxicity risk assessments. Positive control data are crucial for evaluating a laboratory's capability to detect chemical-induced changes in measured endpoints. Positive control data are also valuable in a weight-of-evidence approach to help determine the biological significance of results and provide confidence in negative results from developmental neurotoxicity (DNT) studies. This review is a practical guide for the selection and use of positive control agents in developmental neurotoxicology. The advantages and disadvantages of various positive control agents are discussed for the endpoints in developmental neurotoxicity studies. Design issues specific to positive control studies in developmental neurotoxicity are considered and recommendations on how to interpret and report positive control data are made. Positive control studies should be conducted as an integral component of the incorporation and use of developmental neurotoxicity testing methods in laboratories that generate data used in risk decisions.

Genetic and pharmacological approaches to evaluate the interaction between the cannabinoid and cholinergic systems in cognitive processes

BACKGROUND AND PURPOSE

The objective of this study was to investigate the possible interactions between the cannabinoid and cholinergic systems in memory and learning processes by using genetic and pharmacological approaches in two different behavioural models, the active avoidance and the object recognition test.

EXPERIMENTAL APPROACH

The effects induced by nicotine, physostigmine and scopolamine were studied in CB(1) receptor knockout and wild-type mice in the active avoidance paradigm. In addition, the effects of pretreatment with the CB(1) receptor antagonist rimonabant were evaluated on the responses induced by nicotine in the active avoidance and the object recognition tasks in wild-type mice.

KEY RESULTS

Nicotine (0.5 mg kg(-1) s.c.) did not modify the performance of CB(1) knockout and wild-type mice in this model, whereas scopolamine (0.5 mgkg(-1) i.p.) impaired the performance in both genotypes. Physostigmine (0.1 mg kg(-1) i.p.) increased the active avoidance performance in wild-type but not in CB(1) knockout mice. Rimonabant (0.3, 1, 3, and 10 mg kg(-1)) did not modify the performance in the active avoidance test, given alone or co-administered with nicotine. In contrast, nicotine enhanced the performance in the object recognition task but this response was attenuated by rimonabant co-administration.

CONCLUSIONS AND IMPLICATIONS

The present findings revealed that the cognitive effects of nicotine and physostigmine were attenuated in the absence of CB(1) receptor activity. Scopolamine effects were independent from CB(1) receptors.

Guidelines on nicotine dose selection for in vivo research

RATIONALE

This review provides insight for the judicious selection of nicotine dose ranges and routes of administration for in vivo studies. The literature is replete with reports in which a dosaging regimen chosen for a specific nicotine-mediated response was suboptimal for the species used. In many cases, such discrepancies could be attributed to the complex variables comprising species-specific in vivo responses to acute or chronic nicotine exposure.

OBJECTIVES

This review capitalizes on the authors' collective decades of in vivo nicotine experimentation to clarify the issues and to identify the variables to be considered in choosing a dosaging regimen. Nicotine dose ranges tolerated by humans and their animal models provide guidelines for experiments intended to extrapolate to human tobacco exposure through cigarette smoking or nicotine replacement therapies. Just as important are the nicotine dosaging regimens used to provide a mechanistic framework for acquisition of drug-taking behavior, dependence, tolerance, or withdrawal in animal models.

RESULTS

Seven species are addressed: humans, nonhuman primates, rats, mice, Drosophila, Caenorhabditis elegans, and zebrafish. After an overview on nicotine metabolism, each section focuses on an individual species, addressing issues related to genetic background, age, acute vs chronic exposure, route of administration, and behavioral responses.

CONCLUSIONS

The selected examples of successful dosaging ranges are provided, while emphasizing the necessity of empirically determined dose-response relationships based on the precise parameters and conditions inherent to a specific hypothesis. This review provides a new, experimentally based compilation of species-specific dose selection for studies on the in vivo effects of nicotine.

Effects of maternal intravenous nicotine administration on locomotor behavior in pre-weanling rats

Maternal tobacco use is associated with adverse developmental outcomes in offspring, including hyperactivity. Animal studies attempting to model this phenomenon have primarily used continuous s.c. nicotine infusion as the method of nicotine administration, which does not model the intermittent bolus delivery of nicotine associated with smoking in humans. The purpose of the present experiment was to examine the locomotor activity of pre-weanling offspring of pregnant rats exposed to an i.v. nicotine dosing protocol that approximates the pattern of nicotine exposure in moderate to heavy smokers. Pregnant rats were administered an i.v. bolus of 0.03 mg/kg nicotine (N=13) or saline (N=10) every 14 min for 16 h/day, resulting in a total daily dose of 2 mg/kg (base), from gestational day 4 to delivery. Pups from each litter were tested for spontaneous locomotor activity on postnatal days (PND) 19-21 and nicotine-induced locomotor activity on PND 22. Mean birth weight was significantly lower in nicotine-exposed pups compared to controls, but body weights were equivalent between groups by the time of behavioral testing. Mean total distance traveled, vertical counts, and stereotypy counts were lower on PND 19 in nicotine-exposed pups compared to controls, but only the difference in mean stereotypy counts was statistically significant. Within-session analysis revealed that both distance traveled and stereotypy were significantly decreased in nicotine-exposed pups in the first 5 min of the session on PND 19. Total time spent in the center of the field was also lower in nicotine-exposed pups. Nicotine-induced increases in activity on PND 22 did not differ according to gestational exposure. These findings demonstrate that prenatal nicotine exposure in a model that mimics the pattern of nicotine exposure from cigarette smoking in humans results in offspring that exhibit low birth weight and hypoactivity in a novel environment.

Perinatal nicotine exposure eliminates peak in nicotinic acetylcholine receptor response in adolescent rats

Maternal smoking is a risk factor associated with nicotine abuse, so the effect of perinatal nicotine exposure was studied on the responsiveness to nicotine across adolescence in the rat. Pregnant Sprague-Dawley rats were implanted with s.c. Alzet osmotic minipumps delivering nicotine (L-nicotine hydrogen tartrate, 2 mg/kg/day free base) or vehicle (0.9% saline) on gestational day 7. There was no effect of nicotine on dam weight gain, food consumption, or water consumption or on the number of live pups or weights at the time of birth. Pups were cross-fostered to obtain the following prenatal/postnatal exposure groups: control/control, nicotine/nicotine, nicotine/control, and control/nicotine. On postnatal days 28, 35, 49, and 63, nicotine-stimulated (86)Rb(+) efflux was measured in synaptosomes prepared from the frontal cortex, hippocampus, striatum (STR), and thalamus (THL), using a previously developed method. Significant effects of treatment and concentration were detected in all four brain regions, and significant effects of age were observed in the STR and THL. Significant interactions of age and treatment were observed in each of the four brain regions. Nicotine-stimulated (86)Rb(+) efflux peaked during adolescence in control rats. However, perinatal exposure to nicotine eliminated this peak during adolescence. These results are consistent with recent behavioral and receptor binding results from other laboratories and are the first direct evidence at the cellular level that the nicotinic acetylcholine receptor response varies during adolescence and is affected by perinatal nicotine exposure.

Effects of nicotine exposure during prenatal or perinatal period on cell numbers in adult rat hippocampus and cerebellum: a stereology study

Smoking during pregnancy poses a potential risk to unborn children. The present study examined the long-term effects of early nicotine exposure on the number of pyramidal and granule cells in the hippocampus, and Purkinje cells in the cerebellar vermis. The loss of neurons is the most severe form of brain injury with significant functional implications. In this study, rats were exposed to nicotine during either the prenatal (PRE) period or both the prenatal and early postnatal (PERI) period. It was hypothesized that nicotine treatment would result in long-term decreases in neuronal numbers, and that PERI treatment would be more detrimental to these cell populations than the PRE treatment. The results showed that neither PRE nor PERI nicotine exposure reduces the numbers of pyramidal, granule or Purkinje cells. Neither the regions where these cells reside, nor the cell densities were affected by nicotine. Although no significant cell loss was observed, the current nicotine exposure regimens may lead to alterations in cellular functions or cytoarchitectures. The present results in conjunction with previous reports showing significant cell loss from nicotine exposure during the brain growth spurt suggest that "patch-like" nicotine exposure during prenatal period may alter the sensitivity or the responsiveness of the developing brain to the injurious effects of nicotine during the most vulnerable stage of brain development - the brain growth spurt. Furthermore, the current stereology cell counting results are not in agreement with some reports in the literature, and this discrepancy may simply be a function of different cell counting techniques used.

Gestational nicotine-induced changes in adolescent neuronal activity

Smoking during pregnancy is associated with numerous physiological and neurobehavioral deficits in infants, which persist into adolescence. To better understand the underlying mechanisms, we have treated pregnant rats with nicotine and have evaluated expression of the immediate early gene c-fos, as a measure of neuronal activity, in the brains of adolescent male offspring. Pregnant dams were infused with nicotine (3 mg/kg/day) or saline from gestational day (G) 4 until G18. After birth on G22, litters were cross fostered and weaned at postnatal day (P) 21. Brain sections from adolescent offspring, aged P38-40, were analyzed by in situ hybridization for regional c-fos mRNA expression in response to acute injection of saline or nicotine (0.03, 0.1, 0.3 mg/kg). Acute nicotine challenge increased c-fos expression within nucleus accumbens shell, lateral bed nucleus of the stria terminalis, paraventricular nucleus of the hypothalamus, dorsal lateral geniculate, and superior colliculus, whereas c-fos expression was decreased in prelimbic cortex. There was no effect of gestational nicotine treatment on acute nicotine-induced alterations in c-fos mRNA levels. However, basal c-fos mRNA expression within infralimbic cortex and nucleus accumbens core was increased by gestational nicotine treatment. These data indicate that gestational nicotine does not produce global changes in nicotine-induced c-fos expression in adolescent brain. However, gestational drug exposure changes basal neuronal activity within mesocorticolimbic structures that are critical for motivated behavior. Such changes may underlie some of the behavioral deficits in attention, cognition, and impulse control that have been reported in the offspring of smoking mothers.

Exposure of mothers to diphenyl ditelluride during the suckling period changes behavioral tendencies in their offspring

The long-lasting possible influence of maternal exposure to 0.03 mg/kg of diphenyl ditelluride during the first 14 days of lactational period on later offspring behavior was examined in Wistar rats. Open-field locomotor activity, spontaneous alternation in the T-maze, behavior in the elevated plus-maze, motor coordination in the coat-hanger and rotorod tasks were evaluated in 30 day old pups. There were no significant specific overt signs of maternal intoxication. There were a small (less than 5%) but significant transitory differences in the body weight gain of pups between exposed and control groups, which were apparent from day 30 of suckling. Locomotor activity in the open-field task was similar between telluride and control groups. In the coat-hanger test, the latency before falling for the tellurium group was higher than that of the control group. However, the behavior of both groups was similar in the rotorod test and spontaneous alternation in the T-maze. Tellurium-treated pups presented a higher number of entries and spent more time in the open arms of the elevated plus-maze than control pups. The behavioral alterations observed here after tellurium exposure can be cautiously interpreted as an indication of behavioral disinhibition. In conclusion, this study demonstrated that dam exposure to diphenyl ditelluride can cause subtle behavioral changes in the offspring, which can be related to neurotoxic effects of diphenyl ditelluride.

alpha7 Nicotinic acetylcholine receptors and temporal memory: synergistic effects of combining prenatal choline and nicotine on reinforcement-induced resetting of an interval clock

We previously showed that prenatal choline supplementation could increase the precision of timing and temporal memory and facilitate simultaneous temporal processing in mature and aged rats. In the present study, we investigated the ability of adult rats to selectively control the reinforcement-induced resetting of an internal clock as a function of prenatal drug treatments designed to affect the alpha7 nicotinic acetylcholine receptor (alpha7 nAChR). Male Sprague-Dawley rats were exposed to prenatal choline (CHO), nicotine (NIC), methyllycaconitine (MLA), choline + nicotine (CHO + NIC), choline + nicotine + methyllycaconitine (CHO + NIC + MLA), or a control treatment (CON). Beginning at 4-mo-of-age, rats were trained on a peak-interval timing procedure in which food was available at 10-, 30-, and 90-sec criterion durations. At steady-state performance there were no differences in timing accuracy, precision, or resetting among the CON, MLA, and CHO + NIC + MLA treatments. It was observed that the CHO and NIC treatments produced a small, but significant increase in timing precision, but no change in accuracy or resetting. In contrast, the CHO + NIC prenatal treatment produced a dramatic increase in timing precision and selective control of the resetting mechanism with no change in overall timing accuracy. The synergistic effect of combining prenatal CHO and NIC treatments suggests an organizational change in alpha7 nAChR function that is dependent upon a combination of selective and nonselective nAChR stimulation during early development.

In utero exposure to nicotine and chlorpyrifos alone, and in combination produces persistent sensorimotor deficits and Purkinje neuron loss in the cerebellum of adult offspring rats

This study was carried out to investigate the effect of in utero exposure to the cholinotoxicants, nicotine and chlorpyrifos, alone or in combination on neurobehavioral alterations and neuronal morphology latter in adult age. In the present study, 90 days old (corresponding to a human adult age) male and female offspring rats were evaluated for neurobehavioral, and neuropathological alterations following maternal, gestational exposure to nicotine and chlorpyrifos (O,O-diethyl-O-3,5,6-trichloro-2-pyridinyl phosphorothioate), alone and in combination. Female Sprague-Dawley rats (300-350 g) with timed-pregnancy were treated with nicotine (3.3 mg/kg/day, in bacteriostatic water via s.c. implantation of mini osmotic pump), chlorpyrifos (1.0 mg/kg, daily, dermal, in 75% ethanol, 1.0 ml/kg) or a combination of both chemicals, on gestational days (GD) 4-20. Control animals received bacteriostatic water via s.c. implantation of mini osmotic pump and dermal application of 70% ethanol. The offspring at postnatal day (PND) 90 were evaluated for neurobehavioral performance, changes in the activity of plasma butyrylcholinesterase (BChE) and acetylcholinesterase (AChE), and neuropathological alterations in the brain. Neurobehavioral evaluations included beam-walk score, beam-walk time, incline plane performance and forepaw grip time. Male and female offspring from mothers treated with nicotine and CPF, alone or in combination showed impairments in the performance of neurobehavioral tests, indicating sensorimotor deficits. Female offspring from mothers treated with a combination of nicotine and chlorpyrifos showed significant increase in plasma BChE activity. Brain regional AChE activity showed differential increases in male and female offspring. Brainstem and cerebellum of female offspring from mothers treated with nicotine or chlorpyrifos, alone or in combination showed increased AChE activity, whereas brainstem of male offspring from mothers treated with nicotine alone or a combination of nicotine and chlorpyrifos showed increase in AChE activity. Also, male offspring exposed in utero to nicotine exhibited increased AChE activity. Histopathological evaluations using cresyl violet staining showed a decrease in surviving Purkinje neurons in the cerebellum in offspring of all treatments groups. An increase in glial fibrillary acidic protein (GFAP) immuno-staining was observed in cerebellum white matter as well as granular cell layer (GCL) of cerebellum following all exposures. These results indicate that in utero exposure to nicotine and chlorpyrifos, alone and in combination produced significant sensorimotor deficits in male and female offspring, differential increase in brain AChE activity, a decrease in the surviving neurons and an increased expression of GFAP in cerebellum in adult offspring rats at a corresponding human adult age. Collectively, this study demonstrates that maternal exposure to environmental neurotoxic chemicals, i.e., nicotine and chlorpyrifos leads to developmental abnormalities in the offspring that persist latter into adulthood.

Effects of housing and nicotine on shuttle-box avoidance in male NMRI mice

The present study aimed to evaluate whether housing condition could interact with nicotine administration in influencing the acquisition of a two-way active avoidance task. Male NMRI mice were either group- or individually housed for 30 days and, after this period, evaluated both in the actimeter and, 24h later, in the elevated plus-maze. On the basis of the percentage of time spent in the open arms of the plus-maze, both group- and individually housed mice were sub-classified into three groups with high, moderate or low anxiety baseline levels. Effects of nicotine on the acquisition of the two-way active avoidance task was assessed in each of these groups of mice using an automated shuttle-box. Mice were treated with nicotine (0.35 mg/kg) or vehicle before each daily training session in the shuttle-box (30 trials) over 5 days. The results showed that motor activity counts were significantly higher in individually housed mice than in group-housed counterparts. The factor "anxiety" in the active avoidance test did not reach statistical significance but the factor "housing" did. The number of avoidances was higher in individually housed than in group-housed mice. Separate analyses performed for individually and group-housed animals indicated that group-housed nicotine-treated mice displayed fewer number of avoidances than saline-treated counterparts. It was concluded that housing condition may be a useful variable in evaluating the effects of nicotine on learning tasks. Indeed, the two-way active avoidance task seems to be sensitive to housing condition.

Individual differences in novelty-seeking behavior but not in anxiety response to a new environment can predict nicotine consumption in adolescent C57BL/6 mice

Considering that adolescence is associated with an increased motivation to seek out new stimuli and with low anxiety levels in exploring novel environments, and that both behavioral traits may be associated with substance abuse, we investigated whether the behavioral response to a novel environment can predict subsequent oral nicotine self-administration in adolescent C57BL/6 mice. On postnatal day 30 (PN30), the novelty-seeking behavior and anxiety levels were assessed in a hole board activity box. The total number of head-dips (DIP) was used to classify animals either into the high novelty (HN; DIP above median) or low novelty (LN; DIP below median) groups. The percentage of center squares crossed (CEN) was used to classify animals either into the high anxiety (HA; CEN below median) or low anxiety (LA; CEN above median) groups. From PN31 to PN41, all animals were given a free choice between tap water or a nicotine solution (10 microg/ml). LN mice did not change nicotine intake throughout the free choice procedure, however, HN mice presented a marked increase in consumption. There were no differences in consumption between HA and LA mice. Our results indicated that mice that presented a more intense novelty-seeking behavior increased their preference for nicotine during the free choice experiment but that anxiety levels did not predict nicotine consumption. These results suggest that higher motivation to seek out new experiences is a significant contributor to drug use in adolescents and that anxiety is probably not a major factor that determines differential nicotine consumption during adolescence.

Chronic nicotine induces growth retardation in neonatal rat pups

In the United State, 20% of pregnant women smoke. One of the most consistent adverse outcomes is reduced birth weight in the off-spring. Animal studies using chronic nicotine, the major psychoactive tobacco ingredient, have shown conflicting results, questioning the role of nicotine in growth retardation. To evaluate the direct effects of nicotine during a period equivalent to the human third trimester, we developed an oral gastric intubation model using neonatal rat pups. Nicotine (6 mg/kg/day) was dissolve in milk-formula and delivered during three feedings daily from postnatal day (P)1 to P7. Nicotine immediately and significantly [P<0.05] decreased weight gain per day (WGD) by 13.5% (+/-) 1 day after onset of treatment in both genders and throughout the treatment period. This resulted in significantly lower body weight at P4 and P5 in male and female pups, respectively. After nicotine withdrawal, WGD returned to control level within 1 day, whereas total body weight recovered by P18. There were no long-term consequences on body weight or growth pattern in either gender. The nicotinic acetylcholine receptor (nAChR) antagonist dihydro-beta-erythroidine (DHbetaE) reversed nicotine's effects on WGD suggesting an involvement of heteromeric alpha4beta2, whereas methyllycaconitine (MLA) an antagonist for the homomeric alpha7-type receptor was ineffective. The immediate decrease of growth in neonatal pups suggests that nicotine's effect on birth weight results from direct anorexic rather then indirect effects due to placental dysfunction or increased fetal hypoxia. The postnatal oral gastric intubation model seems to accurately reflect the direct effects of nicotine in neonates.

Event-related potentials in cocaine-exposed children during a Stroop task

OBJECTIVE

Prenatal cocaine-exposure may interfere with the ontogeny of prefrontal cortical executive functions due to cocaine's effect on the developing monoaminergic system. This study presents findings regarding cortical functioning in 29 prenatally cocaine-exposed (CE) and non-drug-exposed (NDE) 7- to 9-year-old children participating in event related potential (ERP) studies.

METHODS

ERPs were recorded using 128-electrode high-density arrays while children responded to a standard Stroop paradigm.

RESULTS

In the Stroop paradigm, CE children generated prolonged responses to the words while the NDE children produced briefer responses. Effects were noted in the region of the initial positive peak (P1), the second negative peak (N2) and the later positive peak (P3).

CONCLUSIONS

Early cocaine exposure may inhibit the specialization and streamlining of brain region involvement during cognitive processing such that task processing is slower to begin, requires more diverse cortical involvement, and requires more time to complete. ERP methodology has considerable potential for studying frontal maturation and may provide additional information to clarify generally the specific effects of prenatal CE on cortical functioning and the developmental course of cognitive functions.

Bupropion effects on aggressiveness and anxiety in OF1 male mice

RATIONALE

Bupropion is an antidepressant drug that is being used to help in giving up smoking. Its behavioral effects have been evaluated in different animal models, although limited information is available regarding its effects on aggressiveness, anxiety and exploratory behavior.

OBJECTIVES

Evaluate acute effects of bupropion on locomotor activity, isolation-induced aggression, hole-board and elevated plus-maze tests in OF1 male mice.

METHODS

In the first experiment, effects of bupropion (2.5, 5, 10, 20 and 40 mg/kg) on locomotion were evaluated. In the second experiment, isolation-induced aggression was assessed in isolated male mice previously classified as short attack latency (SL) and long attack latency (LL). Mice were treated with bupropion or vehicle and confronted with standard opponents for 10 min. In experiments 3 and 4, mice were treated with bupropion or vehicle and 30 min later examined in the plus-maze or in the hole-board apparatus.

RESULTS

In the actimeter, bupropion induced a dose-dependent increase in locomotion. During agonistic encounters, bupropion (10 mg/kg and 40 mg/kg) increased time devoted to attack in LL mice. In the plus-maze, no significant differences were found between bupropion-treated and vehicle-treated mice in the percentage of entries or time spent in open arms. In the hole-board, the highest dose of bupropion (40 mg/kg) significantly decreased number of head-dips and increased latency to the first head-dip.

CONCLUSIONS

During agonistic encounters the two sub-groups of mice (SL and LL) may display differential sensitivity in drug-induced changes on aggressiveness, since bupropion increased attack only in mice with "long attack latency" in the pre-screening test. In the plus-maze, this drug does not seem to have specific actions on anxiety and in the hole-board a high dose had similar effects to those induced by anxiogenic drugs.

Effect of prenatal or perinatal nicotine exposure on neonatal thyroid status and offspring growth in rats

Smoking during pregnancy causes intrauterine growth retardation and low birth weight of the offspring. However, it is unclear whether nicotine, rather than other compounds from a cigarette, would mediate long-term growth retardation. There is a body of evidence suggesting that optimal thyroid status is important for the normal development of the fetus. Therefore, these studies examined whether developmental nicotine exposure would interfere with the growth of the offspring and alter the thyroid status of neonates. Pregnant Sprague-Dawley rats were given 0, 15 or 25 mg nicotine pellets throughout pregnancy. Some offspring continued to receive 1 or 2 mg/kg/day nicotine during early postnatal period. The remaining offspring received no further treatment after birth. The body weight of all offspring was monitored until adulthood. Additionally, the neonatal thyroid status from all treatment groups was assessed from the serum of 10-day-old pups. Regardless of the timing of nicotine exposure, the nicotine treatment significantly increased the body weight in female offspring starting on postnatal day (PD) 35 and such an increase persisted into adulthood (PD 91). However, this nicotine exposure paradigm led to a transient increase in male offspring body weight on PD 35. Furthermore, current nicotine exposure regimens did not alter the total T4 level, T3 uptake and the calculated Free T4 index. The present findings are in agreement with some clinical studies reporting a higher body weight among children born to mothers who smoked during pregnancy. Furthermore, the data on thyroid status suggest that cigarette smoking-induced alterations in thyroid status might be mediated through compounds in cigarettes other than nicotine.