Prenatal nicotine exposure alters the response to nicotine administration in adolescence: effects on cholinergic systems during exposure and withdrawal

Prenatal exposure of rats to nicotine causes persistent alterations of nicotinic cholinergic receptors

We examined for immediate and persistent changes in nAChRs in cerebral cortex, thalamus and striatum of male rats caused by prenatal exposure to nicotine from gestational day 3 to postnatal day 10 (PN10), and how such exposure affected the responses of adolescents to subsequent nicotine challenge. Receptor numbers were assessed by [(3)H]epibatidine binding and receptor function was measured by acetylcholine-stimulated (86)Rb efflux (cerebral cortex and thalamus) and nicotine-stimulated dopamine release (striatum). Immediate effects of prenatal nicotine, assessed in PN10 animals, were not detected for any parameter. A subsequent 14 day nicotine exposure in adolescence revealed persistent changes caused by prenatal nicotine exposure. Nicotine exposure in adolescents caused up-regulation of binding in all three regions; however, this up-regulation was lost in thalamus from animals prenatally exposed to nicotine. Nicotine exposure in adolescents caused decreased nicotine-stimulated dopamine release in striatum; this effect was lost in animals prenatally exposed to nicotine. Comparison of parameters in PN10 and PN42 rats revealed developmental changes in the CNS cholinergic system. In thalamus, binding increased with age, as did the proportion of (86)Rb efflux with high sensitivity to acetylcholine. In cortex, binding also increased with age, but there was no change in total (86)Rb efflux, and the proportion of high to low sensitivity efflux declined with age. Nicotine-stimulated striatal dopamine release (both total and alpha-conotoxin MII-resistant release) increased with age in naïve animals, but not in those prenatally exposed to nicotine. These findings demonstrate that prenatal exposure to nicotine causes alterations in nAChRs and in their regulation by nicotine that persist into adolescence. These changes may play a role in the increased risk for nicotine addiction observed in adolescent offspring of smoking mothers.

Neonatal nicotine exposure impairs development of auditory temporal processing

Accurate temporal processing of sound is essential for detecting word structures in speech. Maternal smoking affects speech processing in newborns and may influence child language development; however, it is unclear how neonatal exposure to nicotine, present in cigarettes, affects the normal development of temporal processing. The present study used the gap-induced prepulse inhibition (gap-PPI) of the acoustic startle response to investigate the effects of neonatal nicotine exposure on the normal development of gap detection, a behavioral testing procedure of auditory temporal resolution. Neonatal rats were injected twice per day with saline (control), 1mg/kg nicotine (N-1 mg) or 5 mg/kg nicotine (N-5 mg) from postnatal day 8-12 (P8-P12). During the first month after birth, rats showed poor gap-PPI in all three groups. At P45 and P60, gap-PPI in control rats improved significantly, whereas rats exposed to nicotine exhibited less improvement. At P60, the gap-detection threshold in the N-5 mg group was significantly higher than in the control group, suggesting that neonatal nicotine exposure affects the normal development of gap-detection acuity. Additionally, 1h after receiving an acute nicotine injection (1 mg/kg), gap-PPI recorded in adult rats from the N-5 mg group showed a temporary significant improvement. These results suggest that neonatal nicotine exposure reduces gap-PPI implying an impairment of the normal development of auditory temporal processing by inducing changes in cholinergic systems.

If nicotine is a developmental neurotoxicant in animal studies, dare we recommend nicotine replacement therapy in pregnant women and adolescents?

Tobacco use in pregnancy is a leading cause of perinatal morbidity and contributes in major ways to attention deficit hyperactivity disorder, conduct disorders and learning disabilities that emerge in childhood and adolescence. Over the past two decades, animal models of prenatal nicotine exposure have demonstrated that nicotine is a neurobehavioral teratogen that disrupts brain development by preempting the natural, neurotrophic roles of acetylcholine. Through its actions on nicotinic cholinergic receptors, nicotine elicits abnormalities of neural cell proliferation and differentiation, promotes apoptosis and produces deficits in the number of neural cells and in synaptic function. The effects eventually compromise multiple neurotransmitter systems because of the widespread regulatory role of cholinergic neurotransmission. Importantly, the long-term alterations include effects on reward systems that reinforce the subsequent susceptibility to nicotine addiction in later life. These considerations strongly question the appropriateness of nicotine replacement therapy (NRT) for smoking cessation in pregnant women, especially as the pharmacokinetics of the transdermal patch may actually enhance fetal nicotine exposure. Further, because brain maturation continues into adolescence, the period when smoking typically commences, adolescence is also a vulnerable period in which nicotine can change the trajectory of neurodevelopment. There are also serious questions as to whether NRT is actually effective as an aid to smoking cessation in pregnant women and adolescents. This review considers the ramifications of the basic science findings of nicotine's effects on brain development for NRT in these populations.

Adolescent nicotine administration changes the responses to nicotine given subsequently in adulthood: adenylyl cyclase cell signaling in brain regions during nicotine administration and withdrawal, and lasting effects

Neurodevelopmental vulnerability to nicotine extends into adolescence, the stage at which most smokers begin using tobacco. The "sensitization-homeostasis" model postulates that nicotine treatment permanently reprogrammes neural communication, so that underlying functional changes remain present despite the apparent restoration of behavioral normality. We administered nicotine to adolescent rats (postnatal days PN30-47) or adults (postnatal days PN90-107), using regimens that reproduce plasma levels in smokers, and assessed effects on the adenylyl cyclase (AC) signaling cascade, which is involved in nicotine dependence and withdrawal but also mediates numerous other neurotransmitter responses. Evaluations were made in the cerebral cortex, brainstem and cerebellum on PN105, PN110, PN120, PN130 and PN180. Adolescent nicotine exposure elicited persistent suppression of basal AC activity and eventual compromise of responses to beta-adrenergic receptor stimulation, with effects emerging in late adulthood; maximal AC activity as monitored with forskolin was elevated and in general, all the effects were more notable in males. Nicotine treatment in adulthood produced an immediate increase in AC activity in males that disappeared upon withdrawal; there were late-emerging deficits similar to, but smaller in magnitude than those seen with adolescent nicotine exposure. Adolescent treatment greatly exacerbated the response to subsequent nicotine administration in adulthood, producing profound AC deficits during withdrawal that persisted through at least 6 months of age. Our results reinforce the concept that adolescence is a critical developmental period in which nicotine disrupts neural cell signaling in a lasting manner, and provide a mechanistic framework for understanding the biological substrates that determine the relationship between adolescent nicotine exposure and life-long susceptibility to nicotine addiction.

Combined exposure to nicotine and ethanol in adolescent mice differentially affects anxiety levels during exposure, short-term, and long-term withdrawal

Smoking and consumption of alcoholic beverages are frequently associated during adolescence. This association could be explained by the cumulative behavioral effects of nicotine and ethanol, particularly those related to anxiety levels. However, despite epidemiological findings, there have been few animal studies of the basic neurobiology of the combined exposure in the adolescent brain. In the present work we assessed, through the use of the elevated plus maze, the short- and long-term anxiety effects of nicotine (NIC) and/or ethanol (ETOH) exposure during adolescence (from the 30th to the 45th postnatal day) in four groups of male and female C57BL/6 mice: (1) Concomitant NIC (nicotine free-base solution (50 microg/ml) in 2% saccharin to drink) and ETOH (ethanol solution (25%, 2 g/kg) i.p. injected every other day) exposure; (2) NIC exposure; (3) ETOH exposure; (4) Vehicle. C57BL/6 mice were selected, in spite of the fact that they present slower ethanol metabolism, because they readily consume nicotine in the concentration used in the present study. During exposure (45th postnatal day: PN45), our results indicated that ethanol was anxiolytic in adolescent mice and that nicotine reverted this effect. Short-term drug withdrawal (PN50) elicited sex-dependent effects: exposure to nicotine and/or ethanol was anxiogenic only for females. Although neither nicotine nor ethanol effects persisted up to 1 month postexposure (PN75), the coadministration elicited an anxiogenic response. In spite of the fact that generalizations based on the results from a single strain of mice are prone to shortcomings, our results suggest that the deficient response to the anxiolytic effects of ethanol in adolescents co-exposed to nicotine may drive higher ethanol consumption. Additionally, increased anxiety during long-term smoking and drinking withdrawal may facilitate relapse to drug use.

Adolescent nicotine treatment changes the response of acetylcholine systems to subsequent nicotine administration in adulthood

Nicotine alters the developmental trajectory of acetylcholine (ACh) systems in the immature brain, with vulnerability extending from fetal stages through adolescence. We administered nicotine to adolescent rats (postnatal days PN30-47) and then examined the subsequent response to nicotine given in adulthood (PN90-107), simulating plasma levels in smokers, and performing evaluations during nicotine treatment (PN105) and withdrawal (PN110, PN120 and PN130), as well as assessing persistent changes at 6 months of age (PN180). We measured nicotinic acetylcholine receptor (nAChR) binding, choline acetyltransferase (ChAT) activity, a marker for ACh terminals, and hemicholinium-3 (HC3) binding to the choline transporter, an index of ACh presynaptic activity. By itself, adolescent nicotine exposure evoked sex-selective deficits in cerebrocortical HC3 binding while elevating ChAT in young adulthood in striatum and midbrain. Nicotine given in adulthood produced profound nAChR upregulation lasting 2 weeks after discontinuing treatment, and decrements in cerebrocortical and striatal HC3 binding emerged during withdrawal, indicative of reduced ACh synaptic activity. For all three parameters, adolescent nicotine altered the responses to nicotine given in adulthood, producing both sensitization and desensitization that depended on sex and brain region, effects that parallel the disparate behavioral outcomes reported for these treatments. The interaction seen here for the impact of adolescent nicotine exposure on adult nicotine responses was substantially greater than that found previously for the effects of prenatal nicotine exposure on adult responses. Our findings thus reinforce the importance of adolescence as a critical period in which the future responsiveness to nicotine is programmed.

Smoking behavior in asthmatic and non-asthmatic adolescents: the role of smoking models and personality

Despite the particular health risks for asthmatics, recent international studies have reported that tobacco use among asthmatics is similar to, or even higher than, non-asthmatics. This study examined the role of personality and environment in smoking among asthmatic and non-asthmatic adolescents. In 2003 a random sample of 33 schools (first and second class of secondary education) was obtained in The Netherlands (N = 4,951). The mean age of the participants was 12.83 (SD = .75), and 52.8% were females. Information about asthma, smoking, personality, and environmental smoking was assessed via self-reports on standard epidemiology survey items (asthma, smoking) and the Quick Big Five (personality). Both personality and environmental smoking were associated with smoking. Asthmatics were similarly or even more exposed to environmental smoke than non-asthmatic adolescents and asthmatic adolescents were less emotionally stable and extravert. Associations between personality and own smoking behavior, as well as between smoking models and own smoking behavior were similar for asthmatic and non-asthmatics. Limitations of the study are taken notice of, and implications of the results are briefly discussed.

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.

Separate or sequential exposure to nicotine prenatally and in adulthood: Persistent effects on acetylcholine systems in rat brain regions

Nicotine is a developmental neurotoxicant but the proposed "sensitization-homeostasis" model postulates that even in adulthood nicotine permanently reprograms synaptic function. We administered nicotine to rats throughout gestation or in adulthood (postnatal days PN90-107), simulating plasma levels in smokers, with evaluations on PN105, PN110, PN120, PN130 and PN180. We assessed nicotinic acetylcholine receptor (nAChR) binding, choline acetyltransferase activity, a marker for acetylcholine (ACh) terminals, and hemicholinium-3 (HC3) binding to the choline transporter, an index of ACh presynaptic activity. Prenatal nicotine exposure elicited persistent deficits in HC3 binding in male cerebral cortex and female striatum, but little change in other parameters. Nicotine given in adulthood produced profound nAChR upregulation lasting 2 weeks after discontinuing treatment. Decrements in cerebrocortical and striatal HC3 binding emerged during withdrawal and persisted through PN180, indicative of reduced ACh synaptic activity. Prenatal nicotine did not evoke any major alterations in the response to nicotine given in adulthood. The effects seen here are substantially different from those found previously for nicotine given to adolescent rats, which showed more prolonged nAChR upregulation and profound, widespread and persistent deficits in markers of ACh synaptic function; for adolescents, prenatal nicotine exposure desensitized nAChR responses, exacerbated withdrawal-induced ACh functional deficits, and worsened the long-term outcome. Our results indicate that the effects of nicotine during prenatal or adolescent stages are indeed distinct from the effects in adults, but that even adults show persistent changes after nicotine exposure, commensurate with the sensitization-homeostasis model. These effects may contribute to lifelong vulnerability to readdiction.

Permanent, sex-selective effects of prenatal or adolescent nicotine exposure, separately or sequentially, in rat brain regions: indices of cholinergic and serotonergic synaptic function, cell signaling, and neural cell number and size at 6 months of age

Nicotine is a neuroteratogen that disrupts neurodevelopment and synaptic function, with vulnerability extending into adolescence. We assessed the permanence of effects in rats on indices of neural cell number and size, and on acetylcholine and serotonin (5HT) systems, conducting assessments at 6 months of age, after prenatal nicotine exposure, adolescent exposure, or sequential exposure in both periods. For prenatal nicotine, indices of cell number and size showed few abnormalities by 6 months, but there were persistent deficits in cerebrocortical choline acetyltransferase activity and hemicholinium-3 binding to the presynaptic choline transporter, a pattern consistent with cholinergic hypoactivity; these effects were more prominent in males than females. The expression of 5HT receptors also showed permanent effects in males, with suppression of the 5HT(1A) subtype and upregulation of 5HT(2) receptors. In addition, cell signaling through adenylyl cyclase showed heterologous uncoupling of neurotransmitter responses. Nicotine exposure in adolescence produced lasting effects that were similar to those of prenatal nicotine. However, when animals were exposed to prenatal nicotine and received nicotine subsequently in adolescence, the adverse effects then extended to females, whereas the net effect in males was similar to that of prenatal nicotine by itself. Our results indicate that prenatal or adolescent nicotine exposure evoke permanent changes in synaptic function that transcend the recovery of less-sensitive indices of structural damage; further, prenatal exposure sensitizes females to the subsequent adverse effects of adolescent nicotine, thus creating a population that may be especially vulnerable to the lasting behavioral consequences of nicotine intake in adolescence.

Critical review: nicotine for the fetus, the infant and the adolescent?

The recent expansion of Nicotine Replacement Therapy to pregnant women and children ignores the fact that nicotine impairs, disrupts, duplicates and/or interacts with essential physiological functions and is involved in tobacco-related carcinogenesis. The main concerns in the present context are its fetotoxicity and neuroteratogenicity that can cause cognitive, affective and behavioral disorders in children born to mothers exposed to nicotine during pregnancy, and the detrimental effects of nicotine on the growing organism. Hence, the use of nicotine, whose efficacy in treating nicotine addiction is controversial even in adults, must be strictly avoided in pregnancy, breastfeeding, childhood and adolescence.

Lasting effects of nicotine treatment and withdrawal on serotonergic systems and cell signaling in rat brain regions: separate or sequential exposure during fetal development and adulthood

Neurodevelopmental vulnerability to nicotine extends from fetal stages through adolescence. The recently proposed "sensitization-homeostasis" model postulates that, even in adulthood, nicotine treatment permanently reprograms synaptic activity. We administered nicotine to rats throughout gestation or in adulthood (postnatal days PN90-107), using regimens that reproduce plasma levels in smokers, assessing effects on serotonin (5HT) receptors, the 5HT transporter and responses mediated through adenylyl cyclase (AC). Evaluations were then made on PN105, PN110, PN120 and PN180. Prenatal nicotine exposure elicited persistent suppression of 5HT1A receptors and upregulation of 5HT2 receptors, effects that were selective for males and that first emerged in young adulthood. In addition, AC activity was reduced and there was uncoupling of receptor-mediated responses. With nicotine exposure restricted to adulthood, there were few changes in 5HT synaptic proteins during treatment or in the first 2 weeks post-treatment, distinctly different from the robust alterations seen earlier with similar nicotine regimens given in adolescence. Nevertheless, there was long-term upregulation of the proteins in males at 6 months of age; females were unaffected. Exposure to prenatal nicotine followed by adult nicotine overcame the protection of females, so that they, too showed long-term effects not seen with either treatment alone; the effects in males were exacerbated in an additive manner. Our results indicate that the effects of nicotine during prenatal or adolescent stages are indeed distinct from the effects in adults, but that even adults show persistent changes after nicotine exposure, commensurate with the sensitization-homeostasis model. These effects may contribute to lifelong vulnerability to readdiction.

Differential effects of psychoactive drugs in adolescents and adults

It is well known that most people who use psychoactive drugs started as teenagers. In spite of this, there has been little preclinical research on the effects of psychostimulants during adolescence. Recently, however, a number of laboratories have begun to focus on drug effects in adolescents as compared with adults. The data show that there are unique responses to drugs during this period of development. This review will focus on our current understanding of neurochemical and behavioral drug effects during adolescence.

Adolescent vs. adult-onset nicotine self-administration in male rats: duration of effect and differential nicotinic receptor correlates

Adolescence is the life stage when tobacco addiction typically begins. Adolescent neurobehavioral development may be altered by nicotine self-administration in a way that persistently potentiates addiction. Previously, we showed that female adolescent rats self-administer more nicotine than do adults and that the increased nicotine intake then persists through the transition to adulthood [E.D. Levin, A. Rezvani, D. Montoya, J. Rose, H. Swartzwelder, Adolescent-onset nicotine self-administration modeled in female rats, Psychopharmacology 169 (2003) 141-149.]. In the current study, male Sprague-Dawley rats were given access to nicotine via the standard operant IV self-administration procedure (nicotine bitartrate dose of 0.03 mg/kg/infusion). One group of male rats started during adolescence the other group started in young adulthood. After the end of the four-week period of self-administration brain regions of the rats were assessed for alpha4beta2 nicotinic receptor binding. We found that male rats, like females, show higher nicotine self-administration when starting during adolescence as compared to starting in adulthood (p<0.001). Indeed, the effect in adolescent males was even greater than that in females, with more than triple the rate of nicotine self-administration vs. the adult-onset group during the first 2 weeks. The adolescent onset nicotine-self-administering rats also had significantly greater high affinity nicotinic receptor binding in the midbrain and the striatum, whereas hippocampal binding did not differ between the age groups. Striatal values significantly correlated with nicotine self-administration during the first 2 weeks in the adult-onset group but not the adolescent-onset rats, suggesting that the differences in self-administration may depend in part on underlying disparities in synaptic responses to nicotine. After the initial 2 weeks, nicotine self-administration in male rats declined toward adult-like levels, as the adolescent rats approached adulthood. This study showed that adolescent male rats self-administer significantly more nicotine than do male adult rats, but that adolescent-onset nicotine self-administration in male rats declines over weeks of continued use to approach adult-onset levels. In a previous study, we found that female rats also show greater nicotine self-administration with adolescent onset vs. adult onset, but that the females continued higher rates of self-administration into adulthood. Our results thus reinforce the concept that the adolescent brain is unusually receptive to the effects of nicotine in a manner that reinforces the potential for addiction.

Increased nicotine self-administration following prenatal exposure in female rats

There is a significant association between maternal cigarette smoking during pregnancy and greater subsequent risk of smoking in female offspring. In animal models, prenatal nicotine exposure causes persistent alterations in cholinergic and monoaminergic systems, both of which are important for nicotine actions underlying tobacco addiction. Accordingly, the current study was conducted to determine if there is a cause-and-effect relationship between prenatal nicotine exposure and nicotine self-administration starting in adolescence. Pregnant rats were administered nicotine (6 mg/kg/day) by osmotic minipump infusion throughout gestation and then, beginning in adolescence and continuing into adulthood, female offspring were given access to nicotine via a standard operant IV self-administration procedure (0.03 mg/kg/infusion). Gestational nicotine exposure did not alter the initial rate of nicotine self-administration. However, when animals underwent one week of forced abstinence and then had a second opportunity to self-administer nicotine, the prenatally-exposed animals showed a significantly greater rate of self-administration than did the controls. Prenatal nicotine exposure causes increased nicotine self-administration, which is revealed only when the animals are allowed to experience a period of nicotine abstinence. This supports a cause-and-effect relationship between the higher rates of smoking in the daughters of women who smoke cigarettes during pregnancy and implicates a role for nicotine in this effect. Our results further characterize the long-term liabilities of maternal smoking but also point to the potential liabilities of nicotine-based treatments for smoking cessation during pregnancy.

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.

Prenatal nicotine exposure alters the responses to subsequent nicotine administration and withdrawal in adolescence: Serotonin receptors and cell signaling

Offspring of women who smoke during pregnancy are themselves more likely to take up smoking in adolescence, effects that are associated with a high rate of depression and increased sensitivity to withdrawal symptoms. To evaluate the biological basis for this relationship, we assessed effects on serotonin (5-hydroxytryptamine, 5HT) receptors and 5HT-mediated cellular responses in rats exposed to nicotine throughout prenatal development and then given nicotine in adolescence (postnatal days PN30-47.5), using regimens that reproduce plasma nicotine levels found in smokers. Evaluations were then made during the period of adolescent nicotine treatment and for up to one month after the end of treatment. Prenatal nicotine exposure, which elicits damage to 5HT projections in the cerebral cortex and striatum, produced sex-selective changes in the expression of 5HT(1A) and 5HT2 receptors, along with induction of adenylyl cyclase (AC), leading to sensitization of heterologous inputs operating through this signaling pathway. Superimposed on these effects, the AC response to 5HT was shifted toward inhibition. By itself, adolescent nicotine administration, which damages the same pathways, produced similar effects on receptors and the 5HT-mediated response, but a smaller overall induction of AC. Animals exposed to prenatal nicotine showed a reduced response to nicotine administered in adolescence, results in keeping with earlier findings of persistent desensitization. Our results indicate that prenatal nicotine exposure alters parameters of 5HT synaptic communication lasting into adolescence and changes the response to nicotine administration and withdrawal in adolescence, actions which may contribute to a subpopulation especially vulnerable to nicotine dependence.

Maternal smoking during late pregnancy and offspring smoking behaviour

We explored the influence of maternal smoking during late pregnancy on the likelihood of smoking among offspring in adolescence and adulthood, using birth cohort data collected in the United Kingdom as part of the 1958 National Child Development Study. Longitudinal analysis indicated that maternal smoking during late pregnancy was associated with an increased likelihood of being a non-smoker at 16-year, 23-year and 33-year follow-up. This association differed between male and female offspring, with women showing no significant association and men showing an increased likelihood of being a non-smoker. There did not appear to be any association between maternal smoking during late pregnancy and cigarette consumption among offspring who reported smoking for either sex. These results are inconsistent with some previous reports that maternal smoking during pregnancy increases the likelihood of smoking among female offspring, although the observation of a moderating effect of sex on smoking behaviour is consistent with several previous reports. We discuss possible mechanisms for this association, and suggest factors that may account for the observed sex differences in this association, and the discrepancy between our results and some previous reports.

Exposure to smoke during development: fetal programming of adult disease

It is well established that smoking has potent effects on a number of parameters including food intake, body weight, metabolism, and blood pressure. For example, it is well documented that 1) there is an inverse relationship between smoking and body weight, and 2) smoking cessation is associated with weight gain. However, there is increasing evidence that smoking can exert deleterious effects on energy balance through maternal exposure during fetal development. Specifically, there appears to be an increased incidence of metabolic disease (including obesity), and cardiovascular disease in children and adults that were exposed to smoke during fetal development. The present review will examine the relationship between maternal smoke and adult disease in offspring. The epidemiological studies highlighting this relationship will be reviewed as well as the experimental animal models that point to potential mechanisms underlying this relationship. A better understanding of how smoking effects changes in energy balance may lead to treatments to ameliorate the long-lasting effects of perinatal exposure to smoke as well as increasing the health benefits associated with smoking cessation.

Visuospatial memory deficits emerging during nicotine withdrawal in adolescents with prenatal exposure to active maternal smoking

Active maternal smoking during pregnancy elevates the risk of cognitive deficits and tobacco smoking among offspring. Preclinical work has shown that combined prenatal and adolescent exposure to nicotine produces more pronounced hippocampal changes and greater deficits in cholinergic activity upon nicotine withdrawal than does prenatal or adolescent exposure to nicotine alone. Few prior studies have examined the potential modifying effects of gestational exposure to active maternal smoking on cognitive or brain functional response to tobacco smoking or nicotine withdrawal in adolescents. We examined visuospatial and verbal memory in 35 adolescent tobacco smokers with prenatal exposure to active maternal smoking and 26 adolescent tobacco smokers with no prenatal exposure to maternal smoking who were similar in age, educational attainment, general intelligence, and baseline plasma cotinine. Subjects were studied during ad libitum smoking and after 24 h of abstinence from smoking. A subset of subjects from each group also underwent functional magnetic resonance imaging while performing a visuospatial encoding and recognition task. Adolescent tobacco smokers with prenatal exposure experienced greater nicotine withdrawal-related deficits in immediate and delayed visuospatial memory relative to adolescent smokers with no prenatal exposure. Among adolescent smokers with prenatal exposure, nicotine withdrawal was associated with increased activation of left parahippocampal gyrus during early recognition testing of visuospatial stimuli and increased activation of bilateral hippocampus during delayed recognition testing of visuospatial stimuli. These findings extend prior preclinical work and suggest that, in human adolescent tobacco smokers, prenatal exposure to active maternal smoking is associated with alterations in medial temporal lobe function and concomitant deficits in visuospatial memory.

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.

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.

Longitudinal analysis of the effect of prenatal nicotine exposure on subsequent smoking behavior of offspring

We explored the influence of maternal smoking during pregnancy on the likelihood of smoking among offspring in adolescence and adulthood using data from two similar British birth cohort surveys, the 1958 National Child Development Study and the 1970 British Birth Survey. Similar information was available in each cohort on maternal age at delivery, offspring sex, maternal smoking during pregnancy, parental and offspring socioeconomic status, and parental smoking at the time offspring smoking was assessed at age 16 years. Offspring smoking at 16 years and at 30/33 years were the primary outcomes of interest. Our data support an association between maternal smoking during pregnancy and an increased risk of offspring smoking later in life among female offspring but not among male offspring. Female offspring of mothers who smoked during pregnancy were more likely to smoke at 16 years than were their male counterparts. Moreover, in this same subgroup, female offspring smoking at 16 years was associated with an increased likelihood of smoking at 30/33 years. Further investigation in larger studies with greater detail of factors shaping smoking in childhood and adulthood and biochemically verified outcome measures would be desirable to clarify the relationship.

The possible contribution of neuronal nicotinic acetylcholine receptors in depression

Although tobacco use and smoking were introduced long ago, it was only recently that the nicotine contained in the tobacco leaves was recognized as an addictive substance acting on the central nervous system (CNS). However, even prior to this recognition, several studies have reported an association between smoking and psychiatric disorders. One of the many observations was that smoking cessation is accompanied by a marked increase in the probability of major depression. In parallel with the discovery of the neuronal nicotinic acetylcholine receptors and their extensive expression in the CNS, this association sheds new light on the influence of cholinergic transmission in depression. In this article, we examine the various modes of action of nicotine in the CNS and discuss the mechanisms by which this alkaloid can prevent or precipitate mood disorders, and the possibility of discovering new therapeutic avenues for the treatment of depression.

Alpha7 nicotinic acetylcholine receptors targeted by cholinergic developmental neurotoxicants: nicotine and chlorpyrifos

Alpha7 nicotinic acetylcholine receptors (nAChRs) play a role in axonogenesis, synaptogenesis and synaptic plasticity, and are therefore potential targets for developmental neurotoxicants. We administered nicotine to neonatal rats during discrete periods spanning the onset and peak of axonogenesis/synaptogenesis, focusing on three brain regions with disparate distributions of cell bodies and neural projections: brainstem, forebrain and cerebellum. Nicotine treatment on postnatal days (PN) 1-4 had little or no effect on alpha7 nAChRs but treatment during the second (PN11-14) or third (PN21-24) weeks elicited significant decrements in receptor expression in brainstem and cerebellum, regions containing cell bodies that project to the forebrain. Exposure to chlorpyrifos, a neurotoxicant pesticide that acts partially through cholinergic mechanisms, also elicited deficits in alpha7 nAChRs during the second postnatal week but not the first week. For both nicotine and chlorpyrifos, the effects on alpha7 nAChRs were distinct from those on the alpha4beta2 subtype. Continuous prenatal nicotine exposure, which elicits subsequent, postnatal deficits in axonogenesis and synaptogenesis, also produced delayed-onset changes in alpha7 nAChRs, characterized by reductions in the forebrain and upregulation in the brainstem and cerebellum, a pattern consistent with impaired axonogenesis/synaptogenesis and reactive sprouting. Males were more sensitive to the persistent effects of prenatal nicotine exposure on alpha7 nAChRs, a pattern that mimics neurobehavioral deficits resulting from this treatment. The present findings reinforce the mechanistic involvement of alpha7 nAChRs in the actions of developmental neurotoxicants, and its biomarker potential for neuroteratogens that target neuritic outgrowth.

Maternal smoking, drinking or cannabis use during pregnancy and neurobehavioral and cognitive functioning in human offspring

Teratological investigations have demonstrated that agents that are relatively harmless to the mother may have significant negative consequences to the fetus. Among these agents, prenatal alcohol, nicotine or cannabis exposure have been related to adverse offspring outcomes. Although there is a relatively extensive body of literature that has focused upon birth and behavioral outcomes in newborns and infants after prenatal exposure to maternal smoking, drinking and, to a lesser extent, cannabis use, information on neurobehavioral and cognitive teratogenic findings beyond these early ages is still quite limited. Furthermore, most studies have focused on prenatal exposure to heavy levels of smoking, drinking or cannabis use. Few recent studies have paid attention to low or moderate levels of exposure to these substances. This review endeavors to provide an overview of such studies, and includes animal findings and potential mechanisms that may explain the mostly subtle effects found on neurobehavioral and cognitive outcomes. It is concluded that prenatal exposure to either maternal smoking, alcohol or cannabis use is related to some common neurobehavioral and cognitive outcomes, including symptoms of ADHD (inattention, impulsivity), increased externalizing behavior, decreased general cognitive functioning, and deficits in learning and memory tasks.

Nicotine effects on the activity of mice exposed prenatally to the nicotinic agonist anatoxin-a

Anatoxin-a is a nicotinic agonist produced by several genera of cyanobacteria, and has caused numerous deaths of wildlife, livestock and domestic animals world-wide. Several studies in the literature have shown that exposure of mice and rats to nicotine early in development alters its effects when the rodents are subsequently challenged with nicotine. We therefore determined the effect of nicotine on the motor activity of adult mice that had been exposed prenatally to anatoxin-a. Pregnant CD-1 mice received either saline vehicle or one of two doses of (+/-) anatoxin-a (125, 200 microg/kg), i.p., on GD13-17. As adults (8 months), control mice of both genders were used to determine the effect of nicotine (0, 0.1, 0.3, 1.0 or 3.0 mg/kg, s.c.) on motor activity measured for 30-min in a photocell device. Under these conditions, nicotine produced dose-related decreases in both horizontal and vertical activity, with an ED50 estimated to be 0.65 mg/kg. Next, additional control mice and mice exposed prenatally to anatoxin-a received the nicotine ED50 and saline vehicle, in a counterbalanced fashion, with one week separating treatments. Nicotine decreased both horizontal and vertical activity in all mice, regardless of prenatal anatoxin-a treatment. Thus, no enduring effects of prenatal anatoxin-a were obtained in adult mice following nicotine challenge.

Is prenatal tobacco exposure a risk factor for early adolescent smoking? A follow-up study

Recent reports indicate a relation between prenatal tobacco exposure (PTE) and offspring smoking. Many of these reports have been retrospective or have not included important variables such as other prenatal substance exposures, maternal and child psycho-social characteristics, mother's current smoking, and friends' smoking. No prior study has examined the timing of PTE. In this prospective study of a birth cohort of 567 14-year-olds, we examined the relation between trimester-specific PTE, offspring smoking, and other correlates of adolescent smoking. Average age of the adolescents was 14.8 years (range: 13.9-16.6 years), 51% were female, 54% were African-American. Data on maternal tobacco and other substance use were collected both prenatally and postnatally, 51% of the mothers were prenatal smokers and 53% smoked when their children were 14 years. PTE in the third trimester significantly predicted offspring smoking (ever/never, smoking level, age of onset) when demographic and other prenatal substances were included in the analyses. PTE remained a significant predictor of the level of adolescent smoking when maternal and child psychological characteristics were added to the model. When more proximal measures of the child's smoking were included in the model, including mother's current smoking and friends' smoking, PTE was no longer significant. Significant predictors of adolescent smoking at age 14 were female gender, Caucasian race, child externalizing behavior, maternal anxiety, and child depressive symptoms. Although direct effects of PTE on offspring smoking behavior have previously been reported from this study and by others, by early-adolescence, this association is not significant after controlling for the more proximal covariates of adolescent smoking such as mother's current smoking and peer smoking.

Does prenatal nicotine exposure sensitize the brain to nicotine-induced neurotoxicity in adolescence?

Offspring of women who smoke during pregnancy are themselves more likely to take up smoking in adolescence. We evaluated neurotoxicant effects of prenatal and adolescent nicotine exposure in developing rats to evaluate whether these contribute to a biological basis for this relationship. Rats were given nicotine or vehicle throughout pregnancy and the offspring then again received nicotine or vehicle during adolescence (postnatal days PN30-47.5); this regimen reproduces the plasma nicotine levels found in smokers. Indices of neural cell number (DNA concentration and content), cell size (protein/DNA ratio), and cell membrane surface area (membrane/total protein) were then evaluated in brain regions during adolescent nicotine administration (PN45) and up to 1 month post-treatment. By itself, prenatal nicotine administration produced cellular alterations that persisted into adolescence, characterized by net cell losses in the midbrain and to a lesser extent, in the cerebral cortex, with corresponding elevations in the membrane/total protein ratio. The hippocampus showed a unique response, with increased DNA content and regional enlargement. Adolescent nicotine treatment alone had similar, albeit smaller effects, but also showed sex-dependence, with effects on protein biomarkers preferential to females. When animals exposed to nicotine prenatally were then given nicotine in adolescence, the net outcome was worsened, largely representing summation of the two individual effects. Our results indicate that prenatal nicotine exposure alters parameters of cell development lasting into adolescence, where the effects add to those elicited directly by adolescent nicotine; neurotoxicant actions may thus contribute to the association between maternal smoking and subsequent smoking in the offspring.