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

Examining Predictors of Nicotine Dependence in Korean Adolescents : Comparing Ever Quitters and Never Quitters

Despite growing research on adolescent smokers, evidence for the differences between the two smoker groups who are ever quitters and never quitters is limited. The study aimed to examine predictors of nicotine dependence (ND) in Korean adolescents by comparing ever quitters and never quitters. Data from 349 adolescents were collected through an online survey. Among respondents, most of them were male, living with families, and were enrolled at schools. Data were analyzed by dividing participants into two groups - ever quitters and never quitters. The study found that adolescents' ND was commonly predicted by smoking peers and anxiety. However, schooling status was significantly associated with ever quitters' ND only. In the total sample, never-quitters were associated with higher ND compared to ever-quitters. This study did not control for differences among ever quitters in terms of the number of attempts to quit smoking and did not significantly control age effects in the sample. Based on study results, we suggest various policy implications. Cessation intervention should be designed keeping in mind the smokers' previous quit attempts and their motivation. It is also recommended that individually tailored smoking cessation programs be used to address the heterogenous nature of the adolescents.

Cyanobacterial anatoxin-a does not induce in vitro developmental neurotoxicity, but changes gene expression patterns in co-exposure with all-trans retinoic acid

Cyanobacterial blooms are increasing in frequency and intensity globally, and impacting recreational waters as well as waters used for drinking water provisioning. They are sources of bioactive metabolites including retinoids and the neurotoxin anatoxin-a. Here, we investigated the effects of anatoxin-a on a differentiating in vitro human neural stem cell model previously characterised with retinoic acids. Effects on protein and gene expression upon exposure for 9 or 18 days to anatoxin-a alone or in co-exposure with all-trans retinoic acid were evaluated using a panel of neural and glial differentiation biomarkers. Anatoxin-a did not cause distinct developmental neurotoxicity alone, or in co-exposure with retinoic acid. However, in line with its excitotoxicity, in co-exposure with 200 nM all-trans retinoic acid it reduced the differentiation of acetylcholinergic neuron subtypes in the culture at 1000 nM (highest tested concentration). While this could have substantial functional implications for the developing nervous system, there is no indication for developmental neurotoxicity beyond its (excito-)toxicity to acetylcholinergic neurons, which only occurred in co-exposure to all-trans retinoic acid.

Choline-acetyltransferase (ChAT) and acetylcholinesterase (AChE) in the human infant dorsal motor nucleus of the Vagus (DMNV), and alterations according to sudden infant death syndrome (SIDS) category

Amongst other molecules, the cholinergic system consists of choline-acetyltransferase (ChAT, - synthesis enzyme), acetylcholinesterase (AChE - primary hydrolysis enzyme), and butyrylcholinesterase (BuChE - secondary hydrolysis enzyme). In the brainstem, the Dorsal Motor Nucleus of The Vagus (DMNV) has high cholinergic expression and is a region of interest in the neuropathology of sudden infant death syndrome (SIDS). SIDS is the unexpected death of a seemingly healthy infant, but postmortem brainstem abnormalities suggesting altered cholinergic regulation have been found. This study aimed to determine the percentage of positive ChAT and AChE neurons within the infant DMNV through immunohistochemistry at the three levels of the brainstem medulla (caudal, intermediate, and rostral), to investigate whether the proportion of neurons positive for these enzymes differs amongst the diagnostic subgroups of SIDS compared to those with an explained cause of Sudden unexpected death in infancy (eSUDI), and whether there were any associations with SIDS risk factors (male gender, cigarette smoke exposure, co-sleeping/bed sharing, and prone sleeping). Results showed that ChAT-positive neurons were lower in the rostral DMNV in the SIDS II cohort, and within the caudal and intermediate DMNV of infants who were exposed to cigarette smoke. These findings suggest altered cholinergic regulation in the brainstem of SIDS infants, with potential contribution of cigarette smoke exposure, presumably via the nicotinic acetylcholinergic receptor system.

Negative and positive allosteric modulators of the α7 nicotinic acetylcholine receptor regulates the ability of adolescent binge alcohol exposure to enhance adult alcohol consumption

Rationale and Objectives: Ethanol acts directly on the α7 Nicotinic acetylcholine receptor (α7). Adolescent-binge alcohol exposure (ABAE) produces deleterious consequences during adulthood, and data indicate that the α7 receptor regulates these damaging events. Administration of an α7 Negative Allosteric Modulator (NAM) or the cholinesterase inhibitor galantamine can prophylactically prevent adult consequences of ABAE. The goals of the experiments were to determine the effects of co-administration of ethanol and a α7 agonist in the mesolimbic dopamine system and to determine if administration of an α7 NAM or positive allosteric modulator (PAM) modulates the enhancement of adult alcohol drinking produced by ABAE. Methods: In adult rats, ethanol and the α7 agonist AR-R17779 (AR) were microinjected into the posterior ventral tegmental area (VTA), and dopamine levels were measured in the nucleus accumbens shell (AcbSh). In adolescence, rats were treated with the α7 NAM SB-277011-A (SB) or PNU-120596 (PAM) 2 h before administration of EtOH (ABAE). Ethanol consumption (acquisition, maintenance, and relapse) during adulthood was characterized. Results: Ethanol and AR co-administered into the posterior VTA stimulated dopamine release in the AcbSh in a synergistic manner. The increase in alcohol consumption during the acquisition and relapse drinking during adulthood following ABAE was prevented by administration of SB, or enhanced by administration of PNU, prior to EtOH exposure during adolescence. Discussion: Ethanol acts on the α7 receptor, and the α7 receptor regulates the critical effects of ethanol in the brain. The data replicate the findings that cholinergic agents (α7 NAMs) can act prophylactically to reduce the alterations in adult alcohol consumption following ABAE.

Nicotine on the developing brain

Developmental periods such as gestation and adolescence have enhanced plasticity leaving the brain vulnerable to harmful effects from nicotine use. Proper brain maturation and circuit organization is critical for normal physiological and behavioral outcomes. Although cigarette smoking has declined in popularity, noncombustible nicotine products are readily used. The misperceived safety of these alternatives lead to widespread use among vulnerable populations such as pregnant women and adolescents. Nicotine exposure during these sensitive developmental windows is detrimental to cardiorespiratory function, learning and memory, executive function, and reward related circuitry. In this review, we will discuss clinical and preclinical evidence of the adverse alterations in the brain and behavior following nicotine exposure. Time-dependent nicotine-induced changes in reward related brain regions and drug reward behaviors will be discussed and highlight unique sensitivities within a developmental period. We will also review long lasting effects of developmental exposure persisting into adulthood, along with permanent epigenetic changes in the genome which can be passed to future generations. Taken together, it is critical to evaluate the consequences of nicotine exposure during these vulnerable developmental windows due to its direct impact on cognition, potential trajectories for other substance use, and implicated mechanisms for the neurobiology of substance use disorders.

Gray matter volumes of the insula and anterior cingulate cortex and their dysfunctional roles in cigarette smoking

The salience network, including the insula and anterior cingulate cortex (ACC), has been implicated in nicotine addiction. Structural imaging studies have reported diminished insula and ACC gray matter volumes (GMVs) in smokers as compared to nonsmokers. However, it remains unclear how insula and ACC GMVs may relate to years of smoking, addiction severity, or behavioral traits known to dispose individuals to smoking. Here, with a dataset curated from the Human Connectome Project and voxel-based morphometry, we replicated the findings of smaller GMVs of the insula and medial prefrontal cortex, including the dorsal ACC and supplementary motor area (dACC/SMA), in (70 heavy < 209 light < 209 never) smokers matched in age, sex, and average daily num ber of drinks. The GMVs of the insula or dACC/SMA were not significantly correlated with years of smoking or Fagerstrom Test for Nicotine Dependence (FTND) scores. Heavy relative to never smokers demonstrated higher externalizing and internalizing scores, as evaluated by the NIH Emotion. In heavy smokers, the dACC/SMA but not insula GMV was positively correlated with both externalizing and internalizing scores. The findings together confirm volumetric changes in the salience network in heavy smokers and suggest potentially distinct dysfunctional roles of the insula and dACC/SMA in chronic smoking.

Long-term effects of early postnatal nicotine exposure on cholinergic function in the mouse hippocampal CA1 region

In rodent models of smoking during pregnancy, early postnatal nicotine exposure results in impaired hippocampus-dependent memory, but the underlying mechanism remains elusive. Given that hippocampal cholinergic systems modulate memory and rapid development of hippocampal cholinergic systems occurs during nicotine exposure, here we investigated its impacts on cholinergic function. Both nicotinic and muscarinic activation produce transient or long-lasting depression of excitatory synaptic transmission in the hippocampal CA1 region. We found that postnatal nicotine exposure impairs both the induction and nicotinic modulation of NMDAR-dependent long-term depression (LTD). Activation of muscarinic receptors decreases excitatory synaptic transmission and CA1 network activity in both wild-type and α2 knockout mice. These muscarinic effects are still observed in nicotine-exposed mice. M1 muscarinic receptor activity is required for mGluR-dependent LTD. Early postnatal nicotine exposure has no effect on mGluR-dependent LTD induction, suggesting that it has no effect on the function of m1 muscarinic receptors involved in this form of LTD. Our results demonstrate that early postnatal nicotine exposure has more pronounced effects on nicotinic function than muscarinic function in the hippocampal CA1 region. Thus, impaired hippocampus-dependent memory may arise from the developmental disruption of nicotinic cholinergic systems in the hippocampal CA1 region.

Investigating the effects of chronic perinatal alcohol and combined nicotine and alcohol exposure on dopaminergic and non-dopaminergic neurons in the VTA

The ventral tegmental area (VTA) is the origin of dopaminergic neurons and the dopamine (DA) reward pathway. This pathway has been widely studied in addiction and drug reinforcement studies and is believed to be the central processing component of the reward circuit. In this study, we used a well-established rat model to expose mother dams to alcohol, nicotine-alcohol, and saline perinatally. DA and non-DA neurons collected from the VTA of the rat pups were used to study expression profiles of miRNAs and mRNAs. miRNA pathway interactions, putative miRNA-mRNA target pairs, and downstream modulated biological pathways were analyzed. In the DA neurons, 4607 genes were differentially upregulated and 4682 were differentially downregulated following nicotine-alcohol exposure. However, in the non-DA neurons, only 543 genes were differentially upregulated and 506 were differentially downregulated. Cell proliferation, differentiation, and survival pathways were enriched after the treatments. Specifically, in the PI3K/AKT signaling pathway, there were 41 miRNAs and 136 mRNAs differentially expressed in the DA neurons while only 16 miRNAs and 20 mRNAs were differentially expressed in the non-DA neurons after the nicotine-alcohol exposure. These results depicted that chronic nicotine and alcohol exposures during pregnancy differentially affect both miRNA and gene expression profiles more in DA than the non-DA neurons in the VTA. Understanding how the expression signatures representing specific neuronal subpopulations become enriched in the VTA after addictive substance administration helps us to identify how neuronal functions may be altered in the brain.

Postnatal Smoke Exposure Further Increases the Hepatic Nicotine Metabolism in Prenatally Smoke Exposed Male Offspring and Is Linked with Aberrant Cyp2a5 Methylation

Prenatal smoke exposure (PreSE) is a risk factor for nicotine dependence, which is further enhanced by postnatal smoke exposure (PostSE). One susceptibility gene to nicotine dependence is Cytochrome P450 (CYP) 2A6, an enzyme responsible for the conversion of nicotine to cotinine in the liver. Higher CYP2A6 activity is associated with nicotine dependence and could be regulated through DNA methylation. In this study we investigated whether PostSE further impaired PreSE-induced effects on nicotine metabolism, along with Cyp2a5, orthologue of CYP2A6, mRNA expression and DNA methylation. Using a mouse model where prenatally smoke-exposed adult offspring were exposed to cigarette smoke for 3 months, enzyme activity, mRNA levels, and promoter methylation of hepatic Cyp2a5 were evaluated. We found that in male offspring, PostSE increased PreSE-induced cotinine levels and Cyp2a5 mRNA expression. In addition, both PostSE and PreSE changed Cyp2a5 DNA methylation in male groups. PreSE however decreased cotinine levels whereas it had no effect on Cyp2a5 mRNA expression or methylation. These adverse outcomes of PreSE and PostSE were most prominent in males. When considered in the context of the human health aspects, the combined effect of prenatal and adolescent smoke exposure could lead to an accelerated risk for nicotine dependence later in life.

Regulation of the deleterious effects of binge-like exposure to alcohol during adolescence by α7 nicotinic acetylcholine receptor agents: prevention by pretreatment with a α7 negative allosteric modulator and emulation by a α7 agonist in alcohol-preferring (P) male and female rats

RATIONALE AND OBJECTIVES

Binge-like alcohol consumption during adolescence associates with several deleterious consequences during adulthood including an increased risk for developing alcohol use disorder (AUD) and other addictions. Replicated preclinical data has indicated that adolescent exposure to binge-like levels of alcohol results in a reduction of choline acetyltransferase (ChAT) and an upregulation in the α7 nicotinic receptor (α7). From this information, we hypothesized that the α7 plays a critical role in mediating the effects of adolescent alcohol exposure.

METHODS

Male and female P rats were injected with the α7 agonist AR-R17779 (AR) once during 6 time points between post-natal days (PND) 29-37. Separate groups were injected with the α7 negative allosteric modulator (NAM) dehydronorketamine (DHNK) 2 h before administration of 4 g/kg EtOH (14 total exposures) during PND 28-48. On PND 75, all rats were given access to water and ethanol (15 and 30%) for 6 consecutive weeks (acquisition). All rats were then deprived of EtOH for 2 weeks and then, alcohol was returned (relapse).

RESULTS

Administration of AR during adolescence significantly increased acquisition of alcohol consumption during adulthood and prolonged relapse drinking in P rats. In contrast, administration of DHNK prior to binge-like EtOH exposure during adolescence prevented the increase in alcohol consumption observed during acquisition of alcohol consumption and the enhancement of relapse drinking observed during adulthood.

DISCUSSION

The data indicate that α7 mediates the effects of alcohol during adolescence. The data also indicate that α7 NAMs are potential prophylactic agents to reduce the deleterious effects of adolescent alcohol abuse.

Influence of Family Environment and Tobacco Addiction: A Short Report from a Post-Graduate Teaching Hospital, India

Background: The initiation of tobacco addiction is complex, and several factors contribute to the onset of this behavior. It is presumed that the influence of family environment may pose a key factor in tobacco addiction. Tobacco-use has been highly observed in the Jamnagar district of Saurashtra region of Gujarat, India. No earlier study has focused on determining the pervasiveness of tobacco-use in families of tobacco users and non-users in this geographical area. Thus, this study aimed to assess the practice and pattern of tobacco-use (smoking and/or tobacco-chewing) in the families of tobacco-user patients. Methods: We studied the families of 65 tobacco-user patients (Group 1) who visited an outpatient clinic of an Ayurvedic post-graduate hospital with complaints of cough were studied and compared with age and gender-matched non-tobacco users (Group 2). The prevalence of tobacco use among the parents, siblings, and children of both groups was analyzed and compared. Results: The findings revealed that tobacco use among parents, siblings, and children in Group 1 was higher than Group 2 (p < 0.001). This meant that the problems of tobacco addiction are not always related to the individual, and therefore, tobacco-prevention strategies should focus on the entire family. Conclusions: These findings offer further insight into the promotion of smoking prevention interventions. Nevertheless, further research is warranted.

Cigarette smoke exposure effects on the brainstem expression of nicotinic acetylcholine receptors (nAChRs), and on cardiac, respiratory and sleep physiologies

Cigarette smoking during pregnancy is the largest modifiable risk factor for adverse outcomes in the infant. Investigations have focused on the psychoactive component of cigarettes, nicotine. One proposed mechanism leading to adverse effects is the interaction between nicotine and its nicotinic acetylcholine receptors (nAChRs). Much data has been generated over the past three decades on the effects of cigarette smoke exposure (CSE) on the expression of the nAChRs in the brainstem and physiological parameters related to cardiac, respiration and sleep, in the offspring of smoking mothers and animal models of nicotine exposure. This review summarises this data and discusses the main findings, highlighting that findings in animal models closely correlate with those from human studies, and that the major brainstem sites where the expression level for the nAChRs are consistently affected include those that play vital roles in cardiorespiration (hypoglossal nucleus, dorsal motor nucleus of the vagus, nucleus of the solitary tract), chemosensation (nucleus of the solitary tract, arcuate nucleus) and arousal (rostral mesopontine sites such as the locus coeruleus and nucleus pontis oralis). These findings provide evidence for the adverse effects of CSE during and after pregnancy to the infant and the need to continue with the health campaign advising against CSE.

Calcium rises induced by AMPA and nicotine receptors in the ventral tegmental area show differences in mouse brain slices prenatally exposed to nicotine

Nicotine exposure during gestation is associated with a higher risk of adverse behavioral outcomes including a heightened liability for dependency to drugs of abuse, which can exhibit drug-specificity influenced by gender. This enhanced liability suggests that nicotine use during pregnancy alters neural development in circuits involved in motivation and reward-based learning. The ventral tegmental area (VTA) is critical in motivated behaviors and we hypothesized that gestational exposure to nicotine alters the development of excitatory circuits in this nucleus. Accordingly, in VTA brain slices from male and female mice exposed to nicotine during the prenatal period (PNE) and controls, we compared cellular rises in calcium induced by AMPA receptor and nicotinic acetylcholine receptor (nAChR) stimulation by use of the ratiometric calcium binding dye, Fura-2AM. We found that AMPA induced smaller amplitude calcium rises in the PNE VTA, which was an effect only detected in males. Further, while the amplitude did not vary between treatment and control in females, a greater number of cells responded with rises in calcium in the PNE. Conversely, the proportions of cells responding with calcium rises induced by nAChR stimulation did not change in either gender according to treatment. However, larger rises in calcium in PNE females were detected. When taken together our data show that excitatory signaling in the VTA is altered in a gender-specific manner by PNE and suggest that alterations in signaling could play a role in drug-specific differences in maladaptive, motivated behaviors exhibited by males and females born to mothers exposed to nicotine during pregnancy. © 2018 Wiley Periodicals, Inc. Develop Neurobiol 2018.

Differential Effects of Nicotine Exposure on the Hippocampus Across Lifespan

BACKGROUND

Nicotine exposure affects the hippocampus through activation of hippocampal nicotinic acetylcholine receptors (nAChRs), which are present throughout excitatory and inhibitory hippocampal circuitry. The role of cholinergic functioning in the hippocampus varies across developmental stages so that nicotine exposure differentially affects this region depending upon timing of exposure, producing developmentally distinct changes in structure, function, and behavior.

METHODS

We synthesize findings across literature in this area to comprehensively review current understanding of the unique effects of nicotine exposure on the hippocampus throughout the lifespan with a focus on hippocampal morphology, cholinergic functioning, and hippocampusdependent learning and memory.

CONCLUSIONS

Chronic and acute nicotine exposure differentially affect hippocampus structure, functioning, and related learning and memory in the perinatal period, adolescence, and aging. Age-related differences in sensitivity to nicotine exposure should be considered in the research of nicotine addiction and the development of nicotine addiction treatments.

Developmental toxicity of nicotine: A transdisciplinary synthesis and implications for emerging tobacco products

While the health risks associated with adult cigarette smoking have been well described, effects of nicotine exposure during periods of developmental vulnerability are often overlooked. Using MEDLINE and PubMed literature searches, books, reports and expert opinion, a transdisciplinary group of scientists reviewed human and animal research on the health effects of exposure to nicotine during pregnancy and adolescence. A synthesis of this research supports that nicotine contributes critically to adverse effects of gestational tobacco exposure, including reduced pulmonary function, auditory processing defects, impaired infant cardiorespiratory function, and may contribute to cognitive and behavioral deficits in later life. Nicotine exposure during adolescence is associated with deficits in working memory, attention, and auditory processing, as well as increased impulsivity and anxiety. Finally, recent animal studies suggest that nicotine has a priming effect that increases addiction liability for other drugs. The evidence that nicotine adversely affects fetal and adolescent development is sufficient to warrant public health measures to protect pregnant women, children, and adolescents from nicotine exposure.

Acute cocaine exposure elicits rises in calcium in arousal-related laterodorsal tegmental neurons

Cocaine has strong reinforcing properties, which underlie its high addiction potential. Reinforcement of use of addictive drugs is associated with rises in dopamine (DA) in mesoaccumbal circuitry. Excitatory afferent input to mesoaccumbal circuitry sources from the laterodorsal tegmental nucleus (LDT). Chronic, systemic cocaine exposure has been shown to have cellular effects on LDT cells, but acute actions of local application have never been demonstrated. Using calcium imaging, we show that acute application of cocaine to mouse brain slices induces calcium spiking in cells of the LDT. Spiking was attenuated by tetrodotoxin (TTX) and low calcium solutions, and abolished by prior exhaustion of intracellular calcium stores. Further, DA receptor antagonists reduced these transients, whereas DA induced rises with similar spiking kinetics. Amphetamine, which also results in elevated levels of synaptic DA, but via a different pharmacological action than cocaine, induced calcium spiking with similar profiles. Although large differences in spiking were not noted in an animal model associated with a heightened proclivity of acquiring addiction‐related behavior, the prenatal nicotine exposed mouse (PNE), subtle differences in cocaine's effect on calcium spiking were noted, indicative of a reduction in action of cocaine in the LDT associated with exposure to nicotine during gestation. When taken together, our data indicate that acute actions of cocaine do include effects on LDT cells. Considering the role of intracellular calcium in cellular excitability, and of the LDT in addiction circuitry, our data suggest that cocaine effects in this nucleus may contribute to the high addiction potential of this drug.

Maternal Smoking during Pregnancy and DNA-Methylation in Children at Age 5.5 Years: Epigenome-Wide-Analysis in the European Childhood Obesity Project (CHOP)-Study

Mounting evidence links prenatal exposure to maternal tobacco smoking with disruption of DNA methylation (DNAm) profile in the blood of infants. However, data on the postnatal stability of such DNAm signatures in childhood, as assessed by Epigenome Wide Association Studies (EWAS), are scarce. Objectives of this study were to investigate DNAm signatures associated with in utero tobacco smoke exposure beyond the 12th week of gestation in whole blood of children at age 5.5 years, to replicate previous findings in young European and American children and to assess their biological role by exploring databases and enrichment analysis. DNA methylation was measured in blood of 366 children of the multicentre European Childhood Obesity Project Study using the Illumina Infinium HM450 Beadchip (HM450K). An EWAS was conducted using linear regression of methylation values at each CpG site against in utero smoke exposure, adjusted for study characteristics, biological and technical effects. Methylation levels at five HM450K probes in MYO1G (cg12803068, cg22132788, cg19089201), CNTNAP2 (cg25949550), and FRMD4A (cg11813497) showed differential methylation that reached epigenome-wide significance according to the false-discovery-rate (FDR) criteria (q-value<0.05). Whereas cg25949550 showed decreased methylation (-2% DNAm ß-value), increased methylation was observed for the other probes (9%: cg12803068; 5%: cg22132788; 4%: cg19089201 and 4%: cg11813497) in exposed relative to non-exposed subjects. This study thus replicates previous findings in children ages 3 to 5, 7 and 17 and confirms the postnatal stability of MYO1G, CNTNAP2 and FRMD4A differential methylation. The role of this differential methylation in mediating childhood phenotypes, previously associated with maternal smoking, requires further investigation.

Adolescents and adults differ in the immediate and long-term impact of nicotine administration and withdrawal on cardiac norepinephrine

Cardiovascular responses to smoking cessation may differ in adolescents compared to adults. We administered nicotine by osmotic minipump infusion for 17 days to adolescent and adult rats (30 and 90 days of age, respectively) and examined cardiac norepinephrine levels during treatment, after withdrawal, and for months after cessation. In adults, nicotine evoked a significant elevation of cardiac norepinephrine and a distinct spike upon withdrawal, after which the levels returned to normal; the effect was specific to males. In contrast, adolescents did not show significant changes during nicotine treatment or in the immediate post-withdrawal period. However, beginning in young adulthood, males exposed to adolescent nicotine showed sustained elevations of cardiac norepinephrine, followed by later-emerging deficits that persisted through six months of age. We then conducted adolescent exposure using twice-daily injections, a regimen that augments stress associated with inter-dose withdrawal episodes. With the injection route, adolescents showed an enhanced cardiac norepinephrine response, reinforcing the relationship between withdrawal stress and a surge in cardiac norepinephrine levels. The relative resistance of adolescents to the acute nicotine withdrawal response is likely to make episodic nicotine exposure less stressful or aversive than in adults. Equally important, the long-term changes after adolescent nicotine exposure resemble those known to be associated with risk of hypertension in young adulthood (elevated norepinephrine) or subsequent congestive heart disease (norepinephrine deficits). Our findings reinforce the unique responses and consequences of nicotine exposure in adolescence, the period in which most smokers commence tobacco use.

The intergenerational transmission of tobacco habit: Role of parents and the family

Introduction:

Tobacco pandemic has become one of the greatest public health challenges of all time. The socio-environmental factors prevailing at home have been identified as one of the most important causes of adopting smoking and other types of smokeless tobacco.

Objectives:

The present study was conducted to find out the prevalence and pattern of tobacco use in the patients registered in the clinic and to study the role of parental and family influence on tobacco use.

Materials and Methodology:

This cross-sectional study was performed in a Tertiary Care Hospital in Delhi. The study included all 307 patients who were registered in a cardiac clinic between January and December 2014. The history of tobacco use in siblings, offspring, and parents was taken from these patients. Pedigree profiles provided detailed information about tobacco use in the family. The association between the use of tobacco among parents and tobacco habits was assessed by odds ratio and Chi-square test.

Results:

Among the patients, 48% were tobacco users and family history of tobacco use was present in 81% of users. Odds ratio of tobacco use in parents, offspring, siblings, and three generations was 3.477, 1.987, 2.626, and 7.626 than that of nontobacco users.

Conclusion:

Previous anti-smoking campaigns have concentrated much of their effort on discouraging individuals from smoking with the aim of creating a nonsmoking generation. This approach does not take sufficient account of the fact, reconfirmed by our findings that children are influenced by the behavior and attitudes of adults, especially their parents.

Nicotinic acetylcholine receptors: upregulation, age-related effects and associations with drug use

Nicotinic acetylcholine receptors are ligand-gated ion channels that exogenously bind nicotine. Nicotine produces rewarding effects by interacting with these receptors in the brain's reward system. Unlike other receptors, chronic stimulation by an agonist induces an upregulation of receptor number that is not due to increased gene expression in adults; while upregulation also occurs during development and adolescence there have been some opposing findings regarding a change in corresponding gene expression. These receptors have also been well studied with regard to human genetic associations and, based on evidence suggesting shared genetic liabilities between substance use disorders, numerous studies have pointed to a role for this system in comorbid drug use. This review will focus on upregulation of these receptors in adulthood, adolescence and development, as well as the findings from human genetic association studies which point to different roles for these receptors in risk for initiation and continuation of drug use.

Prenatal Maternal Substance Use and Offspring Outcomes

Evidence from both human and preclinical studies seems to indicate that maternal smoking, alcohol drinking, or other drug use during pregnancy can affect offspring outcomes. It also suggests that maternal substance use during pregnancy is a major preventable cause of adverse infant outcomes. Nonetheless, more recent studies applying genetically sensitive designs cast some doubt on the causality of the relationship between prenatal maternal substance use and infant and child behavioral outcomes. In this review, recent findings in this field of research are provided, with attention to correlated risk factors of maternal substance use during pregnancy and preclinical studies focusing on plausible biological pathways. Next, evidence-based interventions targeting maternal substance use during pregnancy are discussed. Finally, possible interventions targeting the correlated risk factors and recommendations for clinical work are presented.

Associations between the prenatal environment and cardiovascular risk factors in adolescent girls: Internalizing and externalizing behavior symptoms as mediators

This longitudinal study examines links among adolescent internalizing and externalizing symptoms, the prenatal environment (e.g., nicotine exposure) and pre/perinatal maternal health, and cardiovascular risk factors. Girls (N=262) ages 11-17 reported internalizing and externalizing behaviors and mothers reported about the prenatal environment and maternal health during and 3 months post-pregnancy. Adolescent cardiovascular risk included adiposity, smoking, blood pressure, and salivary C-reactive protein. Internalizing symptoms mediated relations between prenatal exposures/maternal health and adiposity; externalizing symptoms mediated relations between prenatal exposures and adolescent smoking. Healthcare providers who attend to internalizing and externalizing symptoms in girls may ultimately influence cardiovascular health, especially among those with pre/perinatal risk factors.

Impact of prenatal nicotine on the structure of midbrain dopamine regions in the rat

In utero exposure of rats to nicotine (NIC) provides a useful animal model for studying the impact of smoking during pregnancy on human offspring. Certain sequelae of prenatal NIC exposure suggest an impact on the development of the midbrain dopamine (DA) system, which receives a robust cholinergic innervation from the mesopontine tegmentum. We therefore investigated whether prenatal NIC induced structural changes in cells and synapses within the midbrain that persisted into adulthood. Osmotic minipumps delivering either sodium bitartrate (vehicle; VEH) or NIC bitartrate at 2 mg/kg/day were implanted into nine timed-pregnant dams at E4. At birth, rat pups were culled to litters of six males each, and the litters were cross-fostered. Plasma levels of NIC and cotinine from killed pups provided evidence of NIC exposure in utero. Pups separated from dams at weaning showed a trend toward reduced locomotor activity at this time point but not when tested again in adulthood. Adult rats were killed for anatomical studies. Estimates of brain size and volume did not vary with NIC treatment. Midbrain sections stained for Nissl or by immunoperoxidase for tyrosine hydroxylase and analyzed using unbiased stereology revealed no changes in volume or cell number in the substantia nigra compacta or ventral tegmental area as a result of NIC exposure. Within the ventral tegmental area, electron microscopic physical disector analysis showed no significant differences in the number of axon terminals or the number of asymmetric (putative excitatory) or symmetric (putative inhibitory) synapses. Although too infrequent to estimate by unbiased stereology, no obvious difference in the proportion of cholinergic axons was noted in NIC- versus VEH-treated animals. These data suggest that activation of nicotinic receptors during prenatal development induces no significant modifications in the structure of cells in the ventral midbrain when assessed in adulthood.

Prenatal nicotine alters the developmental neurotoxicity of postnatal chlorpyrifos directed toward cholinergic systems: better, worse, or just "different?"

This study examines whether prenatal nicotine exposure sensitizes the developing brain to subsequent developmental neurotoxicity evoked by chlorpyrifos, a commonly-used insecticide. We gave nicotine to pregnant rats throughout gestation at a dose (3mg/kg/day) producing plasma levels typical of smokers; offspring were then given chlorpyrifos on postnatal days 1-4, at a dose (1mg/kg) that produces minimally-detectable inhibition of brain cholinesterase activity. We evaluated indices for acetylcholine (ACh) synaptic function throughout adolescence, young adulthood and later adulthood, in brain regions possessing the majority of ACh projections and cell bodies; we measured nicotinic ACh receptor binding, hemicholinium-3 binding to the presynaptic choline transporter and choline acetyltransferase activity, all known targets for the adverse developmental effects of nicotine and chlorpyrifos given individually. By itself nicotine elicited overall upregulation of the ACh markers, albeit with selective differences by sex, region and age. Likewise, chlorpyrifos alone had highly sex-selective effects. Importantly, all the effects showed temporal progression between adolescence and adulthood, pointing to ongoing synaptic changes rather than just persistence after an initial injury. Prenatal nicotine administration altered the responses to chlorpyrifos in a consistent pattern for all three markers, lowering values relative to those of the individual treatments or to those expected from simple additive effects of nicotine and chlorpyrifos. The combination produced global interference with emergence of the ACh phenotype, an effect not seen with nicotine or chlorpyrifos alone. Given that human exposures to nicotine and chlorpyrifos are widespread, our results point to the creation of a subpopulation with heightened vulnerability.

Nicotine during pregnancy: changes induced in neurotransmission, which could heighten proclivity to addict and induce maladaptive control of attention

Prenatal exposure to nicotine, occurring either via maternal smoking or via use of transdermal nicotine patches to facilitate cigarette abstinence by pregnant women, is associated with ∼ 13% of pregnancies worldwide. Nicotine exposure during gestation has been correlated with several negative physiological and psychosocial outcomes, including heightened risk for aberrant behaviors involving alterations in processing of attention as well as an enhanced liability for development of drug dependency. Nicotine is a terotogen, altering neuronal development of various neurotransmitter systems, and it is likely these alterations participate in postnatal deficits in attention control and facilitate development of drug addiction. This review discusses the alterations in neuronal development within the brain's major neurotransmitter systems, with special emphasis placed on alterations within the laterodorsal tegmental nucleus, in light of the role this cholinergic nucleus plays in attention and addiction. Changes induced within this nucleus by gestational exposure to nicotine, in combination with changes induced in other brain regions, are likely to contribute to the transgenerational burden imposed by nicotine. Although neuroplastic changes induced by nicotine are not likely to act in isolation, and are expected to interact with epigenetic changes induced by preconception exposure to drugs of abuse, unraveling these changes within the developing brain will facilitate eventual development of targeted treatments for the unique vulnerability for arousal disorders and development of addiction within the population of individuals who have been prenatally exposed to nicotine.

Electrophysiological changes in laterodorsal tegmental neurons associated with prenatal nicotine exposure: implications for heightened susceptibility to addict to drugs of abuse

Prenatal nicotine exposure (PNE) is a risk factor for developing an addiction to nicotine at a later stage in life. Understanding the neurobiological changes in reward related circuitry induced by exposure to nicotine prenatally is vital if we are to combat the heightened addiction liability in these vulnerable individuals. The laterodorsal tegmental nucleus (LDT), which is comprised of cholinergic, GABAergic and glutamatergic neurons, is importantly involved in reward mediation via demonstrated excitatory projections to dopamine-containing ventral tegmental neurons. PNE could lead to alterations in LDT neurons that would be expected to alter responses to later-life nicotine exposure. To examine this issue, we monitored nicotine-induced responses of LDT neurons in brain slices of PNE and drug naive mice using calcium imaging and whole-cell patch clamping. Nicotine was found to induce rises in calcium in a smaller proportion of LDT cells in PNE mice aged 7-15 days and smaller rises in calcium in PNE animals from postnatal ages 11-21 days when compared with age-matched control animals. While inward currents induced by nicotine were not found to be different, nicotine did induce larger amplitude excitatory postsynaptic currents in PNE animals in the oldest age group when compared with amplitudes induced in similar-aged control animals. Immunohistochemically identified cholinergic LDT cells from PNE animals exhibited slower spike rise and decay slopes, which likely contributed to the wider action potential observed. Further, PNE was associated with a more negative action potential afterhyperpolarization in cholinergic cells. Interestingly, the changes found in these parameters in animals exposed prenatally to nicotine were age related, in that they were not apparent in animals from the oldest age group examined. Taken together, our data suggest that PNE induces changes in cholinergic LDT cells that would be expected to alter cellular excitability. As the changes are age related, these PNE-associated alterations could contribute differentially across ontogeny to nicotine-mediated reward and may contribute to the particular susceptibility of in utero nicotine exposed individuals to addict to nicotine upon nicotine exposure in the juvenile period.

Maternal smoking during pregnancy and offspring smoking initiation: assessing the role of intrauterine exposure

AIMS

To assess whether associations between maternal smoking during pregnancy and offspring smoking initiation are due to intrauterine mechanisms.

DESIGN

Comparison of associations of maternal and partner smoking behaviour during pregnancy with offspring smoking initiation using partner smoking as a negative control (n = 6484) and a Mendelian randomization analysis (n = 1020), using a genetic variant in the mothers as a proxy for smoking cessation during pregnancy.

SETTING

A longitudinal birth cohort in South West England.

PARTICIPANTS

Participants of the Avon Longitudinal Study of Parents and Children (ALSPAC).

MEASUREMENTS

Smoking status during pregnancy was self-reported by mother and partner in questionnaires administered at pregnancy. Latent classes of offspring smoking initiation (non-smokers, experimenters, late-onset regular smokers and early-onset regular smokers) were previously developed from questionnaires administered at 14-16 years. A genetic variant, rs1051730, was genotyped in the mothers.

FINDINGS

Both mother and partner smoking were similarly positively associated with offspring smoking initiation classes, even after adjustment for confounders. Odds ratios (OR) [95% confidence interval (CI)] for class membership compared with non-smokers were: experimenters: mother OR = 1.33 (95% CI = 1.06, 1.67), partner OR = 1.28 (95% CI = 1.06, 1.55), late-onset regular smokers: mother OR = 1.80 (95% CI = 1.43, 2.26), partner OR = 1.86 (95% CI = 1.52, 2.28) and early-onset regular smokers: mother OR = 2.89 (95% CI = 2.12, 3.94), partner OR = 2.50 (95% CI = 1.85, 3.37). There was no clear evidence for a dose-response effect of either mother or partner smoking heaviness on class membership. Maternal rs1051730 genotype was not clearly associated with offspring smoking initiation class in pre-pregnancy smokers (P = 0.35).

CONCLUSION

The association between smoking during pregnancy and offspring smoking initiation does not appear to operate through intrauterine mechanisms.

Environmental enrichment alters structural plasticity of the adolescent brain but does not remediate the effects of prenatal nicotine exposure

Exposure to both drugs of abuse and environmental enrichment (EE) are widely studied experiences that induce large changes in dendritic morphology and synaptic connectivity. As there is an abundance of literature using EE as a treatment strategy for drug addiction, we sought to determine whether EE could remediate the effects of prenatal nicotine (PN) exposure. Using Golgi-Cox staining, we examined eighteen neuroanatomical parameters in four brain regions [medial prefrontal cortex (mPFC), orbital frontal cortex (OFC), nucleus accumben, and Par1] of Long-Evans rats. EE in adolescence dramatically altered structural plasticity in the male and female brain, modifying 60% of parameters investigated. EE normalized three parameters (OFC spine density and dendritic branching and mPFC dendritic branching) in male offspring exposed to nicotine prenatally but did not remediate any measures in female offspring. PN exposure interfered with adolescent EE-induced changes in five neuroanatomical measurements (Par1 spine density and dendritic branching in both male and female offspring, and mPFC spine density in male offspring). And in four neuroanatomical parameters examined, PN exposure and EE combined to produce additive effects [OFC spine density in females and mPFC dendritic length (apical and basilar) and branching in males]. Despite demonstrated efficacy in reversing drug addiction, EE was not able to reverse many of the PN-induced changes in neuronal morphology, indicating that modifications in neural circuitry generated in the prenatal period may be more resistant to change than those generated in the adult brain.

Prenatal tobacco smoke exposure, risk of schizophrenia, and severity of positive/negative symptoms

Prenatal exposure to cigarette smoke causes chronic fetal hypoxia, dysregulation of endocrine equilibrium, and disruption of fetal neurodevelopment associated with brain malfunction, all of which potentially could induce vulnerability to schizophrenia. A total of 212 schizophrenia patients aged 14-30years, and 212 matched controls were studied. Prenatal tobacco smoke exposure of the schizophrenia patients was compared to that of the normal controls by applying logistic regression analysis and controlling for several confounding factors. The outcomes of interest were comparison of the frequency of maternal and paternal smoking between patients and controls, as well as the severity of positive and negative symptoms between the offspring of smoking and nonsmoking parents. Among the mothers of schizophrenia patients and controls, 92 (43.4%) and 46 (21.7%) smoked, respectively. Maternal smoking during pregnancy had a significant unique contribution on increasing the risk for development of schizophrenia (p=0.001), and a greater severity of negative symptoms (p=0.023). Paternal smoking did not have a significant effect on the risk of schizophrenia, or severity of negative symptoms. The findings suggest that maternal smoking during pregnancy puts offspring at an increased risk for later schizophrenia, with increased severity of negative symptoms. Given the wide practice of smoking during pregnancy, fetal exposure to tobacco smoke could be a major preventable neurodevelopmental factor that increases vulnerability to schizophrenia.

Exploring alternate processes contributing to the association between maternal smoking and the smoking behavior among young adult offspring

INTRODUCTION

Maternal smoking during pregnancy (MSP) is a known risk factor for regular smoking in young adulthood and may pose a risk independently of mother's lifetime smoking. The processes through which MSP exerts this influence are unknown but may occur through greater smoking quantity and frequency following initiation early in adolescence or increased sensitivity to nicotine dependence (ND) at low levels of smoking.

METHODS

This study used path analysis to investigate adolescent smoking quantity, smoking frequency, and ND as potential simultaneous mediating pathways through which MSP and mother's lifetime smoking (whether she has ever smoked) increase the risk of smoking in young adulthood among experimenters (at baseline, <100 cigarettes/lifetime) and current smokers (>100 cigarettes/lifetime).

RESULTS

For experimenters, MSP was directly associated with more frequent young adult smoking and was not mediated by adolescent smoking behavior or ND. Independently of MSP, the effect of mother's lifetime smoking was fully mediated through frequent smoking and was heightened ND during adolescence. Controlling for MSP eliminated a previously observed direct association between mother's lifetime smoking and future smoking among experimenters. For current smokers, only prior smoking behavior was associated with future smoking frequency.

CONCLUSIONS

These results seem to rule out sensitivity to ND and increased smoking behavior as contributing pathways of MSP. Further, the impact of MSP on young adult smoking extends beyond that of having an ever-smoking mother. Future work should test other possible mediators; for example, MSP-related epigenetic changes or gene variants influencing the brain's nicotine response.

Methamidophos exposure during the early postnatal period of mice: immediate and late-emergent effects on the cholinergic and serotonergic systems and behavior

Organophosphates (OPs) are among the most used pesticides. Although some OPs have had their use progressively more restricted, other OPs are being used without sufficient investigation of their effects. Here, we investigated the immediate neurochemical and delayed neurochemical and behavioral actions of the OP methamidophos to verify whether there are concerns regarding exposure during early postnatal development. From the third to the nineth postnatal day (PN), Swiss mice were sc injected with methamidophos (1mg/kg). At PN10, we assessed cholinergic and serotonergic biomarkers in the cerebral cortex and brainstem. From PN60 to PN63, mice were submitted to a battery of behavioral tests and subsequently to biochemical analyses. At PN10, the effects were restricted to females and to the cholinergic system: Methamidophos promoted increased choline transporter binding in the brainstem. At PN63, in the brainstem, there was a decrease in choline transporter, a female-only decrease in 5HT1A and a male-only increase in 5HT2 receptor binding. In the cortex, choline acetyltransferase activity was decreased and 5HT2 receptor binding was increased both in males and females. Methamidophos elicited behavioral alterations, suggestive of increased depressive-like behavior and impaired decision making. There were no significant alterations on anxiety-related measures and on memory/learning. Methamidophos elicited cholinergic and serotonergic alterations that depended on brain region, sex, and age of the animals. These outcomes, together with the behavioral effects, indicate that this OP is deleterious to the developing brain and that alterations are indeed identified long after the end of exposure.

Prenatal dexamethasone augments the sex-selective developmental neurotoxicity of chlorpyrifos: implications for vulnerability after pharmacotherapy for preterm labor

Glucocorticoids are routinely given in preterm labor and are also elevated by maternal stress; organophosphate exposures are virtually ubiquitous, so coexposures to these two agents are pervasive. We administered dexamethasone to pregnant rats on gestational days 17-19 at a standard therapeutic dose (0.2mg/kg); offspring were then given chlorpyrifos on postnatal days 1-4, at a dose (1mg/kg) that produces barely-detectable (<10%) inhibition of brain cholinesterase activity. We evaluated indices for acetylcholine (ACh) synaptic function throughout adolescence, young adulthood and later adulthood, in brain regions possessing the majority of ACh projections and cell bodies; we measured nicotinic ACh receptor binding, hemicholinium-3 binding to the presynaptic choline transporter and choline acetyltransferase activity, all known targets for the adverse developmental effects of dexamethasone and chlorpyrifos given individually. Dexamethasone did not enhance the systemic toxicity of chlorpyrifos, as evidenced by weight gain and measurements of cholinesterase inhibition during chlorpyrifos treatment. Nevertheless, it enhanced the loss of presynaptic ACh function selectively in females, who ordinarily show sparing of organophosphate developmental neurotoxicity relative to males. Females receiving the combined treatment showed decrements in choline transporter binding and choline acetyltransferase activity that were unique (not found with either treatment alone), as well as additive decrements in nicotinic receptor binding. On the other hand, males given dexamethasone showed no augmentation of the effects of chlorpyrifos. Our findings indicate that prior dexamethasone exposure could create a subpopulation that is especially vulnerable to the adverse effects of organophosphates or other developmental neurotoxicants.

Prenatal nicotine exposure alters neuroanatomical organization of the developing brain

Although there has been considerable research conducted regarding the long-term effects of prenatal exposure to nicotine, there has been little examination of how this experience influences brain development. This study was designed to examine if there are morphological changes (dendritic branching, dendritic length, and spine density) in medial prefrontal cortex, orbital frontal cortex, parietal cortex, and nucleus accumbens associated with exposure to nicotine during gestation. Nicotine or saline was administered to pregnant Long Evans dams for the duration of pregnancy. Golgi-Cox techniques were used to examine neuroanatomy of offspring at postnatal day 21. The dendritic changes identified in rats exposed to nicotine prenatally resembled neuroanatomical changes that are identified in rats administered with nicotine in adulthood. Of the 18 anatomical parameters measured, 11 exhibited significant modification, with two parameters apical and basilar spine density in parietal cortex demonstrating sex-dependent modification. These early changes in anatomy and behavior have important implications for later plasticity and long-term well-being.

Risk factors for adolescent smoking: parental smoking and the mediating role of nicotine dependence

BACKGROUND

Parental smoking and early-emerging nicotine dependence symptoms are well-documented risk factors for adolescent smoking. However, very little is known about the mediating pathways through which these risk factors may act, or whether parental smoking may cause or signal early-emerging nicotine dependence symptoms.

METHODS

Data were drawn from the longitudinal Social and Emotional Contexts of Adolescent Smoking Patterns Study. Adolescents who had smoked under 100 cigarettes in their lifetime (n=594; low-exposure group) and adolescents who had smoked over 100 cigarettes, but fewer than 5 cigarettes per day (n=152) were included in the analyses. Path analysis was performed on longitudinal data to investigate the association between parental smoking and smoking frequency at the 48 months follow-up, both directly and through mediating variables of smoking frequency, smoking quantity, and nicotine dependence.

RESULTS

Father's smoking was associated with higher adolescent nicotine dependence scores at the baseline assessment wave. Structural equation modeling revealed that mother's smoking at baseline was associated with adolescent's smoking frequency at the 48-month follow-up, and its effect was partially mediated by both smoking frequency and nicotine dependence among low-exposure adolescent smokers.

CONCLUSIONS

Parental smoking is a risk factor for future smoking in low-exposure adolescent smokers, above and beyond the risks posed by smoking behavior and nicotine dependence. Moreover, parental smoking is associated with early-onset nicotine dependence in low-exposure adolescent smokers. As an easily measureable risk factor, parent smoking status can be used to identify and intervene with novice adolescent smokers who are at high risk for chronic smoking behavior.

Prenatal nicotine exposure alters postnatal cardiorespiratory integration in young male but not female rats

The present study tested the hypothesis that prenatal nicotine exposure (PNE) induces sex specific alternations in indices of cardiorespiratory coupling during early development. Rat pups exposed to either nicotine (6 mg/kg/day) or saline (control) in utero were chronically instrumented with ECG electrodes for measurement of heart rate (HR) and respiratory frequency (RF) was monitored by whole body plethysmography on postnatal days (P)13, P16 and P26. PNE had no identifiable effect on resting respiratory frequency (RF) in either sex. There was however a strong trend (p=0.057) for resting HR to be elevated by PNE in male offspring only. Alternatively, the HR response to hypoxia (10% O(2)), was significantly blunted at P13 but significantly elevated at P26 s in the absence of any significant change in RF in PNE males only. Indicators of respiratory sinus arrhythmia (RSA) were also significantly reduced in P26 PNE males. No significant effects of PNE on HR, RF or RSA were identified in female offspring at any age. Our results demonstrate that PNE induces very specific changes in cardiorespiratory integration at select postnatal ages and these changes are more prominent in males. Additionally, alternations in cardiorespiratory integration appear to persist into later development in males only, potentially increasing the risk for cardiovascular diseases such as hypertension later in life.

Quantitative Molecular Imaging of Neuronal Nicotinic Acetylcholine Receptors in the Human Brain with A-85380 Radiotracers

Neuronal nicotinic acetylcholine receptors (nAChRs) have been implicated in a spectrum of cognitive functions as well as psychiatric and neurodegenerative disorders, including tobacco addiction and Alzheimer's Disease. The examination of neuronal nAChRs in living humans is a relatively new field. Researchers have developed brain-imaging radiotracers for nAChRs, with radiolabeled A-85380 compounds having the most widespread use. We provide a brief background on nAChRs, followed by a discussion of the development and application of A-85380 radiotracers in human imaging studies. We describe potential future studies using nicotinic receptor radioligands for the study of tobacco addiction, including the mechanism of action of the smoking-cessation therapy varenicline. Throughout this review, we focus on the significant potential that resides in the identification and quantification of nAChRs in the living human brain.

The long-term effects of prenatal nicotine exposure on neurologic development

A large body of documented evidence has found that smoking during pregnancy is harmful to both the mother and the fetus. Prenatal exposure to nicotine in various forms alters neurologic development in experimental animals and may increase the risk for neurologic conditions in humans. There is a positive association between maternal smoking and sudden infant death syndrome (SIDS); however, the connection between nicotine addiction, depression, attention disorders, and learning and behavior problems in humans is not straightforward. Nicotine's action on the production and function of neurotransmitters makes it a prime suspect in the pathology of these diseases. Nicotine accentuates neurotransmitter function in adults but desensitizes these functions in prenatally exposed infants and children. This desensitization causes an abnormal response throughout the lifespan. Furthermore, nicotine use by adolescents and adults can alleviate some of the symptoms caused by these neurotransmitter problems while they increase the risk for nicotine addiction. Although nicotine replacement drugs are used by pregnant women, there is no clear indication that they improve outcomes during pregnancy, and they may add to the damage that occurs to the developing neurologic system in the fetus. Understanding the effects of nicotine exposure is important in providing safe care for pregnant women, children, and families and for developing appropriate smoking cessation programs during pregnancy.

Mimicking maternal smoking and pharmacotherapy of preterm labor: interactions of fetal nicotine and dexamethasone on serotonin and dopamine synaptic function in adolescence and adulthood

Fetal coexposure to nicotine and dexamethasone is common: maternal smoking increases the incidence of preterm delivery and glucocorticoids are the consensus treatment for prematurity. We gave pregnant rats 3mg/kg/day of nicotine throughout gestation, a regimen that reproduces smokers' plasma levels, and then on gestational days 17, 18 and 19, we administered 0.2mg/kg of dexamethasone. We evaluated developmental indices for serotonin (5HT) and dopamine synaptic function throughout adolescence, young adulthood and later adulthood, assessing the brain regions possessing major 5HT and dopamine projections and cell bodies. Males displayed persistent upregulation of 5HT(1A) and 5HT(2) receptors and the 5HT transporter, with a distinct hierarchy of effects: nicotine<dexamethasone<combined treatment. Females showed downregulation of the 5HT(1A) receptor with the same rank order; both sexes displayed presynaptic hyperactivity of 5HT and dopamine pathways as evidenced by increased neurotransmitter turnover. Superimposed on these overall effects, there were significant differences in temporal and regional relationships among the different treatments, often involving effects that emerged later in life, after a period of apparent normality. This indicates that nicotine and dexamethasone do not simply produce an initial neuronal injury that persists throughout the lifespan but rather, they alter the developmental trajectory of synaptic function. The fact that the combined treatment produced greater effects for many parameters points to potentially worse neurobehavioral outcomes after pharmacotherapy of preterm labor in the offspring of smokers.

Additive and synergistic effects of fetal nicotine and dexamethasone exposure on cholinergic synaptic function in adolescence and adulthood: Implications for the adverse consequences of maternal smoking and pharmacotherapy of preterm delivery

Maternal smoking contributes to preterm delivery; glucocorticoids are the consensus treatment for prematurity, thus producing fetal coexposure to nicotine and dexamethasone. We administered nicotine to pregnant rats throughout gestation at a dose (3 mg/kg/day) producing plasma levels typical of smokers. Later in gestation, animals received dexamethasone (0.2 mg/kg). We assessed developmental indices for acetylcholine (ACh) synaptic function throughout adolescence, young adulthood and later adulthood, evaluating brain regions possessing major ACh projections and cell bodies; we measured choline acetyltransferase activity, hemicholinium-3 binding to the presynaptic choline transporter and nicotinic ACh receptor binding. In general, nicotine and dexamethasone, alone or in combination, produced regionally-selective increases or decreases in choline acetyltransferase activity but larger, consistent elevations in hemicholinium-3 and nicotinic ACh receptor binding; the patterns were indicative of ACh synaptic hyperactivity. Superimposed on these overall effects, there were significant disparities in temporal and regional relationships among the different treatments, notably involving effects that emerged later in life, after a period of apparent normality. This indicates that nicotine and dexamethasone do not simply produce an initial ACh neuronal injury that then persists throughout the lifespan but rather, they alter the developmental trajectory of ACh function. Most importantly, the combined exposure to nicotine + dexamethasone elicited greater changes than either of the individual exposures, involving both additive and synergistic effects. Our results thus point to potentially worse neurobehavioral outcomes of the pharmacotherapy of preterm labor in the offspring of smokers.

From the American Academy of Pediatrics: Technical report--Secondhand and prenatal tobacco smoke exposure

Secondhand tobacco smoke (SHS) exposure of children and their families causes significant morbidity and mortality. In their personal and professional roles, pediatricians have many opportunities to advocate for elimination of SHS exposure of children, to counsel tobacco users to quit, and to counsel children never to start. This report discusses the harms of tobacco use and SHS exposure, the extent and costs of tobacco use and SHS exposure, and the evidence that supports counseling and other clinical interventions in the cycle of tobacco use. Recommendations for future research, policy, and clinical practice change are discussed. To improve understanding and provide support for these activities, the harms of SHS exposure are discussed, effective ways to eliminate or reduce SHS exposure are presented, and policies that support a smoke-free environment are outlined.

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.

Increased apoptosis and reduced neuronal and glial densities in the hippocampus due to nicotine and ethanol exposure in adolescent mice

It has been recently shown that nicotine and ethanol interact during adolescence affecting memory/learning and anxiety levels. Considering the role of the hippocampus in both anxiety and memory/learning, we investigated whether adolescent nicotine and/or ethanol administration elicit apoptotic cell death and whether this results in neuronal and/or glial density alterations in the following regions of the hippocampus: granular layer of the dentate gyrus (GrDG), molecular layer (Mol), CA1, CA2 and CA3. From the 30th to the 45th postnatal day, C57BL/6 male and female mice were exposed to nicotine free base (NIC) and/or ethanol (ETOH). Four groups were analyzed: (1) concomitant NIC (50mug/ml in 2% saccharin to drink) and ETOH (25%, 2g/kg i.p. injected every other day) exposure; (2) NIC exposure; (3) ETOH exposure; (4) vehicle. We evaluated cell degeneration (TUNEL assay), neuronal and glial densities (optical disector) and region thicknesses at the end of the period of exposure. Our results demonstrate that ETOH elicited an increase in TUNEL-positive cells relative to the vehicle group in all hippocampal regions. NIC elicited less severe region-dependent effects: the number of TUNEL-positive cells was significantly increased in the Mol and CA1 when compared to the vehicle group. These results were paralleled by reductions in neuronal and glial cells densities, which indicate that both cell types are sensitive to the neurotoxic effects of these drugs. There were no effects on region thicknesses. On the other hand, concomitant NIC and ETOH reduced the adverse effects of the drugs when administered separately. This ability of nicotine and ethanol co-exposure to lessen the adverse effects of nicotine and ethanol may contribute to adolescents co-use and co-abuse of tobacco and alcoholic beverages.

Moderate use of alcohol, tobacco and cannabis during pregnancy: new approaches and update on research findings

Interest in fetal origins of adverse offspring outcomes has grown extensively in the last decade. This has resulted in many published studies focusing on exposure in utero to substances and human offspring outcomes. Exposure to maternal substance use in pregnancy is believed to be a preventable hazard, and is therefore a main issue for public health concern and policy. However, an important question in human studies remains whether prenatal substance use exposure has an aetiological role in pathways to adverse developmental and behavioural outcomes via teratological effects. Recent insights and developments in research methodology will aid the adequate and more refined testing of associations between prenatal substance use and offspring outcomes. In particular, novel approaches could assist in disentangling the exposure to substance effects from correlated risk factors. The purpose of this manuscript is therefore to provide an overview of methodological issues involved in studies that focus on the association between maternal substance use during pregnancy and offspring's outcomes, to describe novel approaches to test these associations, and present some examples of new and well-designed studies and discuss their findings.