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

Early developmental risks for tobacco addiction: A probabilistic epigenesis framework

Considerable progress has been made in elucidating the relationships between early life psychobiological and environmental risk factors and the development of tobacco addiction. However, a comprehensive understanding of the heterogeneity in tobacco addiction phenotypes requires integrating research findings. The probabilistic epigenesis meta-theory offers a valuable framework for this integration, considering systemic, multilevel, developmental, and evolutionary perspectives. In this paper, we critically review relevant research on early developmental risks associated with tobacco addiction and highlight the integrative heuristic value of the probabilistic epigenesis framework for this research. For this, we propose a four-level systems approach as an initial step towards integration, analyzing complex interactions among different levels of influence. Additionally, we explore a coaction approach to examine key interactions between early risk factors. Moreover, we introduce developmental pathways to understand interindividual differences in tobacco addiction risk during development. This integrative approach holds promise for advancing our understanding of tobacco addiction etiology and informing potentially effective intervention strategies.

Prenatal tobacco exposure on brain morphometry partially mediated poor cognitive performance in preadolescent children

Objectives

To evaluate whether prenatal tobacco exposure (PTE) is related to poorer cognitive performance, abnormal brain morphometry, and whether poor cognitive performance is mediated by PTE-related structural brain differences.

Methods

The Adolescent Brain Cognitive Development study dataset was used to compare structural MRI data and neurocognitive (NIH Toolbox®) scores in 9-to-10-year-old children with (n=620) and without PTE (n=10,989). We also evaluated whether PTE effects on brain morphometry mediated PTE effects on neurocognitive scores. Group effects were evaluated using Linear Mixed Models, covaried for socio-demographics and prenatal exposures to alcohol and/or marijuana, and corrected for multiple comparisons using the false-discovery rate (FDR).

Results

Compared to unexposed children, those with PTE had poorer performance (all p-values <0.05) on executive function, working memory, episodic memory, reading decoding, crystallized intelligence, fluid intelligence and overall cognition. Exposed children also had thinner parahippocampal gyri, smaller surface areas in the posterior-cingulate and pericalcarine cortices; the lingual and inferior parietal gyri, and smaller thalamic volumes (all p-values <0.001). Furthermore, among children with PTE, girls had smaller surface areas in the superior-frontal (interaction-FDR-p=0.01), precuneus (interaction-FDR-p=0.03) and postcentral gyri (interaction-FDR-p=0.02), while boys had smaller putamen volumes (interaction-FDR-p=0.02). Smaller surface areas across regions of the frontal and parietal lobes, and lower thalamic volumes, partially mediated the associations between PTE and poorer neurocognitive scores (p-values <0.001).

Conclusions

Our findings suggest PTE may lead to poorer cognitive performance and abnormal brain morphometry, with sex-specific effects in some brain regions, in pre-adolescent children. The poor cognition in children with PTE may result from the smaller areas and subcortical brain volumes.

The roles of familial transmission and smoking during pregnancy on executive function skills: A sibling-comparison study

This research examines maternal smoking during pregnancy and risk for poorer executive function in siblings discordant for exposure. Data (N = 173 families) were drawn from the Missouri Mothers and Their Children study, a sample, identified using birth records (years 1998-2005), in which mothers changed smoking behavior between two pregnancies (Child 1 [older sibling]: M age = 12.99; Child 2 [younger sibling]: M age = 10.19). A sibling comparison approach was used, providing a robust test for the association between maternal smoking during pregnancy and different aspects of executive function in early-mid adolescence. Results suggested within-family (i.e., potentially causal) associations between maternal smoking during pregnancy and one working memory task (visual working memory) and one response inhibition task (color-word interference), with increased exposure associated with decreased performance. Maternal smoking during pregnancy was not associated with stop-signal reaction time, cognitive flexibility/set-shifting, or auditory working memory. Initial within-family associations between maternal smoking during pregnancy and visual working memory as well as color-word interference were fully attenuated in a model including child and familial covariates. These findings indicate that exposure to maternal smoking during pregnancy may be associated with poorer performance on some, but not all skills assessed; however, familial transmission of risk for low executive function appears more important.

An intergenerational lifespan perspective on the neuroscience of prenatal substance exposure

Prenatal substance exposure has the potential to impact a variety of domains, with neurobiological effects that last throughout the lifespan. Different substances may impact the brain in both specific and diffuse ways; however, the aberrant neural outcomes following exposure tend to coalesce in three areas: (1) sensorimotor development; (2) arousal, motivation, and reward; and (3) executive functioning, impulse control, and emotion regulation. This manuscript represents a summary and update of a previous review (Morie et al., 2019). We organize this piece by domain and summarize data from published neuroimaging studies that examine the neural correlates of prenatal exposure across developmental stages. While the published neuroimaging literature in the area of prenatal exposure has a range of sampling concerns that may limit generalizability as well as longitudinal prediction, the findings to date do point to domains of interest warranting further study. With this caveat, we synthesize the extant findings to describe ways in which prenatal substance exposure is associated with developmental psychopathology and implicated in potentially aberrant behavioral patterns beginning in infancy and persisting through childhood, adolescence, adulthood, and even parenthood. We also examine how substance abuse may impact parenting behaviors that in turn influences infant and child behavior in ways that may be additive or obscure the direct teratological effects of prenatal exposure. Given this observation, we offer an additional intergenerational lens through which prenatal substance exposure should be studied.

Verbal and nonverbal memory in school-aged children born to opioid-dependent mothers

BACKGROUND

The potential long-term developmental effects of prenatal methadone and buprenorphine exposure during pregnancy are still largely unknown.

AIMS

We investigated memory function in school-aged children of women enrolled in opioid maintenance therapy (OMT) during pregnancy.

STUDY DESIGN

Prospective longitudinal cohort study.

SUBJECTS

Participants included 41 children (aged 9-11 years), 20 of which had histories of prenatal methadone or buprenorphine exposure.

OUTCOME MEASURES

Verbal and non-verbal memory function was assessed using four subtests from the Test of Memory and Learning - Second edition (TOMAL-2).

RESULTS

The OMT group scored lower on both the two non-verbal as well as the two verbal memory tasks, all p-values <.05. Group differences remained for three out of the four subtests after controlling for general IQ. Including maternal tobacco use during pregnancy increased the explanatory power of the model, R² change of 0.07, p = .04.

CONCLUSIONS

Children prenatally exposed to methadone or buprenorphine had significantly lower memory performance, however, this association may in part be explained by maternal tobacco use during pregnancy. Consequently, smoking cessation programs should be systematically integrated into opioid maintenance therapy programs for pregnant women.

Cognitive function in women with major mental illnesses who use tobacco

Cognitive effects of tobacco use among women with schizophrenia, bipolar disorder or depression have not been studied extensively as most studies focussed on men smokers. As part of a study on prevalence and cognitive effects of tobacco use, women with schizophrenia, bipolar disorder and depression were assessed for cognitive functioning using an information questionnaire derived from the Indian Post Graduate Institute Battery of Brain Dysfunction (PGIBBD) and the Trail Making Tests (TMT) A and B. The community dwelling women were clinically diagnosed and recruited from the outpatient department of a free tertiary care teaching hospital in India. The sample consisted of 321 women, 141 with schizophrenia (SZ), 80 with Bipolar Disorder (BD) and 100 with Recurrent Depressive Disorder (RDD). Tobacco users answered statistically significantly fewer questions on the PGIBBD Information Questionnaire. Users also took significantly more time to complete both TMT-A and TMT-B. Age, years of schooling and tobacco use were all significant co-variates for performance on cognitive tests. Tobacco users had lower motor speed and lesser visual scanning, poorer flexibility of thinking and working memory. Women with schizophrenia performed the worst. Tobacco use may exacerbate the cognitive dysfunction associated with major mental illnesses among women.

Prenatal drug exposure from infancy through emerging adulthood: Results from neuroimaging

Prenatal drug exposure may have important repercussions across the lifespan for cognition and behavior. While alcohol is a recognized teratogen, the influences of other substances may also be substantial. The neural underpinnings of the influences of prenatal drug exposure have been examined using longitudinal approaches and multiple imaging techniques. Here we review the existing literature on the neural correlates of prenatal drug exposure. We focused the review on studies that have employed functional neuroimaging and electroencephalography and on substances other than alcohol. We also framed the review through the lens of four developmental life stages (infancy, childhood, adolescence and emerging adulthood). We included papers that have examined any drug use, including tobacco, opiates, cocaine, marijuana, methamphetamines, or polysubstance use. Data suggest that prenatal drug exposure has long-lasting, deleterious influences on cognition and reward processing in infancy and childhood that persist into adolescence and emerging adulthood and may underlie some behavioral tendencies, such as increased externalizing and risk-taking behaviors, seen in these groups.

Phase IIb Trial of an α7 Nicotinic Receptor Partial Agonist With and Without Nicotine Patch for Withdrawal-Associated Cognitive Deficits and Tobacco Abstinence

PURPOSE/BACKGROUND

The objective of this study was to determine whether a novel α7 nicotinic acetylcholine receptor partial agonist improves cognition during nicotine withdrawal and improves abstinence rates. To do so, the effect of the α7 nicotinic acetylcholine receptor partial agonist, encenicline, on cognition and abstinence was evaluated when given as monotherapy and when combined with transdermal nicotine patch (nicotine replacement therapy [NRT]).

METHODS

Adult daily smokers, n = 160, who were motivated to quit smoking completed cognitive testing at satiated baseline and after overnight abstinence and then were randomized to receive a 12-week trial of encenicline 1 mg twice daily or identical placebo the day of the overnight abstinent cognitive testing. In the first 6 weeks of the 12-week encenicline administration, participants were also randomized to 6 weeks of NRT patch or placebo patch. Primary outcomes were cognition during abstinence and 7-day point-prevalence abstinence at week 12.

RESULTS

No beneficial effects of encenicline were observed on cognition or abstinence when compared with placebo or when combined with NRT compared with placebo capsule + NRT. Of the 4 conditions, abstinence rates were lowest among those assigned to encenicline alone.

CONCLUSIONS

Beneficial effects of NRT were observed on cognitive and abstinence outcomes when combined with encenicline compared with encenicline plus placebo patch. Addition of NRT to encenicline improved odds of abstinence approximately 3-fold compared with encenicline plus placebo patch. We conclude that encenicline, 1 mg/d, did not improve abstinence-associated cognitive impairment or abstinence rates as monotherapy or adjunctive therapy to NRT patch.

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.

Maternal Cigarette Smoke Exposure Worsens Neurological Outcomes in Adolescent Offspring with Hypoxic-Ischemic Injury

Hypoxic-ischemic (HI) encephalopathy occurs in approximately 6 per 1000 term newborns leading to devastating neurological consequences, such as cerebral palsy and seizures. Maternal smoking is one of the prominent risk factors contributing to HI injury. Mitochondrial integrity plays a critical role in neural injury and repair during HI. We previously showed that maternal cigarette smoke exposure (SE) can reduce brain mitochondrial fission and autophagosome markers in male offspring. This was accompanied by increased brain cell apoptosis (active caspase-3) and DNA fragmentation (TUNEL staining). Here, we aimed to investigate whether maternal SE leads to more severe neurological damage after HI brain injury in male offspring. Female BALB/c mice (8 weeks) were exposed to cigarette smoke prior to mating, during gestation, and lactation. At postnatal day 10, half of the pups from each litter underwent left carotid artery occlusion, followed by exposure to 8% oxygen (92% nitrogen). At postnatal day 40-44, maternal SE reduced grip strength in grip traction and foot fault tests, which were also reduced by HI injury to similar levels regardless of the maternal group. Limb coordination was impaired by maternal SE which was not worsened by HI injury. Maternal SE increased anxiety level in the offspring, which was normalized by HI injury. Apoptosis markers were increased in different brain regions by maternal SE, with the cortex having further increased TUNEL by HI injury, along with increased markers of inflammation and mitophagy. We conclude that maternal SE can worsen HI-induced cellular damage in male offspring well into adolescence.

Increased risk of developing schizophrenia in animals exposed to cigarette smoke during the gestational period

Cigarette smoking during the prenatal period has been investigated as a causative factor of obstetric abnormalities, which lead to cognitive and behavioural changes associated with schizophrenia. The aim of this study was to investigate behaviour and AChE activity in brain structures in adult rats exposed to cigarette smoke during the prenatal period. Pregnant rats were divided into non-PCSE (non-prenatal cigarette smoke exposure) and PCSE (prenatal cigarette smoke exposure) groups. On post-natal day 60, the rats received saline or ketamine for 7days and were subjected to behavioural tasks. In the locomotor activity task, the non-PCSE+ketamine and PCSE+ketamine groups exhibited increased locomotor activity compared with the saline group. In the social interaction task, the non-PCSE+ketamine and PCSE+ketamine groups exhibited an increased latency compared with the control groups. However, the PCSE+ketamine group exhibited a decreased latency compared with the non-PCSE+ketamine group, which indicates that the cigarette exposure appeared to decrease, the social deficits generated by ketamine. In the inhibitory avoidance task, the non-PCSE+ketamine, PCSE, and PCSE+ketamine groups exhibited impairments in working memory, short-term memory, and long-term memory. In the pre-pulse inhibition (PPI) test, cigarette smoke associated with ketamine resulted in impaired PPI in 3 pre-pulse (PP) intensity groups compared with the control groups. In the biochemical analysis, the AChE activity in brain structures increased in the ketamine groups; however, the PCSE+ketamine group exhibited an exacerbated effect in all brain structures. The present study indicates that exposure to cigarette smoke during the prenatal period may affect behaviour and cerebral cholinergic structures during adulthood.

The effects of nicotine on human fetal development

Maternal smoking during pregnancy continues to represent a major public health concern. Nicotine is extremely harmful to the developing fetus through many different mechanisms, and the harms increase with later gestational age at exposure. Pregnancies complicated by maternal nicotine use are more likely to have significant adverse outcomes. Nicotine-exposed children tend to have several health problems throughout their lives, including impaired function of the endocrine, reproductive, respiratory, cardiovascular, and neurologic systems. Poor academic performance and significant behavioral disruptions are also common, including ADHD, aggressive behaviors, and future substance abuse. To diminish the adverse effects from cigarette smoking, some women are turning to electronic cigarettes, a new trend that is increasing in popularity worldwide. They are largely perceived as being safer to use in pregnancy than traditional cigarettes, although there is not adequate evidence to support this claim. At this time, electronic cigarette use during pregnancy cannot be recommended. Birth Defects Research (Part C) 108:181-192, 2016. © 2016 Wiley Periodicals, Inc.

Gliotransmitter Release from Astrocytes: Functional, Developmental, and Pathological Implications in the Brain

Astrocytes comprise a large population of cells in the brain and are important partners to neighboring neurons, vascular cells, and other glial cells. Astrocytes not only form a scaffold for other cells, but also extend foot processes around the capillaries to maintain the blood–brain barrier. Thus, environmental chemicals that exist in the blood stream could have potentially harmful effects on the physiological function of astrocytes. Although astrocytes are not electrically excitable, they have been shown to function as active participants in the development of neural circuits and synaptic activity. Astrocytes respond to neurotransmitters and contribute to synaptic information processing by releasing chemical transmitters called “gliotransmitters.” State-of-the-art optical imaging techniques enable us to clarify how neurotransmitters elicit the release of various gliotransmitters, including glutamate, D-serine, and ATP. Moreover, recent studies have demonstrated that the disruption of gliotransmission results in neuronal dysfunction and abnormal behaviors in animal models. In this review, we focus on the latest technical approaches to clarify the molecular mechanisms of gliotransmitter exocytosis, and discuss the possibility that exposure to environmental chemicals could alter gliotransmission and cause neurodevelopmental disorders.

Nicotinic receptors, memory, and hippocampus

Nicotinic acetylcholine receptors (nAChRs) modulate the neurobiological processes underlying hippocampal learning and memory. In addition, nicotine's ability to desensitize and upregulate certain nAChRs may alter hippocampus-dependent memory processes. Numerous studies have examined the effects of nicotine on hippocampus-dependent learning, as well as the roles of low- and high-affinity nAChRs in mediating nicotine's effects on hippocampus-dependent learning and memory. These studies suggested that while acute nicotine generally acts as a cognitive enhancer for hippocampus-dependent learning, withdrawal from chronic nicotine results in deficits in hippocampus-dependent memory. Furthermore, these studies demonstrated that low- and high-affinity nAChRs functionally differ in their involvement in nicotine's effects on hippocampus-dependent learning. In the present chapter, we reviewed studies using systemic or local injections of acute or chronic nicotine, nAChR subunit agonists or antagonists; genetically modified mice; and molecular biological techniques to characterize the effects of nicotine on hippocampus-dependent learning.

Developmental consequences of fetal exposure to drugs: what we know and what we still must learn

Most drugs of abuse easily cross the placenta and can affect fetal brain development. In utero exposures to drugs thus can have long-lasting implications for brain structure and function. These effects on the developing nervous system, before homeostatic regulatory mechanisms are properly calibrated, often differ from their effects on mature systems. In this review, we describe current knowledge on how alcohol, nicotine, cocaine, amphetamine, Ecstasy, and opiates (among other drugs) produce alterations in neurodevelopmental trajectory. We focus both on animal models and available clinical and imaging data from cross-sectional and longitudinal human studies. Early studies of fetal exposures focused on classic teratological methods that are insufficient for revealing more subtle effects that are nevertheless very behaviorally relevant. Modern mechanistic approaches have informed us greatly as to how to potentially ameliorate the induced deficits in brain formation and function, but conclude that better delineation of sensitive periods, dose-response relationships, and long-term longitudinal studies assessing future risk of offspring to exhibit learning disabilities, mental health disorders, and limited neural adaptations are crucial to limit the societal impact of these exposures.

Prenatal nicotine exposure enhances Cx43 and Panx1 unopposed channel activity in brain cells of adult offspring mice fed a high-fat/cholesterol diet

Nicotine, the most important neuroteratogen of tobacco smoke, can reproduce brain and cognitive disturbances per se when administered prenatally. However, it is still unknown if paracrine signaling among brain cells participates in prenatal nicotine-induced brain impairment of adult offspring. Paracrine signaling is partly mediated by unopposed channels formed by connexins hemichannels (HCs) and pannexins serving as aqueous pores permeable to ions and small signaling molecules, allowing exchange between the intra- and extracellular milieus. Our aim was to address whether prenatal nicotine exposure changes the activity of those channels in adult mice offspring under control conditions or subjected to a second challenge during young ages: high-fat/cholesterol (HFC) diet. To induce prenatal exposure to nicotine, osmotic minipumps were implanted in CF1 pregnant mice at gestational day 5 to deliver nicotine bitartrate or saline (control) solutions. After weaning, offspring of nicotine-treated or untreated pregnant mice were fed ad libitum with chow or HFC diets for 8 weeks. The functional state of connexin 43 (Cx43) and pannexin 1 (Panx1) unopposed channels was evaluated by dye uptake experiments in hippocampal slices from 11-week-old mice. We found that prenatal nicotine increased the opening of Cx43 HCs in astrocytes, and Panx1 channels in microglia and neurons only if offspring mice were fed with HFC diet. Blockade of inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX₂) and prostaglandin E receptor 1 (EP₁), ionotropic ATP receptor type 7 (P2X₇) and NMDA receptors, showed differential inhibition of prenatal nicotine-induced channel opening in glial cells and neurons. Importantly, inhibition of the above mentioned enzymes and receptors, or blockade of Cx43 and Panx1 unopposed channels greatly reduced adenosine triphosphate (ATP) and glutamate release from hippocampal slices of prenatally nicotine-exposed offspring. We propose that unregulated gliotransmitter release through Cx43 and Panx1 unopposed channels may participate in brain alterations observed in offspring of mothers exposed to tobacco smoke during pregnancy.

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.

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.

Chronic exposure to cigarette smoke during gestation results in altered cholinesterase enzyme activity and behavioral deficits in adult rat offspring: potential relevance to schizophrenia

Prenatal cigarette smoke exposure (PCSE) has been associated with physiological and developmental changes that may be related to an increased risk for childhood and adult neuropsychiatric diseases. The present study investigated locomotor activity and cholinesterase enzyme activity in rats, following PCSE and/or ketamine treatment in adulthood. Pregnant female Wistar rats were exposed to 12 commercially filtered cigarettes per day for a period of 28 days. We evaluated motor activity and cholinesterase activity in the brain and serum of adult male offspring that were administered acute subanesthetic doses of ketamine (5, 15 and 25 mg/kg), which serves as an animal model of schizophrenia. To determine locomotor activity, we used the open field test. Cholinesterase activity was assessed by hydrolysis monitored spectrophotometrically. Our results show that both PCSE and ketamine treatment in the adult offspring induced increase of locomotor activity. Additionally, it was observed increase of acetylcholinesterase and butyrylcholinesterase activity in the brain and serum, respectively. We demonstrated that animals exposed to cigarettes in the prenatal period had increased the risk for psychotic symptoms in adulthood. This also occurs in a dose-dependent manner. These changes provoke molecular events that are not completely understood and may result in abnormal behavioral responses found in neuropsychiatric disorders, such as schizophrenia.

Effects of abstinence in adolescent tobacco smokers: withdrawal symptoms, urge, affect, and cue reactivity

INTRODUCTION

The aim of this study was to evaluate abstinence effects in adolescent daily smokers by examining the effects of experimentally manipulated acute smoking abstinence on measures including: (a) withdrawal symptoms, (b) reactive irritability, (c) smoking urges, (d) affect, and (e) responses to smoking cues.

METHODS

Participants (ages 13-19, 74 daily smokers, and 22 nonsmokers) completed baseline questionnaires and laboratory assessments (Session 1) and returned 1-4 days later to repeat the laboratory assessments (Session 2); half of the smokers were randomly assigned to overnight tobacco abstinence preceding Session 2.

RESULTS

During Session 2, abstinent smokers reported significantly greater increases in withdrawal symptoms, smoking urges, and negative affect compared with smokers who did not abstain and compared with nonsmokers. Although there was not a significant effect of abstinence on differential reactivity to smoking versus neutral cues, abstinence did result in significantly increased peak provoked urges and negative effect. There was not a significant effect of abstinence on positive affect or reactive irritability,

CONCLUSIONS

Our results suggest that adolescents experience increases in withdrawal symptoms, smoking urges (un-cued and peak provoked), and negative affect (un-cued and peak provoked) after acute smoking abstinence, but do not experience the increases in reactive irritability or decreases in positive affect that have been shown in adult smokers. Overall findings support the withdrawal relief and negative reinforcement models of smoking maintenance in adolescents and point to withdrawal, urge, and negative affect as important targets for treatment.

Prenatal-onset neurodevelopmental disorders secondary to toxins, nutritional deficiencies, and maternal illness

Neurodevelopmental disorders result from an inordinate number of genetic and environmental causes during the embryological and fetal periods of life. In the clinical setting, deciphering precise etiological diagnoses is often difficult. Newer screening technologies allow a gradual shift from traditional nature-versus-nurture debates toward the focused analysis of gene-by-environment interactions (G X E). Further understanding of developmental adaptation and plasticity requires consideration of epigenetic processes such as maternal nutritional status, environmental toxins, maternal illnesses, as well as genetic determinants, alone or in combination. Appreciation of specific G X E mechanisms of neurodevelopmental pathogenesis should lead to better risk-modifying or preventive strategies. We provide a brief overview of clinical and experimental observations that link prenatal-onset toxic exposures, metabolic disturbances, and maternal illnesses to certain neurodevelopmental disorders.

Intravenous gestational nicotine exposure results in increased motivation for sucrose reward in adult rat offspring

BACKGROUND

Prenatal tobacco smoke exposure is associated with alterations in motivated behavior in offspring, such as increased consumption of highly palatable foods and abused drugs. Animal models show that gestational nicotine (GN) exposure mediates changes in responding for sucrose and drug reward.

METHODS

A novel, intermittent low-dose intravenous (IV) exposure model was used to administer nicotine (0.05 mg/kg/injection) or saline 3×/day to rats on gestational days 8-21. Two experiments investigated the effect of IV GN on (1) the habituation of spontaneous locomotor activity and on (2) sucrose reinforced responding in offspring. For the operant experiments, animals acquired fixed-ratio (FR-3) responding for sucrose, 26% (w/v), and were tested on varying concentrations (0, 3, 10, 30, and 56%; Latin-square) according to a FR-3, and then a progressive-ratio (PR) schedule. Male and female adult offspring were used.

RESULTS

IV GN did not alter birth or growth weight, or the number of pups born. No between-group differences in habituation to spontaneous locomotor activity were observed. FR testing produced an inverted U-shaped response curve, and rats showed peak responding for 10% sucrose reinforcement. Neither gestation nor sex affected responding, suggesting equivalent sensitivity to varying sucrose concentrations. PR testing revealed that GN rats showed greater motivation for sucrose reinforcement relative to controls.

CONCLUSIONS

A low-dose, IV GN exposure model resulted in increased motivation to respond for sucrose reinforcement in adult offspring. This suggests that using a low number of cigarettes throughout pregnancy will result in increased motivation for highly palatable foods in adult, and perhaps, adolescent offspring.

The detrimental danger of Water-Pipe (Hookah) transcends the hazardous consequences of general health to the driving behavior

OBJECTIVE

To determine whether the consumption of tobacco used in Water-Pipe by drivers increases the risk of a motor vehicle collision as a consequence of hypoxia.

DESIGN

Analytical case-control study.

DATA SOURCES

Seventy exclusive Water-Pipe smokers (Experimental Group--EG)--mean age ± SD: 29.47 ± 10.45 years; mean number of weekly WPS, (6.9 ± 3.7); mean duration of WPS (WPS) is (7.5 ± 2.1 years)--and thirty non-smoker (Control Group--CG; mean age ± SD: 36.33 ± 13.92 years) were recruited during 2011 from two Arab villages located in the Galilee, northern Israel.

METHODS

We performed a case-control study exclusively among Water-Pipe smokers with an appropriate non smokers control group. Demographic questionnaire, Pulse Oxymeter for blood oxygenation measure and a driver simulator for measuring various participants driving behaviors were utilized. Statistical analysis for analyzing the different variables, Pearson's x2 analysis for the comparison of categorical variables, continuous variable is compared using Student's t-test and for testing the correlation between the different variables and bivariate correlation analysis were applied.

RESULTS

In the (EG) following WPS, we observed increase in the pulse rate--from 80 to 95 (t = 11.84, p < 0.05) and decrease in saturation level from 97.9 to 97.32, the decrease is statistically significant (t = 3.01, p < 0.05) versus no change in (CG). An increased number of accidents among EG (OR is 1.333 with CI of 1.008-1.776), while in CG, an insignificantly decrease (t = 3.08, p < 0.05). In EG an increase in centerline crossings (OR is 1.306 with CI of 1.016-1.679), also the total time not being within the lane was increased and the estimated (OR: 1.329; CI: 1.025-1.722). WPS increases the number of accidents by 33% and Hypoxia can cause driving behavioral turbulences.

CONCLUSION

The results show that WPS has a significant impact on driving behavior and on the risk of being involved in road accidents and causing driving to become riskier and less careful and stable. To the best of our knowledge, this is the first time such relationships have been tested. After WPS the total number of traffic accidents and driving violations increase. The results show a significant increase in the pulse rate immediately after WPS with a decrease in the saturation rate (the level of blood oxygenation); these changes continue half an hour after WPS.

Developmental nicotine exposure induced alterations in behavior and glutamate receptor function in hippocampus

In the developing brain, nicotinic acetylcholine receptors (nAChRs) are involved in cell survival, targeting, formation of neural and sensory circuits, and development and maturation of other neurotransmitter systems. This regulatory role is disrupted when the developing brain is exposed to nicotine, which occurs with tobacco use during pregnancy. Prenatal nicotine exposure has been shown to be a strong risk factor for memory deficits and other behavioral aberrations in the offspring. The molecular mechanisms underlying these neurobehavioral outcomes are not clearly elucidated. We used a rodent model to assess behavioral, neurophysiological, and neurochemical consequences of prenatal nicotine exposure in rat offspring with specific emphasis on the hippocampal glutamatergic system. Pregnant dams were infused with nicotine (6 mg/kg/day) subcutaneously from the third day of pregnancy until birth. Results indicate that prenatal nicotine exposure leads to increased anxiety and depressive-like effects and impaired spatial memory. Synaptic plasticity in the form of long-term potentiation (LTP), basal synaptic transmission, and AMPA receptor-mediated synaptic currents were reduced. The deficit in synaptic plasticity was paralleled by declines in protein levels of vesicular glutamate transporter 1 (VGLUT1), synaptophysin, AMPA receptor subunit GluR1, phospho(Ser845) GluR1, and postsynaptic density 95 (PSD-95). These results suggest that prenatal nicotine exposure by maternal smoking could result in alterations in the glutamatergic system in the hippocampus contributing to the abnormal neurobehavioral outcomes.

Maternal smoking during pregnancy and offspring brain structure and function: review and agenda for future research

INTRODUCTION

Maternal smoking during pregnancy (MSDP) has been associated with long-term neurobehavioral and cognitive deficits in offspring. Animal models demonstrate alterations in brain structure and function following prenatal nicotine exposure. However, few studies have assessed the relationship between MSDP and brain development in humans. Therefore, the aims of this review are (a) to synthesize findings from the small number of human studies investigating effects of MSDP on offspring brain development and (b) to outline an agenda for future research in this nascent area.

METHODS

We searched MEDLINE and Psychinfo databases for human studies of MSDP and offspring brain structure and/or function.

RESULTS

Eleven studies meeting our search criteria were identified; 6 studies investigated effects of MSDP on brain structure; 5 examined effects on brain function. Across studies, MSDP was associated with decreased volume/thickness of the cerebellum and corpus callosum, increased auditory brainstem responses, and lack of coordination across brain regions during information and auditory processing.

CONCLUSIONS

Results from the small number of human studies revealed effects of MSDP on brain structure and function, highlighting potential neural pathways linking MSDP and offspring neurobehavioral and cognitive deficits. Given the limited amount of research in this area, we propose an agenda for future research. Gold standard studies would utilize longitudinal designs, integrated biological and maternal report measures of MSDP, and repeated measures of brain structure/function and neurobehavioral deficits across key developmental periods.

The effects of galantamine on nicotine withdrawal-induced deficits in contextual fear conditioning in C57BL/6 mice

Current smoking cessation aids are relatively ineffective at maintaining abstinence during withdrawal. Nicotine withdrawal is associated with a variety of symptoms including cognitive deficits and targeting these deficits may be a useful strategy for maintaining abstinence. Galantamine is an acetylcholinesterase inhibitor and allosteric modulator of nicotinic acetylcholine receptors (nAChRs) with cognitive enhancing effects that may alleviate cognitive deficits associated with nicotine withdrawal. The effects of galantamine on nicotine withdrawal-induced deficits in contextual fear conditioning in C57BL/6 mice were examined. An initial acute dose-response experiment revealed that 0.5 and 1mg/kg galantamine had no effect on fear conditioning. To determine if galantamine would reverse nicotine withdrawal-related deficits in contextual fear conditioning, mice were implanted with osmotic mini-pumps that delivered chronic saline or 6.3mg/kg/d nicotine for 12 days and then pumps were removed. Training and testing of fear conditioning occurred 24 and 48 h later, respectively. Nicotine withdrawal disrupted contextual fear conditioning, which was reversed with 1 but not 0.5mg/kg galantamine. Across all conditions in both studies 2mg/kg galantamine led to high levels of freezing that were likely due to nonspecific effects. The ability of galantamine to reverse nicotine withdrawal-deficits in contextual conditioning is likely mediated through enhanced levels of acetylcholine via inhibition of acetylcholinesterase, potentiation of hippocampal α4β2* nAChRs, or both. The present study suggests that acetylcholinesterase inhibitors and/or drugs that act as allosteric modulators of nAChRs might be targets for smoking cessation aids because they may alleviate withdrawal symptoms such as cognitive deficits that can lead to relapse.

Prenatal IV nicotine exposure produces a sex difference in sensorimotor gating of the auditory startle reflex in adult rats

Maternal smoking during pregnancy is associated with auditory processing deficits in children; these effects have been confirmed with animal models of continuous high-dose prenatal nicotine exposure. The present experiments utilized a novel, low-dose, intermittent, intravenous (IV) gestational nicotine exposure model to investigate potential deficits on the preattentive process of sensorimotor gating, as indexed by prepulse inhibition (PPI), in preweanling and adult rat offspring. Pregnant dams received bolus IV injections of nicotine (0.05 mg/kg/injection) 3×/day on gestational days 8-21. Auditory and tactile stimulus modalities were probed with tone and air puff prepulse stimuli, respectively. These prepulse stimuli preceded a 100 dB(A) startle tone by six different interstimulus intervals (ISIs; 0, 8, 40, 80, 120, 4000 ms) to define a curve of response inhibition. The magnitude of PPI increased with age, from 59 to 81% inhibition. Preweanlings (PNDs 14 and 18) and adults (PND 75) gestationally exposed to nicotine exhibited altered startle responding relative to controls, but the nature of the deficit became more localized at later ages. The entire curve of response inhibition in preweanlings exposed to prenatal nicotine (PND 14) was shifted up relative to controls, and notably, did not interact with prepulse stimulus modality, suggesting a generalized increased sensorimotor responsiveness as a function of prenatal nicotine. At PND 18, a shift in the response curve across all ISIs was again noted, but varied as a function of prepulse stimulus modality; the increased sensorimotor responsiveness was specific to the auditory, but not tactile, sensory modality. In adulthood, male and female animals prenatally exposed to nicotine were differentially sensitive to modulation by the ISIs, relative to control male and female animals. Specifically, despite robust PPI, adult females exposed to gestational nicotine were relatively insensitive to changes in ISI from 8 to 120 ms; in contrast, the robust PPI of nicotine-exposed males demonstrated a clear focal point of inhibition at 40 ms. These findings indicate that a low, daily dosing of IV prenatal nicotine produces long-lasting alterations in auditory PPI. An important implication of this research is that "chipping" with smoked-tobacco products during pregnancy may produce enduring changes in sensorimotor processing.

Prenatal cigarette exposure and infant learning stimulation as predictors of cognitive control in childhood

Prenatal exposures to neurotoxins and postnatal parenting practices have been shown to independently predict variations in the cognitive development and emotional-behavioral well-being of infants and children. We examined the independent contributions of prenatal cigarette exposure and infant learning stimulation, as well as their inter-relationships in predicting variations in the proficiency of executive attention, a core element of cognitive control and self-regulation. Participants were an ethnic-racially, socio-economically diverse sample of 249 children followed from birth in the Project on Human Development in Chicago Neighborhoods. We obtained histories of prenatal exposure to alcohol, cigarettes, and other drugs, and we assessed socio-economic status and learning stimulation during a home visit when the participants were infants. In childhood we utilized the Attention Networks Test to assess the proficiency of executive attention during two home visits, one year apart. Accounting for age, SES, prenatal alcohol exposure, and baseline performance, we found that prenatal cigarette exposure impaired the speed of executive attention. Infant learning stimulation mitigated these effects, and predicted better accuracy of executive attention as well, suggestive of both protective and health promoting effects. Effect sizes for these relations, whether examined independently or by their inter-relationships, were comparable to if not greater in magnitude than the effects of age on speed and accuracy, highlighting the importance of these very early experiences in shaping the proficiency of self-regulation. Since executive attention is central to cognitive control and self-regulation, previously described relations between prenatal cigarette exposure, parenting practices, and some forms of childhood psychopathology may be contingent on how early learning stimulation contributes to the proficiency of executive attention through direct and indirect effects. Furthermore, considering the prolonged developmental trajectory of executive attention, interventions to support provision of learning stimulation may mitigate poor outcomes for some at-risk children by promoting development of more proficient executive attention.

Prenatal tobacco exposure: developmental outcomes in the neonatal period

Smoking during pregnancy is a persistent public health problem that has been linked to later adverse outcomes. The neonatal period--the first month of life--carries substantial developmental change in regulatory skills and is the period when tobacco metabolites are cleared physiologically. Studies to date mostly have used cross-sectional designs that limit characterizing potential impacts of prenatal tobacco exposure on the development of key self-regulatory processes and cannot disentangle short-term withdrawal effects from residual exposure-related impacts. In this study, pregnant participants (N = 304) were recruited prospectively during pregnancy, and smoking was measured at multiple time points, with both self-report and biochemical measures. Neonatal attention, irritable reactivity, and stress dysregulation were examined longitudinally at three time points during the first month of life, and physical growth indices were measured at birth. Tobacco-exposed infants showed significantly poorer attention skills after birth, and the magnitude of the difference between exposed and nonexposed groups attenuated across the neonatal period. In contrast, exposure-related differences in irritable reactivity largely were not evident across the 1st month of life, differing marginally at 4 weeks of age only. Third-trimester smoking was associated with pervasive, deleterious, dose–response impacts on physical growth measured at birth, whereas nearly all smoking indicators throughout pregnancy predicted level and growth rates of early attention. The observed neonatal pattern is consistent with the neurobiology of tobacco on the developing nervous system and fits with developmental vulnerabilities observed later in life.

Nicotinic receptor gene CHRNA4 interacts with processing load in attention

BACKGROUND

Pharmacological studies suggest that cholinergic neurotransmission mediates increases in attentional effort in response to high processing load during attention demanding tasks [1].

METHODOLOGY/PRINCIPAL FINDINGS

In the present study we tested whether individual variation in CHRNA4, a gene coding for a subcomponent in α4β2 nicotinic receptors in the human brain, interacted with processing load in multiple-object tracking (MOT) and visual search (VS). We hypothesized that the impact of genotype would increase with greater processing load in the MOT task. Similarly, we predicted that genotype would influence performance under high but not low load in the VS task. Two hundred and two healthy persons (age range  =  39-77, Mean  =  57.5, SD  =  9.4) performed the MOT task in which twelve identical circular objects moved about the display in an independent and unpredictable manner. Two to six objects were designated as targets and the remaining objects were distracters. The same observers also performed a visual search for a target letter (i.e. X or Z) presented together with five non-targets while ignoring centrally presented distracters (i.e. X, Z, or L). Targets differed from non-targets by a unique feature in the low load condition, whereas they shared features in the high load condition. CHRNA4 genotype interacted with processing load in both tasks. Homozygotes for the T allele (N  =  62) had better tracking capacity in the MOT task and identified targets faster in the high load trials of the VS task.

CONCLUSION

The results support the hypothesis that the cholinergic system modulates attentional effort, and that common genetic variation can be used to study the molecular biology of cognition.

Cortico-thalamic connectivity is vulnerable to nicotine exposure during early postnatal development through α4/β2/α5 nicotinic acetylcholine receptors

Tobacco smoke exposure during development can result in lasting alterations in sensory processing and attention. This suggests that some constituent of smoke, such as the primary addictive component, nicotine, alters neurodevelopment. Although many effects of developmental nicotine exposure have been identified in humans and animal models, very few mechanistic studies have identified the molecular and anatomical basis for a defined behavioral consequence of developmental exposure. We show in this study that a mouse model of developmental nicotine exposure results in hypersensitive passive avoidance in adulthood. We have used transgenic mice in which β2 subunit containing nicotinic acetylcholine receptors (β2* nAChRs) are expressed exclusively on corticothalamic neurons (β2 tr(CT) mice) to identify the receptor subtypes involved and also to define the circuit level site of action responsible for this persistent, nicotine-induced behavioral phenotype. Further characterization of the native nAChRs expressed in this circuit indicates that both (α4)(2)(β2)(3) and (α4)(2)(β2)(2)α5 nAChR subtypes are present in corticothalamic projections. Consistent with a role for (α4)(2)(β2)(2)α5 nAChRs in mediating the effect of developmental nicotine exposure on adult passive avoidance behavior, constitutive deletion of the α5 nAChR subunit also alters this behavior. A critical period for this developmental consequence of nicotine exposure was defined by limiting exposure to the early post-natal period. Taken together, these studies identify a novel consequence of developmental nicotine exposure in the mouse, define the nAChR subtypes and neural circuit involved in this behavioral change and delimit the neurodevelopmental period critical for vulnerability to a behavioral alteration that persists into adulthood.

Effects of prenatal tobacco, alcohol and marijuana exposure on processing speed, visual-motor coordination, and interhemispheric transfer

Deficits in motor control are often reported in children with prenatal alcohol exposure (PAE). Less is known about the effects of prenatal tobacco exposure (PTE) and prenatal marijuana exposure (PME) on motor coordination, and previous studies have not considered whether PTE, PAE, and PME interact to affect motor control. This study investigated the effects of PTE, PAE, and PME as well as current drug use on speed of processing, visual-motor coordination, and interhemispheric transfer in 16-year-old adolescents. Data were collected as part of the Maternal Health Practices and Child Development Project. Adolescents (age 16, n=320) participating in a longitudinal study of the effects of prenatal substance exposure on developmental outcomes were evaluated in this study. The computerized Bimanual Coordination Test (BCT) was used to assess each domain of function. Other important variables, such as demographics, home environment, and psychological characteristics of the mother and adolescent were also considered in the analyses. There were significant and independent effects of PTE, PAE, and PME on processing speed and interhemispheric transfer of information. PTE and PME were associated with deficits in visual-motor coordination. There were no interactions between PAE, PTE, and PME. Current tobacco use predicted deficits in speed of processing. Current alcohol and marijuana use by the offspring were not associated with any measures of performance on the BCT.

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.

Smoking abstinence and reinstatement effects in adolescent cigarette smokers

INTRODUCTION

The study objectives were to examine smoking abstinence and reinstatement effects on subjective experience and cognitive performance among adolescent smokers.

METHODS

Adolescents (aged 14-17 years, 60 daily smokers and 32 nonsmokers) participated. Participants completed baseline assessments (Session 1) and returned to the laboratory 1-3 days later to repeat assessments (Session 2); half of the smokers were randomly assigned to 15-17 hr tobacco abstinence preceding Session 2.

RESULTS

During Session 2, abstaining smokers reported significantly greater increases in withdrawal symptoms, smoking urges, and negative affect compared with smokers who did not abstain and compared with nonsmokers. Smoking reinstatement reversed abstinence effects, returning to baseline levels for smoking urges and negative affect. Abstaining smokers showed significantly enhanced cognitive performance on two of six tasks (two-letter search compared with nonabstaining smokers; serial reaction time compared with nonsmokers); smoking reinstatement resulted in significant decrements on these two tasks relative to nonabstaining smokers.

DISCUSSION

Effects of smoking abstinence and reinstatement on self-report measures are consistent with earlier research with adolescent as well as adult smokers and may help to elucidate the motivational underpinnings of smoking maintenance among adolescent smokers. Effects found on cognitive performance were contrary to hypotheses; further research is needed to understand better the role of cognitive performance effects in smoking maintenance among adolescents.

Tobacco smoking produces widespread dominant brain wave alpha frequency increases

The major pharmacological ingredient in tobacco smoke is nicotine, a mild stimulant known to alter brain electrical activity. The objective of this study was to determine if tobacco smoking in humans produces localized or widespread neocortical dominant alpha electroencephalographic (EEG) frequency increases consistent with nicotine stimulation of the brainstem activating system in animals. Twenty-two male volunteer non-deprived tobacco smokers were studied. They were asked not to smoke for at least 1h before the experiment in mid-morning as part of their usual smoking schedule. In the laboratory, they sham smoked and then smoked their favorite tobacco cigarette. Two experimental sessions (#1 and #2) were conducted, separated by a one to two month interval. In both sessions, there were minor statistically significant increases in the dominant alpha frequencies after sham smoking. In both sessions, after the subjects smoked a favorite tobacco cigarette there was a significant generalized increase in dominant alpha EEG frequencies in most scalp recording sites. This study demonstrates that tobacco smoking produces widespread bilateral neocortical increases in dominant alpha EEG frequencies consistent with the stimulant effects of nicotine on the brainstem reticular activating system.

Neuroimaging of children following prenatal drug exposure

Recent advances in MR-based brain imaging methods have provided unprecedented capabilities to visualize the brain. Application of these methods has allowed identification of brain structures and patterns of functional activation altered in offspring of mothers who used licit (e.g., alcohol and tobacco) and illicit (e.g., cocaine, methamphetamine, and marijuana) drugs during pregnancy. Here we review that literature, which though somewhat limited by the complexities of separating the specific effects of each drug from other confounding variables, points to sets of interconnected brain structures as being altered following prenatal exposure to drugs of abuse. In particular, dopamine-rich cortical (e.g., frontal cortex) and subcortical (e.g., basal ganglia) fetal brain structures show evidence of vulnerability to intrauterine drug exposure suggesting that during brain development drugs of abuse share a specific profile of developmental neurotoxicity. Such brain malformations may shed light on mechanisms underlying prenatal drug-induced brain injury, may serve as bio-markers of significant intrauterine drug exposure, and may additionally be predictors of subsequent neuro-developmental compromise. Wider clinical use of these research-based non-invasive methods will allow for improved diagnosis and allocation of therapeutic resources for affected infants, children, and young adults.

Allelic variation of calsyntenin 2 (CLSTN2) modulates the impact of developmental tobacco smoke exposure on mnemonic processing in adolescents

BACKGROUND

Exposure to nicotine in tobacco smoke during development has been linked to subsequent deficits in attention and memory. The present study tested for evidence that genetic variation may contribute to individual differences in vulnerability to the effects of developmental exposure to tobacco smoke on memory and medial temporal lobe function in adolescents.

METHODS

Verbal and visuospatial memory were assessed and functional magnetic resonance imaging (fMRI) data were acquired in 101 adolescents systematically characterized for prenatal and adolescent exposure to tobacco smoke, while they performed an encoding and recognition memory task. The impact of allelic variation at loci within CLSTN2 (encoding synaptic protein calsyntenin 2) and KIBRA, shown previously to modulate early and delayed recall of words, on the dependent measures was examined.

RESULTS

KIBRA genotype did not exert significant main or interacting effects with prenatal or adolescent exposure to tobacco smoke on verbal or visuospatial memory. Previous observations of a beneficial effect of the CLSTN2 C allele on verbal recall were replicated. Adolescent exposure to tobacco smoke reversed this beneficial effect and was associated with increased activation of parahippocampal gyrus during early and delayed recognition in CLTSN2 C allele carriers. While the CLSTN2 C allele conferred enhanced functional connectivity between brain regions subserving accurate verbal recognition, adolescent exposure to tobacco smoke reversed this effect.

CONCLUSIONS

These findings extend previous work demonstrating that calsyntenins play an essential role in learning and indicate that this role is modulated both by CLSTN2 genotype and, during adolescent development, by exposure to tobacco smoke.

The dynamic effects of nicotine on the developing brain

Nicotinic acetylcholine receptors (nAChRs) regulate critical aspects of brain maturation during the prenatal, early postnatal, and adolescent periods. During these developmental windows, nAChRs are often transiently upregulated or change subunit composition in those neural structures that are undergoing major phases of differentiation and synaptogenesis, and are sensitive to environmental stimuli. Nicotine exposure, most often via tobacco smoke, but increasingly via nicotine replacement therapy, has been shown to have unique effects on the developing human brain. Consistent with a dynamic developmental role for acetylcholine, exogenous nicotine produces effects that are unique to the period of exposure and that impact the developing structures regulated by acetylcholine at that time. Here we present a review of the evidence, available from both the clinical literature and preclinical animal models, which suggests that the diverse effects of nicotine exposure are best evaluated in the context of regional and temporal expression patterns of nAChRs during sensitive maturational periods, and disruption of the normal developmental influences of acetylcholine. We present evidence that nicotine interferes with catecholamine and brainstem autonomic nuclei development during the prenatal period of the rodent (equivalent to first and second trimester of the human), alters the neocortex, hippocampus, and cerebellum during the early postnatal period (third trimester of the human), and influences limbic system and late monoamine maturation during adolescence.

Predictors of starting to smoke cigarettes in patients with first episode psychosis

INTRODUCTION

Cigarette smoking is common in psychotic disorders and may be initiated in an attempt to control features of illness. However, genetic, obstetric and early life conditions are risks for starting to smoke in the general population but their role in psychotic patients is unclear.

METHOD

Smoking history and the putative predictors of starting to smoke were assessed in a community-wide sample of 115 first episode psychosis patients. The proportion that initiated smoking was compared with that from population surveys and the impact of risk factors was assessed within the patient sample.

RESULTS

Most patients began smoking before illness onset and the proportion who initiated smoking was significantly high by the onset of a functional decline. Gestational tobacco exposure was a risk for smoking and was also associated with low birthweight, poor academic achievement, and obesity. Low familial socioeconomic position but not familial psychiatric problems also predicted smoking initiation.

DISCUSSION

In most cases, smoking preceded illness onset and was not a response to early features of illness. General population predictors of starting to smoke were also associated with smoking initiation in psychotic patients. Of these risks, exposure to tobacco during gestation is noteworthy in that it affects brain development and is associated with cognitive, behavioral, psychiatric and general health problems. In addition, nicotine interacts with other substances of abuse. The initiation of smoking before illness onset and the association with developmental problems raises the question of whether cigarette smoking influences some aspects of illness in patients with psychosis.

Predictors of early abstinence in smokers with schizophrenia

BACKGROUND

In patients with schizophrenia, the smoking cessation rate is low and the burden of smoking-related morbidity and mortality is high. Identification of factors associated with abstinence may allow clinicians to optimize treatment prior to a smoking cessation attempt.

METHOD

To identify factors associated with successful smoking cessation in patients with a DSM-IV diagnosis of schizophrenia, we analyzed baseline data from 114 stable outpatient smokers with schizophrenia who participated in 1 of 2 smoking cessation trials. The outcome of interest was 4 weeks' continuous abstinence at the end of a 12-week nicotine dependence treatment intervention. Baseline factors associated with abstinence were identified with univariate methods and entered into a manual, forward-selection multivariable regression model to identify independent predictors of abstinence. The study was conducted from March 1999 to February 2004.

RESULTS

Fourteen of 114 participants (12%) had biochemically verified 4 weeks' continuous abstinence at week 12. We included 10 noncorrelated variables with a univariate association with abstinence in a multivariable model, controlling for pharmacotherapy, age, and gender. Age at initiation of smoking and baseline variability in attentiveness, as measured by Continuous Performance Test-AX (CPT-AX) hit reaction time standard error, were independently associated with abstinence. For every year increase in age at initiation of smoking, the OR for abstinence was 1.36 (95% CI = 1.01 to 1.83), p = .048. For every millisecond decrease in the variability of the reaction time of CPT-AX, the OR for achieving abstinence was 1.55 (95% CI = 1.07 to 2.24), p = .021.

CONCLUSION

Later initiation of smoking was associated with increased and baseline attentional impairment with reduced odds of abstinence. Additional research to further our understanding of the relationship between attentional impairment and cigarette smoking in schizophrenia may lead to improved nicotine dependence treatments for this group.

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

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

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.

Neuroimaging, genetics and the treatment of nicotine addiction

Advances in neuroimaging and genomics provide an unprecedented opportunity to accelerate medication development for nicotine dependence and other addictions. Neuroimaging studies have begun to elucidate the functional neuroanatomy and neurochemistry underlying effects of nicotine and nicotine abstinence. In parallel, genetic studies, including both candidate gene and genome-wide association approaches, are identifying key neurobiological targets and pathways important in addiction to nicotine. To date, only a few neuroimaging studies have explored effects of nicotine or abstinence on brain activity as a function of genotype. Most analyses of genotype are retrospective, resulting in small sample sizes for testing effects of the minor alleles for candidate genes. The purpose of this review is to provide an outline of the work in neuroimaging, genetics, and nicotine dependence, and to explore the potential for increased integration of these approaches to improve nicotine dependence treatment.

Nicotine and brain development

Preclinical studies, using primarily rodent models, have shown acetylcholine to have a critical role in brain maturation via activation of nicotinic acetylcholine receptors (nAChRs), a structurally diverse family of ligand-gated ion channels. nAChRs are widely expressed in fetal central nervous system, with transient upregulation in numerous brain regions during critical developmental periods. Activation of nAChRs can have varied developmental influences that are dependent on the pharmacologic properties and localization of the receptor. These include regulation of transmitter release, gene expression, neurite outgrowth, cell survival, and synapse formation and maturation. Aberrant exposure of fetal and neonatal brain to nicotine, through maternal smoking or nicotine replacement therapy (NRT), has been shown to have detrimental effects on cholinergic modulation of brain development. These include alterations in sexual differentiation of the brain, and in cell survival and synaptogenesis. Long-term alterations in the functional status and pharmacologic properties of nAChRs may also occur, which result in modifications of specific neural circuitry such as the brainstem cardiorespiratory network and sensory thalamocortical gating. Such alterations in brain structure and function may contribute to clinically characterized deficits that result from maternal smoking, such as sudden infant death syndrome and auditory-cognitive dysfunction. Although not the only constituent of tobacco smoke, there is now abundant evidence that nicotine is a neural teratogen. Thus, alternatives to NRT should be sought as tobacco cessation treatments in pregnant women.

Prenatal exposure to maternal cigarette smoking and the adolescent cerebral cortex

Smoking during pregnancy is associated with long-term consequences on offspring behavior. We measured thickness of the cerebral cortex using magnetic resonance images obtained in 155 adolescents exposed in utero to maternal smoking and compared them with 159 non-exposed subjects matched by maternal education. Orbitofrontal, middle frontal, and parahippocampal cortices were thinner in exposed, as compared with non-exposed, individuals; these differences were more pronounced in female adolescents. In exposed females, the thickness of the orbitofrontal cortex correlated negatively with a self-rated assessment of caring, one of the components of a model of positive youth development. These findings provide evidence of the long-term impact of prenatal environment on a neural substrate of cognition and social behavior.

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.

Corpus callosum in adolescent offspring exposed prenatally to maternal cigarette smoking

Teratogens, such as alcohol or anti-epileptic drugs, affect the size of the corpus callosum. Here we report findings obtained in a case-control study that investigated possible effects of teratogens contained in cigarette smoke on the size and structural properties of this structure. We recruited and scanned with magnetic resonance imaging a total of 408 adolescents (12 to 18 years of age); a subsample of 300 adolescents is considered in this report. Cases (n=146) were exposed to maternal cigarette smoking during pregnancy; non-exposed controls (n=154) were matched to cases by maternal education. We measured the size of corpus callosum (CC) and its sections (corrected for brain size), as well as mean values of magnetization-transfer ratio (MTR) in each CC section. Corpus callosum, and especially its posterior part, was smaller in the exposed vs. non-exposed female adolescents; no significant effects were found in males. Exposed and non-exposed subjects did not differ in the MTR-based index of myelination in either gender in any CC section. Given the lack of exposure effect on the myelination index, this finding might reflect a lower number of inter-hemispheric connections in female offspring of mothers who smoked during pregnancy.