Gestational exposure to nicotine in drinking water: teratogenic effects and methodological issues

Sex Differences in the Behavioural Outcomes of Prenatal Nicotine and Tobacco Exposure

Smoking remains the leading cause of preventable death worldwide. A combination of biological and environmental risk factors make women especially vulnerable to nicotine addiction, making it harder for them to quit smoking. Smoking during pregnancy, therefore, is still a major health concern, with epidemiological data suggesting a role for gestational nicotine exposure in the development of several behavioural disorders. Given there are significant sex-specific behavioural outcomes related to smoking in adolescence and adulthood, it is probable that the behavioural outcomes following gestational nicotine or tobacco exposure are similarly sex-dependent. This is an especially relevant topic as the current landscape of nicotine use shifts toward vaping, a mode of high doses of nicotine delivery that is largely believed to be a safer alternative to cigarettes among the public as well as among pregnant women. Here we review existing clinical and preclinical findings regarding the sex-dependent behavioural outcomes of prenatal nicotine exposure. We also highlight the challenges within this literature, particularly those areas in which further research is necessary to improve consistency within, and between, clinical and preclinical findings.

Distinct sex-dependent effects of maternal preconception nicotine and enrichment on the early development of rat offspring brain and behavior

Developmental nicotine exposure is harmful to offspring. Whereas much is known about the consequences of prenatal nicotine exposure, relatively little is understood about how maternal preconception nicotine impacts the next generation. Positive experiences, such as environmental enrichment/complexity, have considerable potential to improve developmental outcomes and even treat and prevent drug addiction. Therefore, the current study sought to identify how maternal exposure to moderate levels of nicotine prior to conception impacts offspring development, and if the presumably negative consequence of nicotine could be reversed by concurrent exposure to an enriched environment. We treated female Long Evans rats with nicotine in their drinking water (15 mg nicotine salt/L) for seven weeks while residing in either standard or enriched conditions. Both experiences occurred exclusively prior to mating. Nicotine exposure reduced dam fertility by ~20% (p = .06). Females reared their own litters, and offspring were tested in two assessments of early development: negative geotaxis and open field. Offspring were euthanized at weaning (P21), and their brains were processed with Golgi-Cox solution to allow quantification of dendritic spine density. Results indicate that neither maternal nicotine or enrichment had an impact on maternal care, but male offspring were impaired at negative geotaxis due to maternal nicotine, female offspring showed altered open field exploration due to maternal enrichment, and offspring of both sexes had increased spine density in OFC due to maternal enrichment. Therefore, this experiment provides novel insights into the unique, sex-dependent consequences of maternal preconception nicotine and enrichment on the early development of rat behavior and brain.

Diabetes, Oxidative Stress, and DNA Damage Modulate Cranial Neural Crest Cell Development and the Phenotype Variability of Craniofacial Disorders

Craniofacial malformations are among the most common birth defects in humans and they often have significant detrimental functional, aesthetic, and social consequences. To date, more than 700 distinct craniofacial disorders have been described. However, the genetic, environmental, and developmental origins of most of these conditions remain to be determined. This gap in our knowledge is hampered in part by the tremendous phenotypic diversity evident in craniofacial syndromes but is also due to our limited understanding of the signals and mechanisms governing normal craniofacial development and variation. The principles of Mendelian inheritance have uncovered the etiology of relatively few complex craniofacial traits and consequently, the variability of craniofacial syndromes and phenotypes both within families and between families is often attributed to variable gene expression and incomplete penetrance. However, it is becoming increasingly apparent that phenotypic variation is often the result of combinatorial genetic and non-genetic factors. Major non-genetic factors include environmental effectors such as pregestational maternal diabetes, which is well-known to increase the risk of craniofacial birth defects. The hyperglycemia characteristic of diabetes causes oxidative stress which in turn can result in genotoxic stress, DNA damage, metabolic alterations, and subsequently perturbed embryogenesis. In this review we explore the importance of gene-environment associations involving diabetes, oxidative stress, and DNA damage during cranial neural crest cell development, which may underpin the phenotypic variability observed in specific craniofacial syndromes.

Prenatal cigarette smoke exposure slightly alters neurobehavioral development in neonatal rats: Implications for developmental origins of health and disease (DoHAD)

Numerous studies indicate that smoking during pregnancy exerts harmful effects on fetal brain development. The aim of this study was to determine the influence of maternal smoking during pregnancy on the early physical and neurobehavioral development of newborn rats. Wistar rats were subjected to whole-body smoke exposure for 2 × 40 min daily from the day of mating until day of delivery. For this treatment, a manual closed-chamber smoking system and 4 research cigarettes per occasion were used. After delivery the offspring were tested daily for somatic growth, maturation of facial characteristics and neurobehavioral development until three weeks of age. Motor coordination tests were performed at 3 and 4 weeks of age. We found that prenatal cigarette smoke exposure did not alter weight gain or motor coordination. Critical physical reflexes indicative of neurobehavioral development (eyelid reflex, ear unfolding) appeared significantly later in pups prenatally exposed to smoke as compared to the control group. Prenatal smoke exposure also resulted in a delayed appearance of reflexes indicating neural maturity, including hind limb grasping and forelimb placing reflexes. In conclusion, clinically relevant prenatal exposure to cigarette smoke results in slightly altered neurobehavioral development in rat pups. These findings suggest that chronic exposure of pregnant mothers to cigarette smoke (including passive smoking) results in persisting alterations in the developing brain, which may have long-lasting consequences supporting the concept of developmental origins of health and disease (DoHAD).

Cellular and Molecular Changes in Hippocampal Glutamate Signaling and Alterations in Learning, Attention, and Impulsivity Following Prenatal Nicotine Exposure

Over 70 million European pregnant women are smokers during their child-bearing years. Consumption of tobacco-containing products during pregnancy is associated with several negative behavioral outcomes for the offspring, including a higher susceptibility for the development of attention-deficit/hyperactive disorder (ADHD). In efforts to minimize fetal exposure to tobacco smoke, many women around the world switch to nicotine replacement therapies (NRTs) during the gestational period; however, prenatal nicotine exposure (PNE) in any form has been associated with alterations in cognitive processes, including learning, memory, and attention. These processes are controlled by glutamatergic signaling of hippocampal pyramidal neurons within the CA1 region, suggesting actions of nicotine on glutamatergic transmission in this region if present prenatally. Accordingly, we aimed to investigate hippocampal glutamatergic function following PNE treatment in NMRI mice employing molecular, cellular electrophysiology, and pharmacological approaches, as well as to evaluate cognition in the rodent continuous performance task (rCPT), a recently developed mouse task allowing assessment of learning, attention, and impulsivity. PNE induced increases in the expression levels of mRNA coding for different glutamate receptors and subunits within the hippocampus. Functional alterations in AMPA and NMDA receptors on CA1 pyramidal neurons of PNE mice were suggestive of higher GluA2-lacking and lower GluN2A-containing receptors, respectively. Finally, PNE was associated with reduced learning, attention, and enhanced impulsivity in the rCPT. Alterations in glutamatergic functioning in CA1 neurons parallel changes seen in the spontaneously hypertensive rat ADHD model and likely contribute to the lower cognitive performance in the rCPT.

Gestational caloric restriction with micronutrients supplementation does not delay development and promotes feeding behavior benefits

Introduction: Caloric restriction (CR) has been proven to promote a series of health benefits from yeast to primates. Nowadays, increasing rates of obesity certainly encourage researchers to evaluate CR effects and establish it as a therapeutic approach. Maternal obesity is also a concern, and studies in the developmental origins of health and disease (DOHaD) have shown the importance of interventions during pregnancy, especially those involving maternal nutrition. On the other hand, undernutrition during pregnancy leads to increased weight gain, disturbed feeding behavior and dysfunctional metabolism in adulthood.Methods: In this way, we utilized moderate CR (20% compared to control consumption) in pregnant Wistar rats as intervention, with malnutrition control by micronutrients supplementation. We assessed CR effects on offspring's developmental milestones, feeding behavior, exploratory behavior, and memory on adolescence (PND21) and adulthood (PND60).Results: We did not find alterations on litter size or birth weight, although CR pups were leaner at adult ages. Importantly, no delay in development was observed. Besides, female pups showed earlier suction reflex and male pups showed earlier response to the negative geotaxis. CR pups also showed less preference for palatable food (Froot Loops®) at adult age, which could be decisive on obesity tendency. Locomotor activity was increased by CR on PND60 and there was no effect on memory at all.Discussion: Our results on development and behavior demonstrate that gestational CR may be a helpful health strategy if malnutrition is well controlled, with potential clinical impact.

Developmental toxicity of e-cigarette aerosols

Maternal smoking during pregnancy represents a major public health concern increasing the risk for low birth weight, congenital anomalies, preterm birth, fetal mortality, and morbidity. In an effort to diminish adverse developmental effects of exposure to cigarette smoking, pregnant women, and women of reproductive age, are increasingly turning to electronic nicotine delivery systems (ENDS), such as e-cigarettes, as an alternative. Given that health risks associated with ENDS use during pregnancy are largely unknown, there is an acute need to determine risks vs. benefits of e-cigarette use by pregnant women. While the most recent Surgeon General's Report on the "Health Consequences of Smoking" states that "the evidence is sufficient to infer that nicotine adversely affects maternal and fetal health during pregnancy, contributing to multiple adverse outcomes," it remains unclear whether use of ENDS represents a "safer alternative" to tobacco smoking during pregnancy. This is due, in part, to the lack of sufficient and conclusive evidence concerning whether or not maternal e-cigarette use adversely affects embryonic/fetal development. While several recent developmental studies have challenged the safety of nicotine inhalation via ENDS, the true risks of smoking e-cigarettes during the first trimester of pregnancy-the period of organogenesis-are largely unknown. Moreover, evidence is emerging that even nicotine-free e-cigarette aerosols may harm the developing conceptus, suggesting that components of e-cigarette liquid, including flavorings, may be developmentally toxicity. Focused human epidemiological analyses, and carefully designed animal studies are critically needed to address the question of the safety of ENDS use during pregnancy.

Perinatal nicotine exposure impairs learning of a skilled forelimb reaching task in male but not female adult mice

Developmental tobacco or nicotine exposure is associated with various adverse outcomes in human and preclinical studies, respectively. For example, perinatal nicotine exposure in mice causes morphologic changes in neurons across sensory and motor cortices and results in impairments in sensory learning. However, the effects of developmental nicotine exposure on motor learning have not been reported. To determine whether nicotine-induced changes in behavior extend to motor tasks, we provided female C57Bl/6 dams with nicotine drinking water (200 μg/ml in 2% saccharin), or vehicle (2% saccharin), a standard paradigm to expose pups to nicotine in utero and postnatally through lactation. Male and female pups were subsequently tested in adulthood in a single-pellet reaching task with millet seeds, and also tested for gross motor function and feeding behavior. We found that male, but not female, mice exposed to nicotine throughout early development demonstrated impaired learning of single-seed reaching. Nicotine-treated animals did not differ from control animals in gross motor performance or millet seed intake, although female mice consumed more millet seeds than male mice when reaching was not required. These studies show that nicotine exposure during development can impair behavior in a skilled motor task that depends on cortical synaptic plasticity, and that this effect is sex-dependent.

Prenatal nicotine exposure decreases the release of dopamine in the medial frontal cortex and induces atomoxetine-responsive neurobehavioral deficits in mice

Increased risk of attention-deficit/hyperactivity disorder (AD/HD) is partly associated with the early developmental exposure to nicotine in tobacco smoke. Emerging reports link tobacco smoke exposure or prenatal nicotine exposure (PNE) with AD/HD-like behaviors in rodent models. We have previously reported that PNE induces cognitive behavioral deficits in offspring and decreases the contents of dopamine (DA) and its turnover in the prefrontal cortex (PFC) of offspring It is well known that the dysfunction of DAergic system in the brain is one of the core factors in the pathophysiology of AD/HD. Therefore, we examined whether the effects of PNE on the DAergic system underlie the AD/HD-related behavioral changes in mouse offspring. PNE reduced the release of DA in the medial PFC (mPFC) in mouse offspring. PNE reduced the number of tyrosine hydroxylase (TH)-positive varicosities in the mPFC and in the core as well as the shell of nucleus accumbens, but not in the striatum. PNE also induced behavioral deficits in cliff avoidance, object-based attention, and sensorimotor gating in offspring. These behavioral deficits were attenuated by acute treatment with atomoxetine (3 mg/kg, s.c.) or partially attenuated by acute treatment with MPH (1 mg/kg, s.c.). Taken together, our findings support the notion that PNE induces neurobehavioral abnormalities in mouse offspring by disrupting the DAergic system and improve our understanding about the incidence of AD/HD in children whose mothers were exposed to nicotine during their pregnancy.

Prenatal Nicotine Exposure Impairs Executive Control Signals in Medial Prefrontal Cortex

Prenatal nicotine exposure (PNE) is linked to numerous psychiatric disorders including attention deficit hyperactivity disorder (ADHD). Current literature suggests that core deficits observed in ADHD reflect abnormal inhibitory control governed by the prefrontal cortex. Yet, it is unclear how neural activity in the medial prefrontal cortex (mPFC) is modulated during tasks that assess response inhibition or if these neural correlates, along with behavior, are affected by PNE. To address this issue, we recorded from single mPFC neurons in control and PNE rats as they performed a stop-signal task. We found that PNE rats were faster for all trial-types, made more premature responses, and were less likely to inhibit behavior on 'STOP' trials during which rats had to inhibit an already initiated response. Activity in mPFC was modulated by response direction and was positively correlated with accuracy and movement time in control but not PNE rats. Although the number of single neurons correlated with response direction was significantly reduced by PNE, neural activity observed on general STOP trials was largely unaffected. However, dramatic behavioral deficits on STOP trials immediately following non-conflicting (GO) trials in the PNE group appear to be mediated by the loss of conflict monitoring signals in mPFC. We conclude that prenatal nicotine exposure makes rats impulsive and disrupts firing of mPFC neurons that carry signals related to response direction and conflict monitoring.

Separating Family-Level and Direct Exposure Effects of Smoking During Pregnancy on Offspring Externalizing Symptoms: Bridging the Behavior Genetic and Behavior Teratologic Divide

Maternal smoking during pregnancy (MSDP) has been robustly associated with externalizing problems and their developmental precursors in offspring in studies using behavioral teratologic designs (Wakschlag et al., Am J Public Health 92(6):966-974, 2002; Espy et al., Dev Psychol 47(1):153-169, 2011). In contrast, the use of behavior genetic approaches has shown that the effects commonly attributed to MSDP can be explained by family-level variables (D'Onofrio et al., Dev Psychopathol 20(01):139-164, 2008). Reconciling these conflicting findings requires integration of these study designs. We utilize longitudinal data on a preschool proband and his/her sibling from the Midwest Infant Development Study-Preschool (MIDS-P) to test for teratologic and family level effects of MSDP. We find considerable variation in prenatal smoking patterns both within and across pregnancies within families, indicating that binary smoking measures are not sufficiently capturing exposure. Structural equation models indicate that both conduct disorder and oppositional defiant disorder symptoms showed unique effects of MSDP over and above family level effects. Blending high quality exposure measurement with a within-family design suggests that it is premature to foreclose the possibility of a teratologic effect of MSDP on externalizing problems. Implications and recommendations for future studies are discussed.

Nicotine Exposure During Pregnancy Results in Persistent Midline Epithelial Seam With Improper Palatal Fusion

INTRODUCTION

Nonsyndromic cleft palate is a common birth defect (1:700) with a complex etiology involving both genetic and environmental risk factors. Nicotine, a major teratogen present in tobacco products, was shown to cause alterations and delays in the developing fetus.

METHODS

To demonstrate the postpartum effects of nicotine on palatal development, we delivered three different doses of nicotine (1.5, 3.0, and 4.5mg/kg/d) and sterile saline (control) into pregnant BALB/c mice throughout their entire pregnancy using subcutaneous micro-osmotic pump. Dams were allowed to deliver (~day 21 of pregnancy) and neonatal assessments (weight, length, nicotine levels) were conducted, and palatal tissues were harvested for morphological and molecular analyses, as well as transcriptional profiling using microarrays.

RESULTS

Consistent administration of nicotine caused developmental retardation, still birth, low birth weight, and significant palatal size and shape abnormality and persistent midline epithelial seam in the pups. Through microarray analysis, we detected that 6232 genes were up-regulated and 6310 genes were down-regulated in nicotine-treated groups compared to the control. Moreover, 46% of the cleft palate-causing genes were found to be affected by nicotine exposure. Alterations of a subset of differentially expressed genes were illustrated with hierarchal clustering and a series of formal pathway analyses were performed using the bioinformatics tools.

CONCLUSIONS

We concluded that nicotine exposure during pregnancy interferes with normal growth and development of the fetus, as well results in persistent midline epithelial seam with type B and C patterns of palatal fusion.

IMPLICATIONS

Although there are several studies analyzing the genetic and environmental causes of palatal deformities, this study primarily shows the morphological and large-scale genomic outcomes of gestational nicotine exposure in neonatal mice palate.The previous version was incorrect. New authors Ali Nawshad, Hasan Otu, Janki Sharma, and Elizabeth Sheldon have been included in this version; the funding and acknowledgement sections have been updated accordingly; the article title, some text, and one supplementary data file have been edited; and the corresponding author has been changed. The original corresponding author regrets these earlier errors.

Prenatal nicotine is associated with reduced AMPA and NMDA receptor-mediated rises in calcium within the laterodorsal tegmentum: a pontine nucleus involved in addiction processes

Despite huge efforts from public sectors to educate society as to the deleterious physiological consequences of smoking while pregnant, 12–25% of all babies worldwide are born to mothers who smoked during their pregnancies. Chief among the negative legacies bestowed to the exposed individual is an enhanced proclivity postnatally to addict to drugs of abuse, which suggests that the drug exposure during gestation changed the developing brain in such a way that biased it towards addiction. Glutamate signalling has been shown to be altered by prenatal nicotine exposure (PNE) and glutamate is the major excitatory neurotransmitter within the laterodorsal tegmental nucleus (LDT), which is a brainstem region importantly involved in responding to motivational stimuli and critical in development of drug addiction-associated behaviours, however, it is unknown whether PNE alters glutamate signalling within this nucleus. Accordingly, we used calcium imaging, to evaluate AMPA and NMDA receptor-mediated calcium responses in LDT brain slices from control and PNE mice. We also investigated whether the positive AMPA receptor modulator cyclothiazide (CYZ) had differential actions on calcium in the LDT following PNE. Our data indicated that PNE significantly decreased AMPA receptor-mediated calcium responses, and altered the neuronal calcium response to consecutive NMDA applications within the LDT. Furthermore, CYZ strongly potentiated AMPA-induced responses, however, this action was significantly reduced in the LDT of PNE mice when compared with enhancements in responses in control LDT cells. Immunohistochemical processing confirmed that calcium imaging recordings were obtained from the LDT nucleus as determined by presence of cholinergic neurons. Our results contribute to the body of evidence suggesting that neurobiological changes are induced if gestation is accompanied by nicotine exposure. We conclude that in light of the role played by the LDT in motivated behaviour, the cellular changes in the LDT induced by exposures to nicotine prenatally, when combined with alterations in other reward-related regions, could contribute to the increased susceptibility to smoking observed in the offspring.

IV prenatal nicotine exposure increases the reinforcing efficacy of methamphetamine in adult rat offspring

BACKGROUND

Maternal smoking during pregnancy is correlated with increased substance use in offspring. Research using rodent models shows that gestational nicotine exposure produces enduring alterations in the neurodevelopment of motivational systems, and that rats prenatally treated with nicotine have altered motivation for drug reinforcement on fixed-ratio (FR) schedules of reinforcement.

OBJECTIVE

The present study investigated methamphetamine (METH) self-administration in adult offspring prenatally exposed to intravenous (IV) nicotine or saline using a progressive-ratio (PR) schedule of reinforcement.

METHODS

Pregnant rats were administered IV prenatal saline (PS) or nicotine (PN; 0.05mg/kg/infusion), 3×/day during gestational days 8-21. At postnatal day 70, offspring acquired a lever-press response for sucrose (26%, w/v; FR1-3). Rats were trained with METH (0.05mg/kg/infusion), and following stable FR responding, animals were tested using a progressive-ratio (PR) schedule for three different doses of METH (0.005, 0.025, and 0.05mg/kg/infusion).

RESULTS

METH infusion, active lever presses, and the ratio breakpoint are reported. PN-exposed animals exhibited more METH-maintained responding than PS controls, according to a dose×prenatal treatment interaction (e.g., infusions). PN rats self-administered more METH infusions between the range of 0.025 and 0.05, but not for the 0.005mg/kg/infusion dose.

CONCLUSIONS

IV PN-exposure produced enhanced motivation to self-administer METH. These findings indicate that pregnant women who smoke tobacco may impart neurobiological changes in offspring's motivational systems that render them increasingly vulnerable to drug abuse during adulthood.

Long-term effects of gestational nicotine exposure and food-restriction on gene expression in the striatum of adolescent rats

Gestational exposure to environmental toxins such as nicotine may result in detectable gene expression changes in later life. To investigate the direct toxic effects of prenatal nicotine exposure on later brain development, we have used transcriptomic analysis of striatal samples to identify gene expression differences between adolescent Lister Hooded rats exposed to nicotine in utero and controls. Using an additional group of animals matched for the reduced food intake experienced in the nicotine group, we were also able to assess the impact of imposed food-restriction on gene expression profiles. We found little evidence for a role of gestational nicotine exposure on altered gene expression in the striatum of adolescent offspring at a significance level of p<0.01 and |log2 fold change >0.5|, although we cannot exclude the possibility of nicotine-induced changes in other brain regions, or at other time points. We did, however, find marked gene expression differences in response to imposed food-restriction. Food-restriction resulted in significant group differences for a number of immediate early genes (IEGs) including Fos, Fosb, Fosl2, Arc, Junb, Nr4a1 and Nr4a3. These genes are associated with stress response pathways and therefore may reflect long-term effects of nutritional deprivation on the development of the stress system.

The multiple bottle effect is overridden in male and female rats by simultaneous presentation of two oral nicotine solutions

BACKGROUND

Studies on the oral route of nicotine administration in rodents make important contributions to our understanding of human nicotine use, and alternative approaches to smoking cessation. While environmental availability of oral nicotine contributes to voluntary intake and appears to drive consumption initially, solution concentration may exert more control over intake with continued exposure. Further, it is believed that female rodents consume more nicotine and show greater motivation to obtain it than males.

OBJECTIVES

The purpose of our study was to determine voluntary oral nicotine intake patterns following continuous exposure to relatively high concentrations in male and female rats, employing a multiple bottle approach, and to describe the relationship between oral nicotine consumption and sera cotinine.

METHODS

Using five bottles, adult Sprague-Dawley rats were given continuous access to water and 15 μg/ml nicotine solutions or water and 15 and 30 μg/ml nicotine solutions for 2 weeks; blood serum was analyzed for cotinine.

RESULTS

Rats consistently consumed oral nicotine and female rats ingested more nicotine than males, even at relatively high concentrations. Yet, when both concentrations were presented simultaneously, oral nicotine intake did not exceed that of water, thus overriding an environmental, or multiple-bottle, effect. Cotinine was systemically circulated following first-pass hepatic metabolism of nicotine at early, but not at later stages of nicotine exposure.

CONCLUSIONS

Our findings suggest rats will readily and voluntarily ingest considerably higher doses of nicotine than previously reported resulting in initial systemic cotinine, and trends toward sex differences are mitigated by solution concentration.

Intravenous prenatal nicotine exposure increases orexin expression in the lateral hypothalamus and orexin innervation of the ventral tegmental area in adult male rats

BACKGROUND

Approximately 18% of pregnant women continue to smoke tobacco cigarettes throughout pregnancy. Offspring exposed to tobacco smoke in utero exhibit a higher incidence of drug use in later stages of development relative to non-exposed children. Animal models indicate that prenatal nicotine (PN) exposure alone alters the development of the mesocorticolimbic dopamine (DA) system, which, in part, organizes motivated behavior and reward. The orexin/hypocretin neuropeptide system, which originates in the lateral hypothalamus (LH), projects to key areas of the mesocorticolimbic DA pathway. Previous research suggests that orexin exerts a major influence on motivation and reward.

METHODS

The present experiments determined if intravenous (IV) PN exposure alters (1) the expression of orexin neurons and melanin-concentrating hormone (MCH; positive control) in the LH; and (2) orexin projections from the LH onto DA neurons in the ventral tegmental area (VTA). Dams were injected with IV nicotine (0.05 mg/kg/injection) or saline 3×/day during gestational days 8-21. Tissues from adult male offspring (∼130 days) were examined using immunohistochemistry.

RESULTS

Relative to controls, offspring of IV PN exposure showed (1) increased numbers of orexin neurons in the LH, and no changes in the expression of MCH; and (2) increased orexin appositions on DA cells in the VTA.

CONCLUSION

The findings indicate that the influence of PN exposure is enduring, and suggests that the PN-induced modification of orexin expression on mesolimbic circuitry may contribute to the reported changes in motivated behaviors related to food and drug reward observed in offspring prenatally exposed to nicotine.

Transient suppression of late-stage neuronal progenitor cell differentiation in the hippocampal dentate gyrus of rat offspring after maternal exposure to nicotine

To examine the developmental exposure effect of nicotine (NIC) on hippocampal neurogenesis, pregnant Sprague-Dawley rats were treated with (-)-NIC hydrogen tartrate salt through drinking water at 2, 10 or 50 ppm from gestational day 6 to day 21 after delivery. On postnatal day (PND) 21, immunohistochemically doublecortin (Dcx)(+) cells increased at ≥10 ppm in the dentate subgranular zone (SGZ) as examined in male offspring; however, dihydropyrimidinase-like 3 (TUC4)(+) cells decreased at 2 ppm, and T box brain 2 (Tbr2)(+) cells were unchanged at any dose. Double immunohistochemistry revealed decreases in TUC4(+)/Dcx(+) and TUC4(+)/Dcx(-) cells, an increase in TUC4(-)/Dcx(+) cells at 2 and 10 ppm and an increase in Tbr2(-)/Dcx(+) cells at 50 ppm, suggesting an increase in type-3 progenitor cells at ≥2 ppm and decrease in immature granule cells at 2 and 10 ppm. The number of mature neuron-specific NeuN(-) progenitor cells expressing nicotinic acetylcholine receptor α7 in the SGZ and mRNA levels of Chrna7 and Chrnb2 in the dentate gyrus was unchanged at any dose, suggesting a lack of direct nicotinic stimulation on progenitor cells. In the dentate hilus, glutamic acid decarboxylase 67(+) interneurons increased at ≥10 ppm. All changes disappeared on PND 77. Therefore, maternal exposure to NIC reversibly affects hippocampal neurogenesis targeting late-stage differentiation in rat offspring. An increase in interneurons suggested that their activation affected granule cell differentiation. The lowest observed adverse effect level was at 2 ppm (0.091 mg/kg/day as a free base) by the affection of hippocampal neurogenesis at ≥2 ppm.

Hyperactivity, increased nicotine consumption and impaired performance in the five-choice serial reaction time task in adolescent rats prenatally exposed to nicotine

RATIONALE

Prenatal exposure to nicotine has been linked to accelerated risk for different psychiatric disorders, including conduct disorder, attention deficit hyperactivity disorder (ADHD) and drug abuse. We examine a potential link between prenatal nicotine exposure, hyperactivity, anxiety, nicotine consumption, and cognitive performance in rats.

METHODS

Adolescent offspring of females exposed during pregnancy to 0.06 mg/ml nicotine solution as the only source of water and of a group of pair-fed females, used as a control for anorexic effects of nicotine, were evaluated in a battery of tests, including locomotor activity, the elevated plus maze, two-bottle free-choice nicotine solution consumption, the five-choice serial reaction time test (5-CSRTT) and a delay-discounting test. All tests were conducted between postnatal day (PND) 25 and PND 50.

RESULTS

Nicotine-exposed animals expressed hyperactivity, increased number of open arms entries in the elevated plus maze and increased numbers of anticipatory responses in the 5-CSRTT. Decreased aversion for nicotine solution in the free-choice test and decreased numbers of omission errors in the 5-CSRTT were observed both in nicotine-exposed and pair-fed offspring. Neither nicotine exposure nor pair-feeding had an effect on impulsive choice in a delay-discounting test.

CONCLUSIONS

Our study confirms deleterious effects of prenatal nicotine exposure on important aspects of behaviour and inhibitory control in adolescent rats and supports epidemiological findings that show increased levels of symptoms of ADHD and related disorders among those whose mothers smoked during their pregnancy. It also suggests a link between food restriction during pregnancy and addiction-related behaviours in offspring.

Offspring of Prenatal IV Nicotine Exposure Exhibit Increased Sensitivity to the Reinforcing Effects of Methamphetamine

Maternal smoking during pregnancy is associated with increased substance abuse in offspring. Preclinical research shows that in utero exposure to nicotine, the primary psychoactive compound in tobacco smoke, influences the neurodevelopment of reward systems and alters motivated behavior in offspring. The present study determined if prenatal nicotine (PN) exposure altered the sensitivity to the reinforcing and aversive effects of methamphetamine (METH) in offspring using a low dose, intravenous (IV) exposure method. Pregnant dams were administered nicotine (0.05 mg/kg/injection) or prenatal saline (PS) 3×/day on gestational days 8–21, and adult offspring were tested using METH self-administration (experiment 1) or METH-induced conditioned taste aversion (CTA; experiment 2) procedures. For METH self-administration, animals were trained to respond for IV METH (0.05 mg/kg/infusion; fixed-ratio 3) and they were tested on varying doses of the reinforcer (0.0005–1.0 mg/kg/infusion). For METH CTA, rats received three saccharin and METH pairings (0, 0.3, or 0.5 mg/kg, sc) followed by 14 daily extinction trials. Experiment 1: PN and PS animals exhibited inverted U-shaped dose-response curves; however, the PN animal’s curve was shifted to the left, suggesting PN animals were more sensitive to the reinforcing effects of METH. Experiment 2: METH CTA was acquired in a dose-dependent manner and the factor of PN exposure was not related to the acquisition or extinction of METH-induced CTA. There were no sex differences in either experiment. These results indicate that IV PN-exposed adult offspring exhibited increased sensitivity to IV METH. This suggests that PN exposure, via maternal smoking, will alter the reinforcing effects of METH during later stages of development, and furthermore, will influence substance use vulnerability in adult human offspring.

Nicotine occurrence in bottled mineral water: analysis of 10 brands of water in Spain

The presence of pharmaceuticals in surface and drinking water has been evidenced in numerous studies. Despite representing one of the most common consumption sources, to the best of our knowledge, this is the first report on the presence of pharmaceutical compounds in bottled mineral water. Pollution of these sources not only could pose a serious human health risk, but would also warn about the quality of the water in our aquifers, a vital and vulnerable source of water, essential for the future water supply. Fifty eight pharmaceutically active compounds (PhACs) belonging to the 12 main therapeutic groups were analyzed in 10 bottled mineral water brands produced in Spain. Nicotine was detected in concentrations ranging from 7ngL(-1) to 15ngL(-1) in 5 of 10 bottled mineral waters. Despite the low nicotine concentration measured, the presence of this compound in bottled water still raises concern. Health risk assessment researchers have postulated that the risk to adult healthy humans from oral intake of nicotine at low levels is negligible. However, no studies have been conducted to assess the human health risk of vulnerable populations such as pregnant women and newborns. This population is the target of advertising on the purity and quality characteristics of bottled mineral water.

GSTM1 modifies the effect of maternal exposure to environmental tobacco smoke on neonatal primitive reflexes

OBJECTIVE

The aim of this study was to examine whether infant metabolic gene polymorphisms modify the effect of maternal environmental tobacco smoke (ETS) on neonatal neurobehavior.

METHODS

We conducted a birth cohort study of 87 nonsmoking women who delivered single births of normal birth weight. We enrolled the women before delivery, interviewed them using a structured questionnaire, and collected umbilical cord blood. Umbilical cord cotinine, a blood indicator of prenatal ETS exposure, was analyzed. The Neonatal Neurobehavioral Examination-Chinese Version (NNE-C) was administrated within 5 days after delivery to examine neonatal neurobehavior. Four infant metabolic genes, CYP1A1 MspI, CYP1A1 Ile462Val, GSTT1, and GSTM1, were identified.

RESULTS

Maternal ETS exposure during pregnancy was not related to neonatal neurobehavior when infant genetic polymorphisms were not considered. However, maternal ETS exposure did cause adverse effects in neonates with the absent type of GSTM1. Adverse effects were seen on the total NNE-C (β = -2.55; p = .02) and on primitive reflexes (β = -1.70; p = .004), especially in grasp reflexes (β = -.36; p = .011) and tonic neck reflexes (β = -.36; p = .049). In addition, there was a significant interaction between maternal ETS exposure and infant GSTM1 genotype on neonate grasp reflexes (p for interaction = .019).

CONCLUSIONS

These data indicate that weaker responses in neonatal primitive reflexes in infants with the absent type GSTM1 were related to maternal ETS exposure during pregnancy.

Prenatal exposure to nicotine impairs performance of the 5-choice serial reaction time task in adult rats

Cigarette smoking is associated with a wide variety of adverse reproductive outcomes, including increased infant mortality and decreased birth weight. Prenatal exposure to tobacco smoke, of which nicotine is a major teratogenic component, has also been linked to the acceleration of the risk for different psychiatric disorders, including conduct disorder and attention deficit hyperactivity disorder (ADHD). Whether this increased risk is influenced by the direct effects of gestational nicotine exposure on the developing fetus remains uncertain. In this study we provide experimental evidence for the effects of prenatal nicotine exposure on measures of attention and impulsivity in adult male rats. Offspring of females exposed during pregnancy to 0.06 mg/ml nicotine solution as the only source of water (daily consumption: 69.6±1.4 ml/kg; nicotine blood level: 96.0±31.9 ng/ml) had lower birth weight and delayed sensorimotor development measured by negative geotaxis, righting reflex, and grip strength. In the 5-choice serial reaction time test, adult rats showed increased numbers of anticipatory responses and omissions errors, more variable response times, and lower accuracy with evidence of delayed learning of the task demands when the 1 s stimulus duration was introduced. In contrast, prenatal nicotine exposure had no effect on exploratory locomotion or delay-discounting test. Prenatal nicotine exposure increased expression of the D5 dopamine receptor gene in the striatum, but did not change expression of other dopamine-related genes (DRD4, DAT1, NR4A2, and TH) in either the striatum or the prefrontal cortex. These data suggest a direct effect of prenatal nicotine exposure on important aspects of attention, inhibitory control, or learning later in life.