Child development after maternal tocolysis with beta-sympathomimetic drugs

Norepinephrine, neurodevelopment and behavior

Neurotransmitters play critical roles in the developing nervous system. Among the neurotransmitters, norepinephrine (NE) is in particular postulated to be an important regulator of brain development. NE is expressed during early stages of development and is known to regulate both the development of noradrenergic neurons and the development of target areas. NE participates in the shaping and the wiring of the nervous system during the critical periods of development, and perturbations in this process can alter the brain's developmental trajectory, which in turn can cause long-lasting and even permanent changes in the brain function and behavior later in life. Here we will briefly review evidence for the role of noradrenergic system in neurodevelopmental processes and will discuss about the potential disruptors of noradrenergic system during development and their behavioral consequences.

Parental asthma and risk of autism spectrum disorder in offspring: A population and family-based case-control study

BACKGROUND

Associations between parental asthma and prenatal exposure to asthma medications with offspring autism spectrum disorder (ASD) have been reported. However, the associations might be confounded by unmeasured (genetic and shared environmental) familial factors.

OBJECTIVE

We investigated the association between (a) maternal/paternal asthma and offspring ASD, and (b) prenatal exposures to β2-agonists, other asthma medications and offspring ASD using cases and controls selected from the population as well as biological relatives with different degrees of relatedness.

METHODS

We included all children (N = 1 579 263) born in Sweden 1992-2007. A nested case-control design was used to compare 22 894 ASD cases identified from the National Patient Register to (a) 228 940 age-, county- and sex-matched controls randomly selected from the population, (b) their eligible full-siblings (n = 1267), (c) half-siblings (n = 1323), (d) full-cousins (n = 11 477) and (e) half-cousins (n = 3337). Conditional logistic regression was used to estimate the odds ratios (OR) and 95% confidence intervals (CI) for ASD in children differentially exposed to parental asthma or prenatal asthma medications.

RESULTS

Maternal asthma was associated with increased risk of offspring ASD (OR 1.43, 95% CI 1.38-1.49); there was a weaker association for paternal asthma (OR 1.17, 95% CI 1.11-1.23). The risk of offspring ASD in mothers with asthma showed similar estimates when adjusting for shared familial factors among paternal half-siblings (OR 1.20, 95% CI 0.80-1.81), full-cousins (OR 1.28, 95% CI 1.16-1.41) and half-cousins (OR 1.30, 95% CI 1.10-1.54), albeit with wider confidence intervals. Prenatal exposure to asthma medications among subjects whose mothers had asthma was not associated with subsequent ASD.

CONCLUSIONS AND CLINICAL RELEVANCE

In this large observational study, parental asthma was associated with slightly elevated risk of ASD in offspring. More specifically, the increased risk by maternal asthma did not seem to be confounded by familial factors. There was no evidence of an association between asthma medications during pregnancy and offspring ASD.

Clinical Practice Guideline for the Management of Infantile Hemangiomas

Infantile hemangiomas (IHs) occur in as many as 5% of infants, making them the most common benign tumor of infancy. Most IHs are small, innocuous, self-resolving, and require no treatment. However, because of their size or location, a significant minority of IHs are potentially problematic. These include IHs that may cause permanent scarring and disfigurement (eg, facial IHs), hepatic or airway IHs, and IHs with the potential for functional impairment (eg, periorbital IHs), ulceration (that may cause pain or scarring), and associated underlying abnormalities (eg, intracranial and aortic arch vascular abnormalities accompanying a large facial IH). This clinical practice guideline for the management of IHs emphasizes several key concepts. It defines those IHs that are potentially higher risk and should prompt concern, and emphasizes increased vigilance, consideration of active treatment and, when appropriate, specialty consultation. It discusses the specific growth characteristics of IHs, that is, that the most rapid and significant growth occurs between 1 and 3 months of age and that growth is completed by 5 months of age in most cases. Because many IHs leave behind permanent skin changes, there is a window of opportunity to treat higher-risk IHs and optimize outcomes. Early intervention and/or referral (ideally by 1 month of age) is recommended for infants who have potentially problematic IHs. When systemic treatment is indicated, propranolol is the drug of choice at a dose of 2 to 3 mg/kg per day. Treatment typically is continued for at least 6 months and often is maintained until 12 months of age (occasionally longer). Topical timolol may be used to treat select small, thin, superficial IHs. Surgery and/or laser treatment are most useful for the treatment of residual skin changes after involution and, less commonly, may be considered earlier to treat some IHs.

Cardiotoxicity of β-mimetic catecholamines during ontogenetic development - possible risks of antenatal therapy

Catecholamines are involved in the regulation of a wide variety of vital functions. The β-adrenergic receptor (β-AR) - adenylyl cyclase system has been identified early in embryogenesis before the heart has received adrenergic innervation. The structure of β-receptors in the immature myocardium is similar to that in adults; there are, however, significant quantitative developmental changes in the inotropic and chronotropic responsiveness. Information on the toxic effect of the β-AR agonists in the immature heart is surprisingly scarce, even though these agents are used in clinical practice both during pregnancy and in early postnatal development. Large doses of β-AR agonists induce malformations of the cardiovascular system; the type of change depends upon the time at which the β-AR agonist was administered during embryogenesis. During postnatal ontogeny, the cardiotoxicity of β-AR agonists increased from birth to adulthood. It seems likely that despite interspecies differences, developmental changes in the cardiac sensitivity to β-AR agonists may exist in all mammals, depending on the degree of maturation of the system involved in β-adrenergic signaling. All the existing data draw attention to the possible harmful consequences of the clinical use of β-AR agonists during early phases of cardiac development. Late effects of the early disturbances of the cardiac muscle cannot be excluded.

Risk of childhood cerebral palsy following prenatal exposure to ß2-adrenergic receptor agonist: A nationwide cohort study

Background

Cerebral palsy (CP) is the most common physical developmental disability in childhood with a prevalence of 2 to 3 per 1000 live births. β2-adrenoreceptor agonist (β2AA) are widely used for the treatment of asthma. Maternal use of β2AAs may increase the risk of adverse neuro-psychiatric health outcomes in the offspring. No study, however, has evaluated the effect of prenatal exposure to β2AAs on the risk of CP.

Objective

To examine the association between prenatal exposure to β2AAs and the risk of childhood cerebral palsy.

Methods

This population-based cohort study included all live singleton births in Denmark from January 1, 1997 to December 31, 2003. The information on outpatient prescriptions of β2AAs was extracted from Danish National Prescription Registry. Children born to mothers who used β2AAs from 30 days before pregnancy until delivery were categorized as the exposed. To differentiate the effect of β2AAs from the underlying indications, the exposure window was further extended to 2 years before pregnancy and the exposed groups were re-defined to represent different periods of exposure to maternal use of β2AAs (use only before pregnancy, use only during pregnancy, and use both before and during pregnancy). Cases of CP were identified from the Danish Cerebral Palsy Register. Logistic regression was used to estimate incidence odds ratio (OR) of CP.

Results

Among all the 442,278 singletons, 19,616 (4.44%) were exposed to β2AAs in utero (from 30 days before pregnancy until delivery). The risk of childhood CP was 0.21% in exposed and 0.19% in unexposed group, yielding an adjusted OR (aOR) 1.12 (95% confidence interval (CI): 0.82, 1.53). When extending the exposure time window to 2 years prior to pregnancy, no overall significant association was observed regardless of the exposure period. However, an increased risk of CP (aOR = 1.41, 95%CI: 0.92, 2.18) for maternal β2AAs use during pregnancy was observed in female offspring, especially in those born at term (aOR = 1.65, 95%CI: 1.02, 2.67). This increase was mainly attributed to an increased risk in those born to mothers who used β2AAs both before and during pregnancy (aOR = 1.81, 95%CI: 0.99, 3.33).

Conclusions

We observed an association between maternal β2AAs use during pregnancy and an increased risk of CP in female offspring, but we could not rule out confounding by the underlying indications for β2AAs.

Early life exposure to air pollution particulate matter (PM) as risk factor for attention deficit/hyperactivity disorder (ADHD): Need for novel strategies for mechanisms and causalities

Epidemiological studies have demonstrated that air pollution particulate matter (PM) and adsorbed toxicants (organic compounds and trace metals) may affect child development already in utero. Recent studies have also indicated that PM may be a risk factor for neurodevelopmental disorders (NDDs). A pattern of increasing prevalence of attention deficit/hyperactivity disorder (ADHD) has been suggested to partly be linked to environmental pollutants exposure, including PM. Epidemiological studies suggest associations between pre- or postnatal exposure to air pollution components and ADHD symptoms. However, many studies are cross-sectional without possibility to reveal causality. Cohort studies are often small with poor exposure characterization, and confounded by traffic noise and socioeconomic factors, possibly overestimating the study associations. Furthermore, the mechanistic knowledge how exposure to PM during early brain development may contribute to increased risk of ADHD symptoms or cognitive deficits is limited. The closure of this knowledge gap requires the combined use of well-designed longitudinal cohort studies, supported by mechanistic in vitro studies. As ADHD has profound consequences for the children affected and their families, the identification of preventable risk factors such as air pollution exposure should be of high priority.

Developmental neurotoxicity resulting from pharmacotherapy of preterm labor, modeled in vitro: Terbutaline and dexamethasone, separately and together

Terbutaline and dexamethasone are used in the management of preterm labor, often for durations of treatment exceeding those recommended, and both have been implicated in increased risk of neurodevelopmental disorders. We used a variety of cell models to establish the critical stages at which neurodifferentiation is vulnerable to these agents and to determine whether combined exposures produce a worsened outcome. Terbutaline selectively promoted the initial emergence of glia from embryonic neural stem cells (NSCs). The target for terbutaline shifted with developmental stage: at later developmental stages modeled with C6 and PC12 cells, terbutaline had little effect on glial differentiation (C6 cells) but impaired the differentiation of neuronotypic PC12 cells into neurotransmitter phenotypes. In contrast to the specificity shown by terbutaline, dexamethasone affected both neuronal and glial differentiation at all stages, impairing the emergence of both cell types in NSCs but with a much greater impairment for glia. At later stages, dexamethasone promoted glial cell differentiation (C6 cells), while shifting neuronal cell differentiation so as to distort the balance of neurotransmitter phenotypes (PC12 cells). Finally, terbutaline and dexamethasone interacted synergistically at the level of late stage glial cell differentiation, with dexamethasone boosting the ability of terbutaline to enhance indices of glial cell growth and neurite formation while producing further decrements in glial cell numbers. Our results support the conclusion that terbutaline and dexamethasone are directly-acting neuroteratogens, and further indicate the potential for their combined use in preterm labor to worsen neurodevelopmental outcomes.

Association between Beta-Sympathomimetic Tocolysis and Risk of Autistic Spectrum Disorders, Behavioural and Developmental Outcome in Toddlers

AIM

To investigate whether maternal intravenous beta-mimetic tocolytic therapy increases the risk of autistic spectrum disorders (ASD) and poorer behavioural and developmental outcomes.

METHOD

Our study is a prospective case-control study among 90 children between 1.5 and three years old. Cases (n = 46) were toddlers with betamimetic tocolytic exposure; control group toddlers (n = 44) were tocolytic untreated. Treated and untreated groups were also divided into subgroups: term and preterm delivered. The gestational age of tocolytic treatment start, the dose and duration of exposure in hours were obtained from obstetric medical records. The Brief Infant-Toddler Social and Emotional Assessment (BITSEA), the Modified Checklist for Autism in Toddlers (M-CHAT) and the Denver Developmental Screening Test (DDST) tests were applied for evaluation of social, emotional problems, autism and developmental disorders.

RESULTS

Term and preterm born toddlers treated tocolytically in utero didn't demonstrate a higher risk of autistic disorders or poorer behavioural and developmental results than controls. In the preterm group, the earliest start of tocolytic treatment was correlated with toddlers lower score of the Competencies Scale (p = 0.009) and a higher score of the Problems Scale (p = 0.048). Also, we concluded that preterm membrane rupture was associated with higher ASD risk in the untreated group (p = 0.043).

CONCLUSION

Exposure to betamimetics during pregnancy was not associated with an increased risk of autism, behavioural and developmental disorders.

In utero exposure to β-2-adrenergic receptor agonist and attention-deficit/hyperactivity disorder in children

We aimed to examine the association between in utero exposure to β2AA and risk of attention-deficit/hyperactivity disorder (ADHD). We established a cohort of 672,265 children born from 1998 to 2008 in Denmark. Children were categorized as exposed if their mothers had redeemed a prescription of β2AA in pregnancy (from 30 days prior to conception until delivery). We identified children diagnosed with ADHD in the Danish National Hospital Register for the first time after his/her third birthday. Log-linear Poisson regression was used to estimate adjusted incidence rate ratio (aIRR) of ADHD. In total, 25,434 children were born to mothers who had redeemed a β2AA prescription in pregnancy. The exposed children had a 1.31-fold increased risk [aIRR = 1.30, 95% confidence interval (CI):1.20-1.42] of ADHD compared to unexposed children after adjusting for potential confounders. However, when extending the exposure window to 2 years prior to conception until delivery, exposure to maternal use of β2AA only before pregnancy, only during pregnancy, and both before and during pregnancy was associated with elevated risks of ADHD in children, with aIRRs of 1.31 (95% CI 1.22-1.40), 1.38 (95% CI 1.22-1.57), and 1.30 (95% CI 1.16-1.45), respectively. In mothers with a history of asthma, no association was observed between maternal use of β2AA during pregnancy and ADHD in offspring (aIRR = 0.92, 95% CI 0.74-1.15). In utero exposure to β2AA was associated with an increased risk of ADHD in children. However, it is more likely that confounding by indication, the underlying disorders or associated pathological conditions, may explain the association.

Benzo(a)pyrene triggers desensitization of β2-adrenergic pathway

Exposure to environmental polycyclic aromatic hydrocarbons (PAHs), such as benzo(a)pyrene (B(a)P), has been linked to several health-threatening risks. PAHs were also shown to hinder adrenergic receptor (ADR) responses. As we previously demonstrated that B(a)P can directly interact with the β2ADR, we investigated here whether B(a)P could decrease β2ADR responsiveness by triggering receptor desensitization phenomena. We firstly showed that exposure to B(a)P reduced β2ADR-mediated epinephrine-induced induction of NR4A gene mRNAs and of intracellular cAMP. Analysis of β2ADR protein expression demonstrated that B(a)P rapidly decreased membrane expression of β2ADR with a subsequent degradation of receptor protein. B(a)P exposure concomitantly rapidly increased the β2ADR mRNA levels. The use of the β-blockers, propranolol and ICI 118.551, demonstrated the involvement of β2ADR itself in this increase. However, sustained exposure to B(a)P induced a diminution of β2ADR mRNA steady-state as a result of the acceleration of its degradation. Together, these results show that, beside the well-known activation of the aryl hydrocarbon receptor, PAH deleterious effects may involve the dysfunction of adrenergic responses through, in part, the desensitization of β2ADR. This may be taken in consideration when β2-agonists/antagonists are administered in patients exposed to important concentrations of PAHs, e.g. in cigarette smokers.

Terbutaline and Associated Risks for Neurodevelopmental Disorders

Preterm labor often leads to a preterm birth and has been shown to be the most important determinant of risk for perinatal morbidity and mortality. While medication management has been utilized by physicians to delay preterm labor, the results these medications achieve remain inconsistent, in addition to increasing the risk to the developing fetus. Terbutaline has been among the most commonly used β2-adrenoreceptor (β2AR) agonists in the management of preterm labor. The research suggests that tocolytic terbutaline therapy carries a significant risk for the mother and the child, which can be magnified by extended exposure, sex of the fetus, and administration during critical fetal developmental periods. This paper highlights the research on terbutaline in treatment of preterm labor, along with the possible associated cognitive deficits in adolescents who were treated with terbutaline in utero. Two case summaries are presented to illustrate the potential deficits in clinical presentations of adolescents with history of intrauterine exposure to terbutaline. Publicizing the association between terbutaline and these deficits can not only assist obstetricians and expectant mothers in making a more informed choice in the treatment of preterm labor but also provide neuropsychologists and pediatricians with information helpful in understanding the etiology of these impairments.

Terbutaline impairs the development of peripheral noradrenergic projections: potential implications for autism spectrum disorders and pharmacotherapy of preterm labor

Terbutaline, a β2-adrenoceptor agonist, is used off-label for long-term management of preterm labor; such use is associated with increased risk of neurodevelopmental disorders, including autism spectrum disorders. We explored the mechanisms underlying terbutaline's effects on development of peripheral sympathetic projections in developing rats. Terbutaline administration on postnatal days 2-5 led to immediate and persistent deficiencies in cardiac norepinephrine levels, with greater effects in males than in females. The liver showed a lesser effect; we reasoned that the tissue differences could represent participation of retrograde trophic signaling from the postsynaptic site to the developing neuronal projection, since hepatic β2-adrenoceptors decline in the perinatal period. Accordingly, when we gave terbutaline earlier, on gestational days 17-20, we saw the same deficiencies in hepatic norepinephrine that had been seen in the heart with the later administration paradigm. Administration of isoproterenol, which stimulates both β1- and β2-subtypes, also had trophic effects that differed in direction and critical period from those elicited by terbutaline; methoxamine, which stimulates α1-adrenoceptors, was without effect. Thus, terbutaline, operating through trophic interactions with β2-adrenoceptors, impairs development of noradrenergic projections in a manner similar to that previously reported for its effects on the same neurotransmitter systems in the immature cerebellum. Our results point to the likelihood of autonomic dysfunction in individuals exposed prenatally to terbutaline; in light of the connection between terbutaline and autism, these results could also contribute to autonomic dysregulation seen in children with this disorder.

Absence of neurotoxicity with medicinal grade terbutaline in the rat model

To evaluate neurological effects of terbutaline, rats were injected with saline, terbutaline (Sigma or American Pharmaceutical Partners (APP™)) at 0.5 mg/kg-d or 10 mg/kg-d between postnatal days (PND) 2-5 or 11-14. Brains collected 24 h after last injection were used to determine corpus-callosum thickness, Purkinje cell and neuronal number in the cerebellum. Ambulation, distance traveled, resting time and time on rotarod were analyzed. Terbutaline (both doses/grades at PND 11-14) decreased corpus-callosum thickness. Ambulation time was significantly decreased in the 10 mg/kg-d (Sigma) and 0.5 mg/kg-d of terbutaline (APP™) (PND 2-5) juvenile-rats and 10 mg/kg-d-Sigma adult-rats, 0.5 mg/kg-d APP™ (PND 11-14) adult-rats. Resting time was increased in both doses of APP™ (PND 2-5) in juvenile-rats, 10 mg/kg-d Sigma adult-rats. 10 mg/kg-d-Sigma (PND 2-5) decreased distance traveled in adult-rats. 0.5 mg/kg-d-Sigma (PND 2-5 and PND 11-14) decreased the time spent on rotarod (30 RPM) in adult-rats. Sigma terbutaline Sigma had 2× as much free base compared to APP™. In conclusion, APP™ terbutaline did not have a deleterious effect on the developing rat brain.

Metabolic activity in the brain of juvenile and adult rats with a neonatal ventral hippocampal lesion

Longitudinal studies on patients for schizophrenia suggest that functional brain perturbations precede the onset of symptoms. Rats with a neonatal ventral hippocampal lesion (NVHL) are considered as a heuristic neurodevelopmental model of schizophrenia. We characterized basal metabolic changes observed in NVHL rats before and after the age when known behavioral alterations have been reported. Male pups were lesioned with ibotenic acid at postnatal day 7 (PD7). We measured local cerebral metabolic rates for glucose (LCMRglc) by the quantitative autoradiographic [(14)C]2-deoxyglucose technique at pre- (PD21) and postpubertal (PD42) ages when NVHL rats do not express abnormal dopamine related behaviors, and at adulthood (PD70). We observed a widespread increase in LCMRglcs in PD21 NVHL indicative of an ongoing intense reorganization of the brain while at PD42, increases were less extended. At PD70, changes in glucose metabolism were restricted to specific systems, such as the auditory system, the cerebellum, the serotonergic median raphe, and median septum. These data show in a heuristic animal model of schizophrenia that functional metabolic changes within the brain could precede the onset of dopamine-related behavioral alterations and lead to a distinct ensemble of functional changes in adulthood in systems that may be relevant to schizophrenia.

Neonatal exposure to fenoterol and betamethasone: effects on the behavioral development in the rat

We investigated longitudinally the behavioral development in the rat following exposure to beta-agonists and glucocorticoids (GC). Neonatal rats received either 1 mg/kg fenoterol (FEN), 0.3 mg/kg betamethasone (BET), or saline (SAL). Weanling and young adult rats were tested in the open field, the elevated-plus maze, and the water maze. FEN-treated as well as BET-treated animals displayed increased anxiety-like behavior. Furthermore, BET-treated adult animals showed a reduced locomotor activity. An enhanced 24-h memory in the water maze in both treatment groups may be facilitated by emotional arousal due to the increased anxiety levels. The possible neurobiological underpinnings are discussed in detail.

In utero beta 2 adrenergic agonist exposure and adverse neurophysiologic and behavioral outcomes

Beta 2 adrenergic receptor overstimulation during critical periods of prenatal development can induce a permanent shift in the balance of sympathetic-to-parasympathetic tone. This is a biologically plausible mechanism whereby beta 2 adrenergic agonists can induce functional and behavioral teratogenesis, which explains their association with increases in autism spectrum disorders, psychiatric disorders, poor cognitive, motor function and school performance, and changes in blood pressure in the offspring. The use of beta 2 adrenergic agonists should be limited to proven indications when alternate drugs are ineffective or unavailable; the risks of untreated disease to the mother and fetus are greater than the risk of the beta 2 adrenergic agonist.

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

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

Pleiotropic effects of neurotransmission during development: modulators of modularity

The formation and function of the mammalian cerebral cortex relies on the complex interplay of a variety of genetic and environmental factors through protracted periods of gestational and postnatal development. Biogenic amine systems are important neuromodulators, both in the adult nervous system, and during critical epochs of brain development. Abnormalities in developmental programming likely contribute to developmental delays and multiple neurological and psychiatric disorders, often with symptom onset much later than the actual induction of pathology. We review several genetic and pharmacological models of dopamine, norepinephrine and serotonin modulation during development, each of which produces permanent changes in cerebral cortical structure and function. These models clearly illustrate the ability of these neurotransmitters to function beyond their classic roles and show their involvement in the development and modulation of fine brain circuitry that is sensitive to numerous effectors. Furthermore, these studies demonstrate the need to consider not only gene by environment interactions, but also gene by environment by developmental time interactions.

Fetal mechanisms in neurodevelopmental disorders

Normal development of the central nervous system depends on complex, dynamic mechanisms with multiple spatial and temporal components during gestation. Neurodevelopmental disorders may originate during fetal life from genetic as well as intrauterine and extrauterine factors that affect the fetal-maternal environment. Fetal neurodevelopment depends on cell programs, developmental trajectories, synaptic plasticity, and oligodendrocyte maturation, which are variously modifiable by factors such as stress and endocrine disruption, exposure to pesticides such as chlorpyrifos and to drugs such as terbutaline, maternal teratogenic alleles, and premature birth. Current research illustrates how altered fetal mechanisms may affect long-term physiological and behavioral functions of the central nervous system more significantly than they affect its form, and these effects may be transgenerational. This research emphasizes the diversity of such prenatal mechanisms and the need to expand our understanding of how, when altered, they may lead to disordered development, the signs of which may not appear until long after birth.

Developmental exposure to terbutaline and chlorpyrifos, separately or sequentially, elicits presynaptic serotonergic hyperactivity in juvenile and adolescent rats

Developmental exposure to unrelated neurotoxicants can nevertheless converge on common final targets so as to exacerbate damage or functional deficits. We examined the effects of developmental exposure to terbutaline, a beta2-adrenergic receptor agonist used to arrest preterm labor, and chlorpyrifos, a widely used organophosphate pesticide, on serotonin (5HT) systems. Treatments were chosen to parallel periods typical of human developmental exposures, terbutaline (10 mg/kg) on postnatal days (PN) 2-5 and chlorpyrifos (5 mg/kg) on PN11-14, with assessments conducted in juvenile and adolescent stages (PN21, PN30 and PN45), comparing each agent alone as well as sequential administration of both. By itself, terbutaline produced persistent 5HT presynaptic hyperactivity as evidenced by increased 5HT turnover in brain regions containing 5HT terminal zones; this effect was similar to that seen in earlier studies with chlorpyrifos administration during the same early postnatal period. Later administration of chlorpyrifos (PN11-14) produced a transient increase in 5HT turnover during the juvenile stage, and the sequential exposure paradigm, terbutaline followed by chlorpyrifos, showed a corresponding increase in effect over either agent alone. In combination with our earlier work on 5HT receptors, these results indicate that terbutaline is a developmental neurotoxicant that targets the 5HT system, findings that lend a mechanistic underpinning to clinical indications of elevated childhood psychiatric disorders in the offspring of women treated with beta-agonist tocolytics. Equally importantly, the interaction between terbutaline and chlorpyrifos suggests that tocolytic therapy may alter the subsequent susceptibility to common environmental toxicants.

Neuroinflammation and behavioral abnormalities after neonatal terbutaline treatment in rats: implications for autism

Autism is a neurodevelopmental disorder presenting before 3 years of age with deficits in communication and social skills and repetitive behaviors. In addition to genetic influences, recent studies suggest that prenatal drug or chemical exposures are risk factors for autism. Terbutaline, a beta2-adrenoceptor agonist used to arrest preterm labor, has been associated with increased concordance for autism in dizygotic twins. We studied the effects of terbutaline on microglial activation in different brain regions and behavioral outcomes in developing rats. Newborn rats were given terbutaline (10 mg/kg) daily on postnatal days (PN) 2 to 5 or PN 11 to 14 and examined 24 h after the last dose and at PN 30. Immunohistochemical studies showed that administration of terbutaline on PN 2 to 5 produced a robust increase in microglial activation on PN 30 in the cerebral cortex, as well as in cerebellar and cerebrocortical white matter. None of these effects occurred in animals given terbutaline on PN 11 to 14. In behavioral tests, animals treated with terbutaline on PN 2 to 5 showed consistent patterns of hyper-reactivity to novelty and aversive stimuli when assessed in a novel open field, as well as in the acoustic startle response test. Our findings indicate that beta2-adrenoceptor overstimulation during an early critical period results in microglial activation associated with innate neuroinflammatory pathways and behavioral abnormalities, similar to those described in autism. This study provides a useful animal model for understanding the neuropathological processes underlying autism spectrum disorders.

beta2-Adrenergic receptor gene variants and risk for autism in the AGRE cohort

The beta2-adrenergic receptor is part of the catecholamine system, and variants at two polymorphic sites in the gene coding for the receptor (ADRB2) confer increased activity. Overstimulation of this receptor may alter brain development, and has been linked to autism in non-identical twins. The objective of this study was to determine whether alleles in ADRB2 are associated with diagnosis of autism in the Autism Genetic Resource Exchange (AGRE) population. Three hundred and thirty-one independent autism case-parent trios were included in the analysis. Subjects were genotyped at activity-related polymorphisms rs1042713 (codon 16) and rs1042714 (codon 27). Association between autism and genotypes at each polymorphic site was tested using genotype-based transmission disequilibrium tests, and effect modification by family and pregnancy characteristics was evaluated. Sensitivity to designation of the proband in each family was assessed by performing 1000 repeats of the analysis selecting affected children randomly. A statistically significant OR of 1.66 for the Glu27 homozygous genotype was observed. Increased associations with this genotype were observed among a subset of Autism Diagnostic Observation Schedule confirmed cases and a subset reporting experience of pregnancy-related stressors. In conclusion, the Glu27 allele of the ADRB2 gene may confer increased risk of autism and shows increased strength with exposure to pregnancy related stress.

Use of tocolytics: what is the benefit of gaining even more time?

Today's dogma states that tocolytics can be used to prolong pregnancy for just 48 hours, allowing corticosteroids to be administered and transportation of the mother to a tertiary care centre. Surveys have shown that up to 30% of practitioners use maintenance tocolysis. Theoretically, maintenance tocolysis should be able to improve neonatal outcome by avoiding preterm birth and allowing delivery in the community maternity hospital or even at home, minimising social difficulties created by long distances between the mother and/or her baby and the rest of the family. This should result in fewer neonatal intensive care unit admissions, less respiratory distress syndrome and fewer long-term neurological sequelae. Such an effect has never been proven, probably because we do not know which women benefit from treatment, which do not require treatment because they are not in labour and which babies would better be born because chorioamnionitis and other insults jeopardize intrauterine development. Most studies on long-term tocolysis have been performed with beta-agonists. No improvement has been shown. On the contrary, a trend towards fetal harm with an increased risk for periventricular leucomalacia exists. Results from studies of one tocolytic should not be generalised; one published study on maintenance therapy with atosiban showed prolonged uterine quiescence and prolonged gestation, but was too small to detect differences in neonatal outcome. In the future, we need larger studies, not only to detect whether long-term tocolysis with newer tocolytics (oral oxytocin antagonists, prostaglandin receptor blockers) results in better neonatal outcome, especially at the lower gestational ages but also to discover methods that allow us to identify those women who will benefit from treatment and those for whom prolongation of pregnancy may cause harm.

Imbalances emerge in cardiac autonomic cell signaling after neonatal exposure to terbutaline or chlorpyrifos, alone or in combination

During early neonatal development, the future reactivity of the heart to cardiac autonomic stimulation is programmed by the timing and intensity of the arrival of parasympathetic and sympathetic inputs. In neonatal rats, we examined the effects of exposure to terbutaline, a beta-adrenoceptor (betaAR) agonist used to arrest preterm labor, and chlorpyrifos (CPF), a widely used organophosphate pesticide that acts in part through inhibition of cholinesterase, using scenarios mimicking the likely developmental stages corresponding to peak human exposures: postnatal days (PN) 2-5 for terbutaline and PN11-14 for CPF. Terbutaline evoked a progressive deficit in cardiac betaAR binding but did not interfere with the ability of the receptors to stimulate adenylyl cyclase (AC). Terbutaline also reduced expression of m2 muscarinic acetylcholine receptors and suppressed their ability to inhibit AC. Surprisingly, CPF produced similar actions, a decrement in betaAR and m2 muscarinic receptor binding and a loss of the cholinergic AC response, and also augmented the ability of betaARs to stimulate AC. The effects of CPF are thus unlikely to reside in cholinergic hyperstimulation resulting from cholinesterase inhibition but instead involve other actions converging on receptors and cell signaling. Exposure to both agents, terbutaline followed by CPF, produced a summation of the two individual effects. Our findings at the level of cell signaling thus indicate that neonatal exposure to terbutaline or CPF, or sequentially to both agents, results in an imbalance of cardiac autonomic inputs favoring increased excitability, an outcome that may have an impact on cardiovascular responses.

beta2-adrenergic receptor activation and genetic polymorphisms in autism: data from dizygotic twins

Gestational and genetic factors can contribute to autism during infancy and early childhood through their effects on fetal brain development. Previous twin studies have shown strong genetic components for the development of autism, a disorder that can have multiple causes. We investigated the effects of prenatal overstimulation of the beta2-adrenergic receptor in dizygotic twins who were exposed to terbutaline, a selective beta2-adrenergic receptor agonist used to treat premature labor, as a gestational factor. As a possible genetic mechanism, we studied two beta2-adrenergic receptor polymorphisms in twins from whom DNA was available: glycine substitution at codon 16 (16G) and glutamic acid substitution at codon 27 (27E), which show diminished desensitization in vivo compared with the wild-type receptor. Continuous terbutaline exposure for 2 weeks or longer was associated with increased concordance for autism spectrum disorders in dizygotic twins (relative risk = 2.0), with a further increase in the risk for male twins with no other affected siblings (relative risk = 4.4). A significant association was found between the presence of 16G and 27E polymorphisms in autistic patients compared with population controls (P = .006). Prenatal overstimulation of the beta2-adrenergic receptor by terbutaline or by increased signaling of genetic polymorphisms of the beta2-adrenergic receptor that have diminished desensitization can affect cellular responses and developmental programs in the fetal brain, leading to autism.

Developmental exposure to terbutaline alters cell signaling in mature rat brain regions and augments the effects of subsequent neonatal exposure to the organophosphorus insecticide chlorpyrifos

Exposure to apparently unrelated neurotoxicants can nevertheless converge on common neurodevelopmental events. We examined the long-term effects of developmental exposure of rats to terbutaline, a beta-adrenoceptor agonist used to arrest preterm labor, and the organophosphorus insecticide chlorpyrifos (CPF) separately and together. Treatments mimicked the appropriate neurodevelopmental stages for human exposures: terbutaline on postnatal days (PN) 2-5 and CPF on PN11-14, with assessments conducted on PN45. Although neither treatment affected growth or viability, each elicited alterations in CNS cell signaling mediated by adenylyl cyclase (AC), a transduction pathway shared by numerous neuronal and hormonal signals. Terbutaline altered signaling in the brainstem and cerebellum, with gender differences particularly notable in the cerebellum (enhanced AC in males, suppressed in females). By itself, CPF exposure elicited deficits in AC signaling in the midbrain, brainstem, and striatum. However, sequential exposure to terbutaline followed by CPF produced larger alterations and involved a wider spectrum of brain regions than were obtained with either agent alone. In the cerebral cortex, adverse effects of the combined treatment intensified between PN45 and PN60, suggesting that exposures alter the long-term program for development of synaptic communication, leading to alterations in AC signaling that emerge even after adolescence. These findings indicate that terbutaline, like CPF, is a developmental neurotoxicant, and reinforce the idea that its use in preterm labor may create a subpopulation that is sensitized to long-term CNS effects of organophosphorus insecticides.

Does pharmacotherapy for preterm labor sensitize the developing brain to environmental neurotoxicants? Cellular and synaptic effects of sequential exposure to terbutaline and chlorpyrifos in neonatal rats

It is increasingly clear that environmental toxicants target specific human subpopulations. In the current study, we examined the effects of prior developmental exposure to a beta(2)-adrenoceptor agonist used to arrest preterm labor, terbutaline, on the subsequent effects of exposure to the organophosphate insecticide, chlorpyrifos (CPF). Neonatal rats were given terbutaline on postnatal day (PN) 2-5, followed by CPF on PN11-14. Although neither treatment affected growth or viability, each elicited alterations in indices of brain cell differentiation and cholinergic innervation in the immediate posttreatment period (PN15), persisting into adulthood (PN60). Biomarkers of brain cell number (DNA concentration and content), cell size (protein/DNA ratio) and neuritic projections (membrane/total protein) were affected by either agent alone, with patterns consistent with neuronal and neuritic damage accompanied by reactive gliosis. The combined exposure augmented these effects by both additive and synergistic mechanisms. Similarly, choline acetyltransferase (ChAT), a constitutive marker for cholinergic nerve terminals, was affected only by combined exposure to both terbutaline and CPF. Indices of cholinergic synaptic activity [hemicholinium-3 and m(2)-muscarinic acetylcholine receptor binding] showed impairment after exposure to either terbutaline or CPF but the effects were more severe when the treatments were combined. These findings suggest that terbutaline, like CPF, is a developmental neurotoxicant, and that its use in the therapy of preterm labor may create a subpopulation that is sensitized to the adverse neural effects of a subsequent exposure to organophosphate insecticides.

β-Adrenoceptor modulation of transiently overexpressed α2-adrenoceptors in brain and peripheral tissues: cellular mechanisms underlying the developmental toxicity of terbutaline

Terbutaline, a selective beta(2)-adrenoceptor (beta(2)AR) agonist, is widely used as a tocolytic to arrest preterm labor but recent studies indicate that excessive betaAR stimulation can alter the expression and function of other neurotransmitter receptors that are essential to fetal/neonatal development. In many immature tissues, alpha(2)-adrenergic receptors (alpha(2)ARs) are overexpressed and the receptors are thought to play a role in cell proliferation and architectural assembly. We evaluated whether betaAR agonists perturb the expression of alpha(2)ARs in central and peripheral tissues during various developmental stages in the fetal and neonatal rat. In peripheral tissues (heart, liver, kidney) administration of terbutaline (10mg/kg s.c. for 4 days) elicited decrements in alpha(2)AR expression only during a critical developmental window that differed for each tissue; terbutaline was more effective than isoproterenol, a mixed beta(1)/beta(2) agonist. Neonatal destruction of sympathetic nerves with 6-hydroxydopamine (6-OHDA) had a biphasic effect, initially reducing alpha(2)ARs but subsequently elevating receptor expression. In contrast to the effects in the periphery, terbutaline administration promoted alpha(2)AR expression in neonatal brain regions with effects preferential to males. As the rat is an altricial species, these results during late gestation and the early neonatal period indicate that betaAR input modulates alpha(2)AR expression during developmental stages in which betaAR tocolytics are likely to be used. Disruption of alpha(2)AR expression and function may therefore contribute to adverse effects that have been noted in the offspring of pregnant women treated with terbutaline.

Does terbutaline damage the developing heart?

BACKGROUND

Beta(2)-Adrenoceptor (betaAR) agonists, such as terbutaline, are widely used to arrest preterm labor. They also cross the placenta where they stimulate receptors in fetal tissues, which in turn use betaAR input for trophic control of cell replication and differentiation.

METHODS

As rats are altricial, we administered terbutaline in two different postnatal exposure periods (10 mg/kg given daily on Days 2-5 or 11-14).

RESULTS

Hearts were examined twenty-four hours after the last dose and on postnatal day 30 for cardiac damage. Neither treatment paradigm caused an increase in cardiac abnormalities compared to controls but quantitative analysis of the number of nuclei indicated reductions in females.

CONCLUSIONS

These findings do not support earlier case reports of outright myocardial necrosis after terbutaline tocolysis in human infants. Nevertheless, the significant statistical association between terbutaline and cardiac anomalies in epidemiological studies suggest that terbutaline may sensitize the developing heart to other insults that affect development.

Terbutaline Is a Developmental Neurotoxicant: Effects on Neuroproteins and Morphology in Cerebellum, Hippocampus, and Somatosensory Cortex

Beta(2)-adrenoceptor agonists, especially terbutaline, are widely used to arrest preterm labor, but they also cross the placenta to stimulate fetal beta-adrenoceptors that control neural cell differentiation. We evaluated the effects of terbutaline administration in neonatal rats, a stage of neurodevelopment corresponding to human fetal development. Terbutaline administered on postnatal days PN2 to 5 elicited neurochemical changes indicative of neuronal injury and reactive gliosis: immediate increases in glial fibrillary acidic protein and subsequent induction of the 68-kDa neurofilament protein. Quantitative morphological evaluations carried out on PN30 indicated structural abnormalities in the cerebellum, hippocampus, and somatosensory cortex. In the cerebellum, PN2 to 5 terbutaline treatment reduced the number of Purkinje cells and elicited thinning of the granular and molecular layers. The hippocampal CA3 region also displayed thinning, along with marked gliosis, effects that were restricted to females. In the somatosensory cortex, terbutaline evoked a reduction in the proportion of pyramidal cells and an increase in smaller, nonpyramidal cells; again, females were affected more than males. Although abnormalities were obtained with later terbutaline treatment (PN11 to 14), in general the effects were smaller than those seen with PN2 to 5 exposure. Our results indicate that terbutaline is a neurotoxicant that elicits biochemical alterations and structural damage in the immature brain during a critical period. These effects point to a causal relationship between fetal terbutaline exposure and the higher incidence of cognitive and neuropsychiatric disorders reported for the offspring of women receiving terbutaline therapy for preterm labor.

Developmental toxicity of terbutaline: critical periods for sex-selective effects on macromolecules and DNA synthesis in rat brain, heart, and liver

beta-Adrenoceptors (betaARs) control cell replication/differentiation, and during development, signaling is not subject to desensitization. We examined the effects of terbutaline, a beta(2)AR agonist used as a tocolytic, on development in rat brain regions and peripheral tissues with high betaAR concentrations. Prenatal terbutaline (gestational days 17-20) decreased cell numbers (DNA content) in the fetal brain and liver. Early postnatal exposure (PN2-5) reduced DNA synthesis in early-developing brain regions of females, with sensitization of the effect upon repeated terbutaline administration; after multiple terbutaline injections, DNA content was reduced in male cerebellum. The cerebellum was targeted later (PN11-14), exhibiting decreased DNA synthesis in both sexes; in contrast, cardiac DNA synthesis decreased after one injection but increased after the fourth daily injection. Our results suggest that excessive betaAR stimulation by terbutaline alters cell development in brain regions and peripheral tissues, with the net effect depending on sex and the timing of exposure. These effects may contribute to neuropsychiatric, cognitive, cardiovascular, and metabolic abnormalities reported in the offspring of women treated with beta-agonist tocolytics.

Beta-adrenoceptor signaling in the developing brain: sensitization or desensitization in response to terbutaline

Beta(2)-adrenoceptor agonists are commonly used to arrest preterm labor but they also penetrate the placenta to stimulate fetal beta-adrenergic receptors (betaAR), and have been implicated in subsequent neurobehavioral deficits. We administered terbutaline to pregnant rats on gestational days (GD) 17-20 and during two postnatal (PN) periods, PN2-5 and PN11-14, that correspond to third trimester human neurological development. We then examined betaAR binding sites and adenylyl cyclase (AC) signaling in fetal brain or neonatal brain regions. Although fetal terbutaline administration evoked betaAR downregulation, the ability of isoproterenol to stimulate AC was enhanced instead of desensitized. Sensitization occurred at post-receptor signaling proteins, as augmented responses were also seen for stimulants that bypass the receptors to work on G-proteins (NaF) or that stimulate AC directly (forskolin and Mn(2+)). When terbutaline was given on PN2-5, betaAR downregulation was obtained in brainstem, forebrain and cerebellum, but desensitization of the AC response was seen only in the forebrain; the desensitization was heterologous, reflecting decrements in total AC activity rather than specific loss of the betaAR response. With treatment on PN11-14, only the cerebellum showed betaAR downregulation and induction at the level of post-receptor signaling proteins maintained the betaAR-mediated AC response. Our results indicate that, unlike the adult, betaAR signaling in the fetus and neonate is resistant to homologous desensitization by beta-agonists, and in fact, displays heterologous sensitization that sustains or enhances the overall response. The inability to desensitize betaAR responses may lead to disruption of neural cell development as a consequence of tocolytic therapy.

Regulation of fetal cardiac and hepatic beta-adrenoceptors and adenylyl cyclase signaling: terbutaline effects

Terbutaline (Ter), a beta(2)-adrenergic agonist used in preterm labor, stimulates fetal beta-adrenoceptors (beta-ARs). We administered Ter to pregnant rats on gestational days 17-20 and examined beta-ARs and adenylyl cyclase (AC) signaling in heart and liver. Ter produced less downregulation of cardiac beta-ARs than in adults, despite a higher proportion of the beta(2)-subtype, and failed to elicit desensitization of the receptor-mediated AC response. AC stimulants acting at different points indicated an offsetting of homologous desensitization at the level of the beta-AR by heterologous sensitization at the level of AC: induction of total AC catalytic activity and a shift in the catalytic profile or AC isoform. In fetal liver, Ter produced downregulation of beta-ARs, in keeping with the predominance of the beta(2)-subtype; hepatic receptor downregulation was equivalent in fetus and adult. Nevertheless, there was still no desensitization of beta-AR-mediated AC responses and again AC was induced. Our results indicate that, unlike in the adult, fetal beta-AR signaling is not desensitized by beta-agonists and, in fact, displays heterologous sensitization, thus sustaining responses during parturition. At the same time, the inability to desensitize beta-AR AC responses may lead to disruption of cardiac, hepatic, or neural cell development as a consequence of tocolytic therapy with beta-agonists.