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Impact of In-Utero Dexamethasone on Autonomic Regulation in Adulthood

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Premature babies are at risk of death from immature lung development. For this reason, pregnant mothers at risk for preterm delivery are administered dexamethasone (DEX), a synthetic glucocorticoid that promotes fetal lung development. However, exposure to DEX in utero is

Premature babies are at risk of death from immature lung development. For this reason, pregnant mothers at risk for preterm delivery are administered dexamethasone (DEX), a synthetic glucocorticoid that promotes fetal lung development. However, exposure to DEX in utero is associated with low birth weight and cardiovascular development pathologies. Moreover, our lab found that DEX administration in-utero leads to a sex-specific increase in stress-induced tachycardia in female, but not male offspring. This project seeks to expand on this preliminary finding of the heart by examining local effectors of activity from the sympathetic system (tyrosine hydroxylase and catechol-o-methyltransferase). Tyrosine hydroxylase was measured as it catalyzes the rate limiting step of norepinephrine synthesis while catechol-O- methyltransferase was studied as it catalyzes the degradation of norepinephrine. Acetylcholinesterase was used to measure parasympathetic activity as it catalyzes the degradation of the primary neurotransmitter of the parasympathetic nervous system, acetylcholine. Analyses of sympathetic as well as parasympathetic activity were done to determine influences of in-utero DEX exposure on autonomic regulation in adulthood. Pregnant rats were administered DEX (0.4 mg/kg, i.p.) or vehicle (20% w/v 2-hydroxypropyl ß- cyclodextran) at gestation days 18-21, with euthanasia of offspring occurring at around the time the offspring reached 13-15 weeks of age. Left ventricles and right atria were pulverized, processed and subjected to western blot analysis to determine expression of proteins of interest. Males exposed to DEX in-utero saw a decrease in tyrosine hydroxylase expression in left ventricle and right atrium when compared to vehicle control, a difference not seen with females. In addition, catechol-o-methyltransferase expression was increased in right atria from male, but not female rats. Acetylcholinesterase expression was reduced in the right atria of female, but not male rats. The present findings suggest reduced norepinephrine signaling in the heart of male, but not female DEX-exposed offspring. Given that we have previously found that female, but not male rats exhibit exaggerated stress-induced tachycardia, our current findings suggest that males possess a sex-specific compensatory mechanism allowing the heart to resist increased sympathetic signaling from the brain, one that females do not possess. The underlying mechanics of this proposed mechanism are unclear, and further investigation is needed in this subject to determine the significance of the findings from our study.

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2021-05

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Prenatal stress and infant regulatory capacity

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The development of self-regulation is believed to play a crucial role in predicting later psychopathology and is believed to begin in early childhood. The early postpartum period is particularly important in laying the groundwork for later self-regulation as infants' dispositional

The development of self-regulation is believed to play a crucial role in predicting later psychopathology and is believed to begin in early childhood. The early postpartum period is particularly important in laying the groundwork for later self-regulation as infants' dispositional traits interact with caregivers' co-regulatory behaviors to produce the earliest forms of self-regulation. Moreover, although emerging literature suggests that infants' exposure to maternal stress even before birth may be integral in determining children's self-regulatory capacities, the complex pathways that characterize these developmental processes remain unclear. The current study considers the complex, transactional processes in a high-risk, Mexican American sample. Data were collected from 305 Mexican American infants and their mothers during prenatal, 6- and 12-week home interviews. Mother self-reports of stress were obtained prenatally between 34-37 weeks gestation. Mother reports of infant temperamental negativity and surgency were obtained at 6-weeks as were observed global ratings of maternal sensitivity during a structured peek-a-boo task. Microcoded ratings of infants' engagement orienting and self-comforting behaviors were obtained during the 12-week peek-a-boo task. Study findings suggest that self-comforting and orienting behaviors help to modulate infants' experiences of distress, and also that prenatal stress influences infants' engagement in each of those regulatory behaviors, both directly by influence tendencies to engage in orienting behaviors and indirectly by programming higher levels of infant negativity and surgency, both of which may confer risk for later regulatory disadvantage. Advancing our understandings about the nature of these developmental pathways could have significant implications for targets of early intervention in this high-risk population.

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2013