Newborn cerebrovascular responses after first trimester moderate maternal ethanol exposure in sheep

Vascular Contributions to the Neurobiological Effects of Prenatal Alcohol Exposure

Fetal alcohol spectrum disorders (FASD) are often characterized as a cluster of brain-based disabilities. Though cardiovascular effects of prenatal alcohol exposure (PAE) have been documented, the vascular deficits due to PAE are less understood, but may contribute substantially to the severity of neurobehavioral presentation and health outcomes in persons with FASD.

Methods

We conducted a systematic review of research articles curated in PubMed to assess the strength of the research on vascular effects of PAE. 40 pertinent papers were selected, covering studies in both human populations and animal models.

Results

Studies in human populations identified cardiac defects, and defects in vasculature, including increased tortuosity, defects in basement membranes, capillary basal hyperplasia, endarteritis, and disorganized and diminished cerebral vasculature due to PAE. Preclinical studies showed that PAE rapidly and persistently results in vasodilation of large afferent cerebral arteries, but to vasoconstriction of smaller cerebral arteries and microvasculature. Moreover, PAE continues to affect cerebral blood flow into middle-age. Human and animal studies also indicate that ocular vascular parameters may have diagnostic and predictive value. A number of intervening mechanisms were identified, including increased autophagy, inflammation and deficits in mitochondria. Studies in animals identified persistent changes in blood flow and vascular density associated with endocannabinoid, prostacyclin and nitric oxide signaling, as well as calcium mobilization.

Conclusion

Although the brain has been a particular focus of studies on PAE, the cardiovascular system is equally affected. Studies in human populations, though constrained by small sample sizes, did link pathology in major blood vessels and tissue vasculature, including brain vasculature, to PAE. Animal studies highlighted molecular mechanisms that may be useful therapeutic targets. Collectively, these studies suggest that vascular pathology is a possible contributing factor to neurobehavioral and health problems across a lifespan in persons with a diagnosis of FASD. Furthermore, ocular vasculature may serve as a biomarker for neurovascular health in FASD.

Prenatal exposure to alcohol: mechanisms of cerebral vascular damage and lifelong consequences

Alcohol is a well-known teratogen, and prenatal alcohol exposure (PAE) leads to a greater incidence of many cardiovascular-related pathologies. Alcohol negatively impacts vasculogenesis and angiogenesis in the developing fetal brain, resulting in fetal alcohol spectrum disorders (FASD). Ample preclinical evidence indicates that the normal reactivity of cerebral resistance arterioles, which regulate blood flow distribution in response to metabolic demand (neurovascular coupling), is impaired by PAE. This impairment of dilation of cerebral arteries may carry implications for the susceptibility of the brain to cerebral ischemic damage well into adulthood. The focus of this review is to consolidate findings from studies examining the influence of PAE on vascular development, give insights into relevant pathological mechanisms at the vascular level, evaluate the risks of ethanol-driven alterations of cerebrovascular reactivity, and revisit different preventive interventions that may have promise in reversing vascular changes in preclinical FASD models.

MicroRNA-150-5p is upregulated in the brain microvasculature during prenatal alcohol exposure and inhibits the angiogenic factor Vezf1

BACKGROUND

Fetal alcohol spectrum disorders (FASD) occur in children who were exposed to alcohol in utero and are manifested in a wide range of neurocognitive deficits. These deficits could be caused by alterations to the cortical microvasculature that are controlled by post-transcriptional regulators such as microRNAs.

METHODS

Using an established mouse model of moderate prenatal alcohol exposure (PAE), we isolated cortices (CTX) and brain microvascular endothelial cells (BMVECs) at embryonic day 18 (E18) and examined the expression of miR-150-5p and potential downstream targets. Cellular transfections and intrauterine injections with LNA™ mimics or inhibitors were used to test miR-150-5p regulation of novel target vascular endothelial zinc finger 1 (Vezf1). Dual-luciferase assays were used to assess the direct binding of miR-150-5p to the Vezf1 3'UTR. The effects of miR-150-5p and Vezf1 on endothelial cell function were determined by in vitro migration and tube formation assays.

RESULTS

We found that miR-150-5p was upregulated and Vezf1 was downregulated during PAE in the E18 CTX and BMVECs. Transfection with miR-150-5p mimics resulted in decreased Vezf1 expression in BMVECs, while miR-150-5p inhibition did the opposite. Dual-luciferase assays revealed direct binding of miR-150-5p with the Vezf1 3'UTR. Intrauterine injections showed that miR-150-5p regulates the expression of Vezf1 in vivo during PAE. miR-150-5p overexpression decreased BMVEC migration and tube formation, while miR-150-5p inhibition enhanced migration and tube formation. Vezf1 overexpression rescued the effects of the miR-150-5p mimic. Alcohol treatment of BMVECs increased miR-150-5p expression and inhibited migration and tube formation. Finally, miR-150-5p inhibition and Vezf1 overexpression rescued the negative effects of alcohol on migration and tube formation.

CONCLUSIONS

miR-150-5p regulation of Vezf1 results in altered endothelial cell function during alcohol exposure. Further, miR-150-5p inhibition of Vezf1 may adversely alter the development of the cortical microvasculature during PAE and contribute to deficits seen in patients with FASD.

Prenatal Exposure to Tobacco and Alcohol Alters Development of the Neonatal Auditory System

Prenatal exposures to alcohol (PAE) and tobacco (PTE) are known to produce adverse neonatal and childhood outcomes including damage to the developing auditory system. Knowledge of the timing, extent, and combinations of these exposures on effects on the developing system is limited. As part of the physiological measurements from the Safe Passage Study, Auditory Brainstem Responses (ABRs) and Transient Otoacoustic Emissions (TEOAEs) were acquired on infants at birth and one-month of age. Research sites were in South Africa and the Northern Plains of the U.S. Prenatal information on alcohol and tobacco exposure was gathered prospectively on mother/infant dyads. Cluster analysis was used to characterize three levels of PAE and three levels of PTE. Repeated-measures ANOVAs were conducted for newborn and one-month-old infants for ABR peak latencies and amplitudes and TEOAE levels and signal-to-noise ratios. Analyses controlled for hours of life at test, gestational age at birth, sex, site, and other exposure. Significant main effects of PTE included reduced newborn ABR latencies from both ears. PTE also resulted in a significant reduction of ABR peak amplitudes elicited in infants at 1-month of age. PAE led to a reduction of TEOAE amplitude for 1-month-old infants but only in the left ear. Results indicate that PAE and PTE lead to early disruption of peripheral, brainstem, and cortical development and neuronal pathways of the auditory system, including the olivocochlear pathway.

Rosiglitazone restores nitric oxide synthase-dependent reactivity of cerebral arterioles in rats exposed to prenatal alcohol

BACKGROUND

Prenatal exposure to alcohol leads to a greater incidence of many cardiovascular-related diseases, presumably via a mechanism that may involve increased oxidative stress. An agonist of peroxisome proliferator-activated receptor gamma (PPARγ; rosiglitazone) has been shown to suppress alcohol-induced neuroinflammation and oxidative stress. The goal of this study was to determine whether acute and chronic treatment with rosiglitazone could restore or prevent impaired nitric oxide synthase (NOS)-dependent responses of cerebral arterioles in male and female adult (14-16 weeks old) rats exposed to alcohol in utero.

METHODS

We fed Sprague-Dawley dams a liquid diet with or without 3% ethanol for the duration of their pregnancy (21-23 days). In the first series of studies, we examined the reactivity of cerebral arterioles to eNOS- (ADP), nNOS-dependent (NMDA), and NOS-independent agonists in male and female adult rats before and during acute (1 hour) topical application of rosiglitazone (1 µM). In a second series of studies, we examined the influence of chronic treatment with rosiglitazone (3 mg/kg/day in drinking water for 2-3 weeks) on the responses of cerebral arterioles in male and female adult rats exposed to alcohol in utero.

RESULTS

We found that in utero exposure to alcohol similarly reduced responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in male and female adult rats. In addition, acute treatment of the male and female adult rats with rosiglitazone similarly restored this impairment in cerebral vascular function to that observed in controls. We also found that chronic treatment with rosiglitazone prevented impaired vascular function in male and female adult rats that were exposed to alcohol in utero.

CONCLUSIONS

PPARγ activation may be an effective and relevant treatment to reverse or prevent cerebral vascular abnormalities associated with prenatal exposure to alcohol.

In Utero Exposure to Alcohol Impairs Reactivity of Cerebral Arterioles and Increases Susceptibility of the Brain to Damage Following Ischemia/Reperfusion in Adulthood

BACKGROUND

Maternal consumption of alcohol produces abnormalities in the developing fetus and can contribute to an increased incidence of many cardiovascular-related diseases. The first goal of this study was to determine whether in utero exposure to alcohol influences reactivity of cerebral arterioles in adult (12 to 15 weeks old) rats. The second goal of this study was to examine whether in utero exposure to alcohol increased the susceptibility of the brain to damage following an ischemic event in adult rats.

METHODS

We fed Sprague Dawley dams a liquid diet with or without alcohol (3% ethanol) for the duration of their pregnancy (21 to 23 days). In the first series of studies, we examined reactivity of cerebral arterioles to endothelial nitric oxide synthase (eNOS)- (adenosine diphosphate [ADP]) and neuronal nitric oxide synthase (nNOS)-dependent N-methyl-D-aspartate (NMDA, and NOS-independent agonists in adult rats before and during application of l-NMMA. In another series of studies, we examined infarct volume following middle cerebral artery occlusion in adult offspring exposed to alcohol in utero. In both series of studies, we also determined the role for an increase in oxidative stress by feeding dams apocynin for the duration of their pregnancy.

RESULTS

We found that in utero exposure to alcohol reduced responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in adult rats. In addition, treatment of the dams with apocynin prevented this impairment in cerebral vascular function. We also found that in utero exposure to alcohol worsened brain damage following ischemia/reperfusion in adult rats and that treatment of dams with apocynin prevented this increase in brain damage following ischemia/reperfusion.

CONCLUSIONS

We suggest that our findings may have important implications for the pathogenesis of brain abnormalities associated with fetal alcohol exposure.

In utero exposure to alcohol alters reactivity of cerebral arterioles

Our goal was to examine whether in utero exposure to alcohol impaired reactivity of cerebral arterioles during development. We fed Sprague-Dawley dams a liquid diet with or without alcohol (3% ethanol) for the duration of pregnancy (21-23 days). Around 4-6 weeks after birth, we examined reactivity of cerebral arterioles to eNOS- (ADP) and nNOS-dependent (NMDA) agonists in the offspring. We found that in utero exposure to alcohol attenuated responses of cerebral arterioles to ADP and NMDA, but not to nitroglycerin in rats exposed to alcohol in utero. L-NMMA reduced responses to agonists in control rats, but not in rats exposed to alcohol in utero. Treatment of dams with apocynin for the duration of pregnancy rescued the impairment in reactivity to ADP and NMDA in the offspring. Protein expression of NOX-2 and NOX-4 was increased in alcohol rats compared to control rats. We also found an increase in superoxide levels in the cortex of rats exposed to alcohol in utero. Our findings suggest that in utero exposure to alcohol impairs eNOS and nNOS reactivity of cerebral arterioles via a chronic increase in oxidative stress.

Fetal Cerebral Circulation as Target of Maternal Alcohol Consumption

Alcohol (ethanol [EtOH]) is one of the most widely used psychoactive substances worldwide. Alcohol consumption during pregnancy may result in a wide range of morphological and neurodevelopmental abnormalities termed fetal alcohol spectrum disorders (FASD), with the most severe cases diagnosed as fetal alcohol syndrome (FAS). FAS and FASD are not readily curable and currently represent the leading preventable causes of birth defect and neurodevelopmental delay in the United States. The etiology of FAS/FASD remains poorly understood. This review focuses on the effects of prenatal alcohol exposure (PAE) on fetal cerebrovascular function. A brief introduction to the epidemiology of alcohol consumption and the developmental characteristics of fetal cerebral circulation is followed by several sections that discuss current evidence documenting alcohol-driven alterations of fetal cerebral blood flow, artery function, and microvessel networks. The material offers mechanistic insights at the vascular level itself into the pathophysiology of PAE.

Investigation of circle of Willis variants and hemodynamic parameters in twins using transcranial color-coded Doppler sonography

Morphological and hemodynamic variations of the circle of Willis (CW) may have an important impact on cerebrovascular events. However, the environmental and genetic influence remains unclear. For this reason we studied the variations and hemodynamic parameters of the CW in twins using transcranial color-coded sonography (TCCS). Sixty-four twins, 19 monozygotic (MZ) and 13 dizygotic (DZ) pairs from the Italian Twin Registry (average age 45.0 ± 13.7 years) underwent TCCS and risk factor assessment. We examined CW morphology and recorded peak systolic velocity (PSV), end-diastolic velocity (EDV) and pulsatility index (PI). Raw heritability was determined for hemodynamic parameters, whereas concordance and discordance rates were calculated for CW morphological variants. A normal CW anatomy was observed in the majority of MZ and DZ twins (76.5% and 92.3%, respectively). The most frequent variant was a missing anterior cerebral artery (ACA). There was no significant difference in the prevalence of most CW variants depending on the zigosity. Concordance rates were low regarding the presence of variant CW anatomy both in MZ and DZ groups (0.14 and 0.00, respectively). Women had a significantly higher PI in vertebral arteries (VA) and in the right ACA (p = 0.01, p = 0.02 and p < 0.01, respectively). An inverse correlation was observed between hemodynamic parameters and age. Morphological variants of the CW do not seem to be heritable; they are most likely determined by environmental factors. In contrast, hemodynamic parameters of the CW are moderately heritable and this might have implications in the management and prevention of cerebrovascular diseases.

Meta-Analysis of Gene Expression Patterns in Animal Models of Prenatal Alcohol Exposure Suggests Role for Protein Synthesis Inhibition and Chromatin Remodeling

BACKGROUND

Prenatal alcohol exposure (PAE) can result in an array of morphological, behavioral, and neurobiological deficits that can range in their severity. Despite extensive research in the field and a significant progress made, especially in understanding the range of possible malformations and neurobehavioral abnormalities, the molecular mechanisms of alcohol responses in development are still not well understood. There have been multiple transcriptomic studies looking at the changes in gene expression after PAE in animal models; however, there is a limited apparent consensus among the reported findings. In an effort to address this issue, we performed a comprehensive re-analysis and meta-analysis of all suitable, publically available expression data sets.

METHODS

We assembled 10 microarray data sets of gene expression after PAE in mouse and rat models consisting of samples from a total of 63 ethanol (EtOH)-exposed and 80 control animals. We re-analyzed each data set for differential expression and then used the results to perform meta-analyses considering all data sets together or grouping them by time or duration of exposure (pre- and postnatal, acute and chronic, respectively). We performed network and Gene Ontology enrichment analysis to further characterize the identified signatures.

RESULTS

For each subanalysis, we identified signatures of differential expressed genes that show support from multiple studies. Overall, the changes in gene expression were more extensive after acute EtOH treatment during prenatal development than in other models. Considering the analysis of all the data together, we identified a robust core signature of 104 genes down-regulated after PAE, with no up-regulated genes. Functional analysis reveals over representation of genes involved in protein synthesis, mRNA splicing, and chromatin organization.

CONCLUSIONS

Our meta-analysis shows that existing studies, despite superficial dissimilarity in findings, share features that allow us to identify a common core signature set of transcriptome changes in PAE. This is an important step to identifying the biological processes that underlie the etiology of fetal alcohol spectrum disorders.

Effects of L-glutamine supplementation on maternal and fetal hemodynamics in gestating ewes exposed to alcohol

Not much is known about effects of gestational alcohol exposure on maternal and fetal cardiovascular adaptations. This study determined whether maternal binge alcohol exposure and L-glutamine supplementation could affect maternal-fetal hemodynamics and fetal regional brain blood flow during the brain growth spurt period. Pregnant sheep were randomly assigned to one of four groups: saline control, alcohol (1.75-2.5 g/kg body weight), glutamine (100 mg/kg body weight) or alcohol + glutamine. A chronic weekend binge drinking paradigm between gestational days (GD) 99 and 115 was utilized. Fetuses were surgically instrumented on GD 117 ± 1 and studied on GD 120 ± 1. Binge alcohol exposure caused maternal acidemia, hypercapnea, and hypoxemia. Fetuses were acidemic and hypercapnic, but not hypoxemic. Alcohol exposure increased fetal mean arterial pressure, whereas fetal heart rate was unaltered. Alcohol exposure resulted in ~40 % reduction in maternal uterine artery blood flow. Labeled microsphere analyses showed that alcohol induced >2-fold increases in fetal whole brain blood flow. The elevation in fetal brain blood flow was region-specific, particularly affecting the developing cerebellum, brain stem, and olfactory bulb. Maternal L-glutamine supplementation attenuated alcohol-induced maternal hypercapnea, fetal acidemia and increases in fetal brain blood flow. L-Glutamine supplementation did not affect uterine blood flow. Collectively, alcohol exposure alters maternal and fetal acid-base balance, decreases uterine blood flow, and alters fetal regional brain blood flow. Importantly, L-glutamine supplementation mitigates alcohol-induced acid-base imbalances and alterations in fetal regional brain blood flow. Further studies are warranted to elucidate mechanisms responsible for alcohol-induced programming of maternal uterine artery and fetal circulation adaptations in pregnancy.

Maternal alcohol consumption in pregnancy enhances arterial stiffness and alters vasodilator function that varies between vascular beds in fetal sheep

While the impact of alcohol consumption by pregnant women on fetal neurodevelopment has received much attention, the effects on the cardiovascular system are not well understood. We hypothesised that repeated exposure to alcohol (ethanol) in utero would alter fetal arterial reactivity and wall stiffness, key mechanisms leading to cardiovascular disease in adulthood. Ethanol (0.75 g (kg body weight)(-1)) was infused intravenously into ewes over 1 h daily for 39 days in late pregnancy (days 95-133 of pregnancy, term ∼147 days). Maternal and fetal plasma ethanol concentrations at the end of the hour were ∼115 mg dl(-1), and then declined to apparent zero over 8 h. At necropsy (day 134), fetal body weight and fetal brain-body weight ratio were not affected by alcohol infusion. Small arteries (250-300 μm outside diameter) from coronary, renal, mesenteric, femoral (psoas) and cerebral beds were isolated. Endothelium-dependent vasodilatation sensitivity was reduced 10-fold in coronary resistance arteries, associated with a reduction in endothelial nitric oxide synthase mRNA (P = 0.008). Conversely, vasodilatation sensitivity was enhanced 10-fold in mesenteric and renal resistance arteries. Arterial stiffness was markedly increased (P = 0.0001) in all five vascular beds associated with an increase in elastic modulus and, in cerebral vessels, with an increase in collagen Iα mRNA. Thus, we show for the first time that fetal arteries undergo marked and regionally variable adaptations as a consequence of repeated alcohol exposure. These alcohol-induced vascular effects occurred in the apparent absence of fetal physical abnormalities or fetal growth restriction.

Long-term consequences of developmental alcohol exposure on brain structure and function: therapeutic benefits of physical activity

Developmental alcohol exposure both early in life and during adolescence can have a devastating impact on normal brain structure and functioning, leading to behavioral and cognitive impairments that persist throughout the lifespan. This review discusses human work as well as animal models used to investigate the effect of alcohol exposure at various time points during development, as well as specific behavioral and neuroanatomical deficits caused by alcohol exposure. Further, cellular and molecular mediators contributing to these alcohol-induced changes are examined, such as neurotrophic factors and apoptotic markers. Next, this review seeks to support the use of aerobic exercise as a potential therapeutic intervention for alcohol-related impairments. To date, few interventions, behavioral or pharmacological, have been proven effective in mitigating some alcohol-related deficits. Exercise is a simple therapy that can be used across species and also across socioeconomic status. It has a profoundly positive influence on many measures of learning and neuroplasticity; in particular, those measures damaged by alcohol exposure. This review discusses current evidence that exercise may mitigate damage caused by developmental alcohol exposure and is a promising therapeutic target for future research and intervention strategies.

Prenatal alcohol exposure: implications for cardiovascular function in the fetus and beyond

1. The effects of heavy maternal alcohol consumption during pregnancy on cognitive and behavioural performance and craniofacial malformations in the offspring have been studied extensively. In contrast, the impact of maternal alcohol intake on the cardiovascular system of the offspring and the effects of more modest consumption have received very scant consideration. 2. Adverse conditions in the pre- and neonatal periods can have a profound legacy on offspring health, including the risk of cardiovascular disease. Prenatal alcohol exposure can modulate vascular reactivity, including endothelial and smooth muscle function. 3. Other effects of prenatal alcohol exposure are emerging, including impairment of nephrogenesis and kidney function and increased arterial stiffness. The impact of even modest prenatal alcohol exposure on cardiovascular health in the offspring remains to be determined. 4. It is envisaged that the culmination of reduced renal and vascular capacity will render the offspring more vulnerable to cardiovascular disease with ageing and exposure to additional insults and lifestyle factors.

The effects of binge alcohol exposure in the 2nd trimester on the estimated density of cerebral microvessels in near-term fetal sheep

Heavy fetal alcohol exposure is associated with a spectrum of neurological abnormalities, although the mechanism of injury is largely unknown. We previously reported attenuated cerebral blood flow response to hypoxia in fetal and newborn sheep which were exposed to alcohol earlier in pregnancy. One possible mechanism for this effect of alcohol on the developing cerebral vasculature is a decrease in cerebral microvessel density, similar to its effect on developing neurons. Therefore, we tested the hypothesis that prenatal alcohol exposure decreases cerebral microvessel density. Pregnant ewes received intravenous infusions of ethanol or saline during days 60-84 of gestation (term=150 days) and at 125 days of gestation we obtained the fetal brains for study. We immunohistochemically labeled vessels of the left cerebral forebrain hemispheres with antibody to endothelial nitric oxide synthase and then obtained unbiased stereological estimates of cerebral microvessel density using a modified optical fractionator method. We studied 20 fetal brains of which 9 were alcohol-exposed, 11 were saline-controls, and all were products of a twin gestation. Although brain and body weights were not different between groups, the alcohol-exposed group had significantly lower brain weight as a percentage of body weight. Estimates of cerebral microvessel density were not significantly different between alcohol-exposed and saline-control groups: 12.7+/-8.7 and 9.1+/-2.8 microvessels per mm(3), respectively (mean+/-SD, p=0.32). Since there is no change in estimated cerebral microvessel density after prenatal alcohol exposure, we conclude that decreased cerebral microvessel density is not a likely explanation for attenuated cerebral blood flow in response to hypoxia.

Effects of binge alcohol exposure in the second trimester on intracerebral arteriolar function in third trimester fetal sheep

Fetal alcohol syndrome is a leading cause of mental retardation, but mechanisms of alcohol-associated brain damage remain elusive. Chronic alcohol exposure attenuates fetal and neonatal hypoxic cerebral vasodilation in sheep. We therefore hypothesized that alcohol could alter development of cerebrovascular responses to adenosine, a putative mediator of hypoxic cerebral vasodilation. The objective of this study was to examine the effect of earlier fetal alcohol exposure on later reactivity to adenosine in fetal sheep cerebral arterioles. Penetrating intracerebral arterioles were harvested from the brains of third trimester fetal sheep previously exposed in the second trimester to maternal alcohol "binges" (1.5 g/kg IV over 90 min, 5 days/week for 4 weeks) or same-volume saline infusions. Arterioles were cannulated with a micropipette system and luminally pressurized. Fetal alcohol exposure did not affect spontaneous myogenic tone, but enhanced the dilator response of penetrating arterioles to extraluminal acidosis (pH 6.8). Alcohol exposure also resulted in an increase in maximal vessel response to CGS-21680, an adenosine A2A receptor agonist, but did not alter the concentration-dependent response curves to adenosine. Our results suggest that earlier alcohol exposure does not impair the subsequent responsiveness of fetal cerebral arterioles to vasodilator agents. Thus, alteration in cerebral vascular response to hypoxia in fetal sheep may not be attributed to changes in vascular reactivity to adenosine.

Fetal alcohol exposure alters cerebrovascular reactivity to vasoactive intestinal peptide in adult sheep

Chronic fetal alcohol exposure impairs neural and vascular development. We have previously shown that fetal alcohol exposure is associated with attenuated hypoxic cerebral vasodilation and reduced neuronal vasoactive intestinal peptide (VIP) expression in fetal sheep. In the present study, we tested the hypothesis that fetal alcohol exposure alters vascular development, leading to altered cerebral vascular reactivity to VIP in adulthood. Penetrating intracerebral arterioles were harvested from the brains of adult (10-13 months old) offspring of ewes that had received intravenous infusions of alcohol (1.5 g/kg) or same-volume saline (90 min/day, 5 days/week) during days 30-82 of gestation (full term = 145 days). The isolated arterioles were cannulated with a micropipette system that allowed luminal perfusion and control of luminal pressure and developed spontaneous tone at 40 degrees C and 60 mm Hg luminal pressure. There was no difference in myogenic tone between arterioles exposed prenatally to alcohol (n = 18) and saline controls (n = 17). However, fetal alcohol exposure significantly (p = 0.03) enhanced the dilator responses of adult intracerebral arterioles to VIP [0.1 nM to 1 microM, logEC(50): -8.6 +/- 0.2 (alcohol) vs. -7.4 +/- 0.8 (saline)]. In contrast, there was no difference in dilator responses to H(+) (pH 6.8 buffer), to adenosine (10 nM to 0.1 mM), or to CGS21680 (an adenosine A(2A) receptor agonist, 0.01 nM to 10 microM). Thus, fetal alcohol exposure alters vasomotor sensitivity to VIP in adult intracerebral arterioles - perhaps a compensatory response to alcohol-induced underdevelopment of neurotransmitter pathways involved in cerebral vascular regulation.

The effect of binge fetal alcohol exposure on the number of vasoactive intestinal peptide-producing neurons in fetal sheep brain

Previously we demonstrated that fetal alcohol exposure attenuates hypoxic cerebral vasodilation in fetal and neonatal sheep. One mechanism may be altered expression of brain vasoactive substances. We hypothesized that early fetal alcohol exposure alters the number of fetal neurons expressing vasoactive intestinal peptide (VIP), a potent cerebral vasodilator. Thirteen pregnant ewes received daily i.v. infusions of alcohol (1.5 g/kg) or saline on days 30-54 of gestation (term = 145 days). Fourteen fetal brains (6 alcohol-exposed, 8 saline control) were obtained on gestational day 126. Using unbiased stereology, we counted immunohistochemically-labeled VIP neurons in one half of each forebrain with an optical fractionator. The total NeuN-labeled neurons were similarly counted. Alcohol-exposed fetal sheep brains had fewer VIP-immunopositive neurons per hemisphere, 14.6 x 10(6), compared to saline controls, 19.8 x 10(6). The total neuron number was not different, 1.19 x 10(9) versus 1.23 x 10(9) respectively, indicating a selective decrease in VIP neurons as a result of alcohol exposure. In sheep, alcohol exposure early in gestation is associated with fewer VIP-producing neurons later in gestation compared to saline controls; therefore, alcohol-related changes in the number of VIP-expressing neurons may be responsible in part for the attenuated hypoxic cerebral vasodilation described in fetal and neonatal sheep exposed to alcohol earlier in gestation.

Binge alcohol exposure in the second trimester attenuates fetal cerebral blood flow response to hypoxia

Alcohol is detrimental to the developing brain and remains the leading cause of mental retardation in developed countries. The mechanism of alcohol brain damage remains elusive. Studies of neurological problems in adults have focused on alcohol's cerebrovascular effects, because alcoholism is a major risk factor for stroke and cerebrovascular injuries. However, few studies have examined similar cerebrovascular effects of fetal alcohol exposure. We examined the effect of chronic binge alcohol exposure during the second trimester on fetal cerebrovascular and metabolic responses to hypoxia in near-term sheep and tested the hypothesis that fetal alcohol exposure would attenuate cerebrovascular dilation to hypoxia. Pregnant ewes were infused with alcohol (1.5 g/kg) or saline intravenously at 60–90 days of gestation (full term = 150 days). At 125 days of gestation, we measured fetal cerebral blood flow (CBF) and oxygen metabolism at baseline and during hypoxia. Maternal blood alcohol averaged 214 ± 5.9 mg/dl immediately after the 1.5-h infusion, with similar values throughout the month of infusion. Hypoxia resulted in a robust increase in CBF in saline-infused fetuses. However, the CBF response to hypoxia in fetuses chronically exposed to alcohol was significantly attenuated. Cerebral oxygen delivery decreased in both groups of fetuses during hypoxia but to a greater degree in the alcohol-exposed fetuses. Prenatal alcohol exposure during the second trimester attenuates cerebrovascular responses to hypoxia in the third trimester. Altered cerebrovascular reactivity might be one mechanism for alcohol-related brain damage and might set the stage for further brain injury if a hypoxic insult occurs.

Hypoxic regulation of the fetal cerebral circulation

Fetal cerebrovascular responses to acute hypoxia are fundamentally different from those observed in the adult cerebral circulation. The magnitude of hypoxic vasodilatation in the fetal brain increases with postnatal age although fetal cerebrovascular responses to acute hypoxia can be complicated by age-dependent depressions of blood pressure and ventilation. Acute hypoxia promotes adenosine release, which depresses fetal cerebral oxygen consumption through action of adenosine on neuronal A1 receptors and vasodilatation through activation of A2 receptors on cerebral arteries. The vascular effect of adenosine can account for approximately half the vasodilatation observed in response to hypoxia. Hypoxia-induced release of nitric oxide and opioids can account for much of the adenosine-independent cerebral vasodilatation observed in response to hypoxia in the fetus. Direct effects of hypoxia on cerebral arteries account for the remaining fraction, although the vascular endothelium contributes relatively little to hypoxic vasodilatation in the immature cerebral circulation. In contrast to acute hypoxia, fetal cerebral blood flow tends to normalize during acclimatization to chronic hypoxia even though cardiac output is depressed. However, uncompensated chronic hypoxia in the fetus can produce significant changes in brain structure and function, alteration of respiratory drive and fluid balance, and increased incidence of intracranial hemorrhage and periventricular leukomalacia. At the level of the fetal cerebral arteries, chronic hypoxia increases protein content and depresses norepinephrine release, contractility, and receptor densities associated with contraction but also attenuates endothelial vasodilator capacity and decreases the ability of ATP-sensitive and calcium-sensitive potassium channels to promote vasorelaxation. Overall, fetal cerebrovascular adaptations to chronic hypoxia appear prioritized to conserve energy while preserving basic contractility. Many gaps remain in our understanding of how the effects of acute and chronic hypoxia are mediated in fetal cerebral arteries, but studies of adult cerebral arteries have produced many powerful pharmacological and molecular tools that are simply awaiting application in studies of fetal cerebral artery responses to hypoxia.

Chronic ethanol exposure during late gestation produces behavioral anomalies in neonatal lambs

A total of 45 pregnant ewes were assigned to one of three treatment groups: 1 g ethanol/kg maternal body weight (n = 18); pair-fed control (n = 15); and ad lib control (n = 12). Dosing started at gestational day (GD) 106, and was administered every other day until GD 134. Parturition occurred between GD 144 and 147. Analysis of the placentas indicated that ethanol exposure decreased cotyledon diameter and cotyledon weight compared to the control groups (p < 0. 05). At birth, lambs were given a Vigor Score and then behavior was assessed using a videotape monitoring system for 24 h. Offspring in the ethanol treatment group were significantly less vigorous at birth (p < 0.05). This finding reversed during the subsequent 24 h such that the ethanol-exposed lambs were significantly more active (p = 0.001) than the control lambs. Morphometric and histologic examination of the cerebral cortex and hippocampus revealed no differences amongst the three treatment groups. Collectively, the data demonstrate that moderate ethanol exposure during the third-trimester equivalent of gestation can produce placental dysmorphology and postnatal behavioral anomalies in neonatal lambs in the absence of gross neurologic injury.

Effects of alcohol on respiratory variables in normal humans

The study is designed to clarify the effect of low doses of alcohol on respiratory variables in air breathing normal subjects. Each subject was given an initial loading dose of alcohol (0.270 g/kg) followed, half an hour later, by a second dose (0.135 g/kg). Blood alcohol increased to a mean value of 52.0 +/- 3.0 (SEM) mg/100 ml at 1 hour. Resting ventilation increased significantly from a mean value of 6.25 +/- 0.41 litres min(-1) to 7.20 +/- 0.31 litres min(-1) 1 hour after alcohol (p= 0.025). Mean inspiratory flow was also increased (p= 0.045). End-tidal PCO² (PET CO²) showed a highly significant fall (1.87 +/- 0.35 mm Hg; p < 0.001) without a significant change in CO2 production rate (p > 0.05). PET CO² variability (100 x SD/mean) was low (mean 2.4%) and unaffected by alcohol. The longest end-expiratory pauses (apnoeas) observed for each subject were shortened significantly by alcohol (1.030 +/- 0.194 s and 0.690 +/- 0.138 s; p = 0.01). Moderate doses of alcohol in normal subjects, therefore lower PET CO² and shorten end-expiratory pauses (apnoeic periods) but do not affect PET CO² variability.