Vitamin A status after prophylactic intramuscular vitamin A supplementation in extremely low birth weight infants.

BACKGROUND: Vitamin A supplementation (VAS) is recommended to prevent bronchopulmonary dysplasia (BPD). Our objective was to evaluate the effect of VAS on vitamin A (VA) status. We hypothesized that VAS would improve VA status in extremely low birth weight (ELBW) infants. MATERIALS AND METHODS: Retrospective chart review of infants 1 year before and after initiation of VAS (5000 IU 3 times a week intramuscularly [IM]; total 12 doses). Linear regression was used to model impact of VAS on VA status (retinol level and retinol/retinol binding protein [RBP] ratio). Models were adjusted for time and generalized estimating equations were used to account for intraindividual correlation. RESULTS: Sixty-seven infants (mean gestational age 26 ± 2 weeks; mean body weight 803 ± 142 g) were included; 35 received VAS and 32 did not (no-VAS). Both groups had similar baseline characteristics. Infants who received VAS had mean retinol levels that were 9.0 mcg/dL (95% confidence interval [CI], 4.9-13.2; P < .001) higher and mean retinol/RBP ratios that were 0.21 (95% CI, 0.07-0.36; P = .005) higher than the no-VAS group. Retinol and retinol/RBP ratio increased with time (P < .001). Fewer infants in the VAS group had VA deficiency (retinol/RBP ratios <0.7) compared with the no-VAS group. Culture-positive sepsis was more common in the VAS group (48% vs 12%; P = .002). CONCLUSIONS: VA status in ELBW infants was improved and maintained over the first month of life with IM VAS. Because of concerns for potential risks of repeated injections, further studies are indicated to evaluate the optimal mode of VA delivery in preterm infants.

Adult responses to an ischemic stroke in a rat model of neonatal stress and morphine treatment.

Critically ill newborn infants experience stressors that may alter brain development. Using a rodent model, we previously showed that neonatal stress, morphine, and stress plus morphine treatments each influence early gene expression and may impair neurodevelopment and learning behavior. We hypothesized that the combination of neonatal stress with morphine may alter neonatal angiogenesis and/or adult cerebral blood vessel density and thus increase injury after cerebral ischemia in adulthood. To test this, neonatal Lewis rats underwent 8 h/d maternal separation, plus morning/afternoon hypoxia exposure and either saline or morphine treatment (2 mg/kg s.c.) from postnatal day 3-7. A subset received bromodeoxyuridine to track angiogenesis. Adult brains were stained with collagen IV to quantify cerebral blood vessel density. To examine vulnerability to brain injury, postnatal day 80 adult rats underwent right middle cerebral artery occlusion (MCAO) to produce unilateral ischemic lesions. Brains were removed and processed for histology 48 h after injury. Brain injury was assessed by histological evaluation of hematoxylin and eosin, and silver staining. In contrast to our hypothesis, neither neonatal morphine, stress, nor the combination affected cerebral vessel density or MCAO-induced brain injury. Neonatal angiogenesis was not detected in adult rats possibly due to turnover of endothelial cells. Although unrelated to angiogenesis, hippocampal granule cell neurogenesis was detected and there was a trend (P = 0.073) toward increased bromodeoxyuridine incorporation in rats that underwent neonatal stress. These findings are discussed in contrast to other data concerning the effects of morphine on cerebrovascular function, and acute effects of morphine on hippocampal neurogenesis.

Long-term effects of neonatal stress on adult conditioned place preference (CPP) and hippocampal neurogenesis.

Critically ill preterm infants are often exposed to stressors that may affect neurodevelopment and behavior. We reported that exposure of neonatal mice to stressors or morphine produced impairment of adult morphine-rewarded conditioned place preference (CPP) and altered hippocampal gene expression. We now further this line of inquiry by examining both short- and long-term effects of neonatal stress and morphine treatment. Neonatal C57BL/6 mice were treated twice daily from postnatal day (P) 5 to P9 using different combinations of factors. Subsets received saline or morphine injections (2mg/kgs.c.) or were exposed to our neonatal stress protocol (maternal separation 8h/d × 5d+gavage feedings ± hypoxia/hyperoxia). Short-term measures examined on P9 were neuronal fluorojade B and bromodeoxyuridine staining, along with urine corticosterone concentrations. Long-term measures examined in adult mice (>P60) included CPP learning to cocaine reward (± the kappa opioid receptor (KOR) agonist U50,488 injection), and adult hippocampal neurogenesis (PCNA immunolabeling). Neonatal stress (but not morphine) decreased the cocaine-CPP response and this effect was reversed by KOR stimulation. Both neonatal stress or morphine treatment increased hippocampal neurogenesis in adult mice. We conclude that reduced learning and increased hippocampal neurogenesis are both indicators that neonatal stress desensitized mice and reduced their arousal and stress responsiveness during adult CPP testing. Reconciled with other findings, these data collectively support the stress inoculation hypothesis whereby early life stressors prepare animals to tolerate future stress.

Rising prevalence of gastroschisis in Washington State.

The aim of this study was to assess gastroschisis prevalence in Washington (WA) State in relation to putative risk factors. Gastroschisis prevalence was calculated from the WA State birth cohort during 1987-2006 using an administrative database with birth certificate data linked with hospital discharge records and the ICD-9 procedure code 54.71, which specifies gastroschisis repair. Poisson regression analysis was used to evaluate time trends while adjusting for risk factors. Birth year was included as a linear term. Maternal age, smoking, race, residence in urban versus rural area, geographic region (eastern versus western Washington), paternal age, and infant gender were included as categorical factors. Prevalence ratios were adjusted for birth year and all of the preceding factors. Two hundred and eighty-two infants with gastroschisis were identified. In the adjusted analysis, the prevalence ratio for gastroschisis was 1.1 per year (95% CI 1.08-1.13), indicating an average 10% increase per birth year. Teen mothers were at a higher risk compared to mothers≥25 yr old (adjusted rate ratio [aRR] 8.02; 95% CI 5.30-12.13), as were teen fathers (aRR 2.35; 95% CI 1.48-3.74) compared to fathers≥25 years old. Maternal smoking was associated with a higher risk compared to those who were nonsmokers (aRR 1.58; 95% CI 1.19-2.09). Black mothers had a lower risk compared with white mothers. There was no association with geographic classification of mother's residence. Gastroschisis prevalence has increased in WA, particularly in teen mothers and in smokers. This is not explained by a rise in teenage pregnancies or maternal smoking. Further investigation of factors specific to teenage lifestyle is warranted.

Effects of neonatal stress and morphine on murine hippocampal gene expression.

Critically ill preterm infants experience multiple stressors while hospitalized. Morphine is commonly prescribed to ameliorate their pain and stress. We hypothesized that neonatal stress will have a dose-dependent effect on hippocampal gene expression, and these effects will be altered by morphine treatment. Male C57BL/6 mice were exposed to five treatment conditions between postnatal d 5 and 9: 1) control, 2) mild stress + saline, 3) mild stress + morphine, 4) severe stress + saline, and 5) severe stress + morphine. Hippocampal RNA was extracted and analyzed using Affymetrix Mouse Gene 1.0 ST Arrays. Single gene analysis and gene set analysis were used to compare groups with validation by qPCR. Stress resulted in enrichment of gene sets related to fear response, oxygen carrying capacity, and NMDA receptor synthesis. Morphine down-regulated gene sets related to immune function. Stress + morphine resulted in enrichment of mitochondrial electron transport gene sets and down-regulation of gene sets related to brain development and growth. We conclude that neonatal stress alone influences hippocampal gene expression, and morphine alters a subset of stress-related changes in gene expression and influences other gene sets. Stress + morphine show interaction effects not present with either stimulus alone. These changes may alter neurodevelopment.

Left ventricular hypertrophy is prevalent in Sprague-Dawley rats.

Unrecognized cardiovascular abnormalities may confound the interpretation of research data collected using rats. However, although SPF rat colonies are screened for microbes and kept under standardized environmental conditions, their cardiovascular status is largely unknown. We recently performed surgery on anesthetized 80-d-old Sprague-Dawley rats and observed a high mortality that could not be attributed to the procedures or preceding treatments. Upon necropsy, cardiomyopathy was readily apparent in a substantial proportion of these rats. To further evaluate the nature of this condition, we evaluated the histology and morphology of hearts from both Sprague-Dawley and Lewis rats. Compared with Lewis rats, Sprague-Dawley rats had greater left ventricular wall thickness and larger cardiomyocyte cell size. Severe left ventricle hypertrophy was present in 38% of young adult Sprague-Dawley rats. These findings may have implications for research models that use Sprague-Dawley rats.

Effects of neonatal stress and morphine on kappa opioid receptor signaling.

BACKGROUND: Critically ill neonates experience multiple stressors during hospitalization. Opioids are commonly prescribed to ameliorate their pain and stress. However, the enduring effects of stress and opioids are not understood. The kappa opioid system is important in the mediation of stress in adults, but little is known about its function in neonates. OBJECTIVES: To characterize kappa opioid receptor (KOR) distribution in the neonatal mouse brain and test whether neonatal exposure to morphine, stress, or both, change KOR signaling. METHODS: Five groups of wild-type C57BL/6 or prodynorphin (Pdyn) knockout mice were tested: (1) untreated control (dam-reared, no handling), (2) saline-injected control, (3) morphine-injected control, (4) stressed with saline injections and (5) stressed with morphine injections. Mice were treated from postnatal day 5 to postnatal day 9, after which their brains were immunolabeled with a phospho-specific KOR antibody (KOR-P), glial fibrillary acidic protein or glutamic acid decarboxylase. RESULTS: There were no effects of saline or morphine injection on KOR-P immunoreactivity. Neonatal stress increased KOR-P labeling in wild-type brains (p < 0.05), but not in Pdyn(-/-) animals. Mice exposed to stress and morphine showed region-specific increases in KOR-P immunoreactivity from 38 to 500% (p < 0.05 to p < 0.001), with marked gliosis. In stressed morphine-treated Pdyn(-/-) animals, KOR-P immunoreactivity was absent, but gliosis increased compared to wild-type animals. CONCLUSIONS: Neonatal stress increases KOR activation via the dynorphin system. Neonatal stress plus morphine treatment further increased this response and also resulted in hippocampal gliosis. Enhanced gliosis noted in Pdyn(-/-) animals suggests that the endogenous dynorphin may play a role in downregulating this inflammatory response.

Neonatal stress or morphine treatment alters adult mouse conditioned place preference.

BACKGROUND: Hospitalized preterm infants may experience pain and stress, and narcotics are often administered to lessen their suffering. However, prolonged narcotic therapy may be detrimental during neonatal brain development. Using a rat model combining neonatal stress and morphine, we found that neonatal morphine impaired adult learning. Here we describe a new mouse model examining lasting effects of neonatal stress and morphine. OBJECTIVE: We tested whether repeated neonatal stress and/or morphine exposure affects early neurodevelopmental or adult behaviors. METHODS: Five groups of C57/BL6 mice (1: untreated; 2: morphine (2 mg/kg s.c., b.i.d.); 3: saline, 4: stress + morphine; 5: stress + saline) were treated from postnatal day (P) 5 to P9. Stress consisted of daily maternal separation/isolation (08:00-15:00 h) with gavage feedings and twice daily exposure to brief hypoxia/hyperoxia. Developmental behaviors included righting (P5) and negative geotaxis (P9). Adult behaviors included elevated plus maze, morphine place-preference conditioning, and forced-swimming. Plasma concentrations of morphine (P7) and corticosterone (P9 and adult) were measured. RESULTS: Neonatal stress or neonatal morphine alone impaired adult place-preference conditioning, but the combination did not (interaction p < 0.01). Adult basal corticosterones were reduced by neonatal morphine treatment. There were no substantial differences in elevated plus maze or forced-swimming times. CONCLUSIONS: Neonatal stress and morphine treatment produced long-lasting behavioral and hormonal effects which suggest that neonatal morphine reduces adult arousal and neonatal stress exaggerates adult arousal, each to a degree sufficient to alter learning, while the combined impact of these neonatal treatments does not alter adult learning.

A phase I/II trial of high-dose erythropoietin in extremely low birth weight infants: pharmacokinetics and safety.

OBJECTIVES: High-dose recombinant erythropoietin is neuroprotective in animal models of neonatal brain injury. Extremely low birth weight infants are at high risk for brain injury and neurodevelopmental problems and might benefit from recombinant erythropoietin. We designed a phase I/II trial to test the safety and determine the pharmacokinetics of high-dose recombinant erythropoietin in extremely low birth weight infants. METHODS: In a prospective, dose-escalation, open-label trial, we compared 30 infants who were treated with high-dose recombinant erythropoietin with 30 concurrent control subjects. Eligible infants were <24 hours old,

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.

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.

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.

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.

Dopamine does not limit fetal cerebrovascular responses to hypoxia.

Dopamine is used clinically to stabilize mean arterial blood pressure (MAP) in sick infants. One goal of this therapeutic intervention is to maintain adequate cerebral blood flow (CBF) and perfusion pressure. High-dose intravenous dopamine has been previously demonstrated to increase cerebrovascular resistance (CVR) in near-term fetal sheep. We hypothesized that this vascular response might limit cerebral vasodilatation during acute isocapnic hypoxia. We studied nine near-term chronically catheterized unanesthetized fetal sheep. Using radiolabeled microspheres to measure fetal CBF, we calculated CVR at baseline, during fetal hypoxia, and then with the addition of an intravenous dopamine infusion at 2.5, 7.5, and 25 microg.kg(-1).min(-1) while hypoxia continued. During acute isocapnic fetal hypoxia, CBF increased 73.0 +/- 14.1% and CVR decreased 38.9 +/- 4.9% from baseline. Dopamine infusion at 2.5 and 7.5 microg.kg(-1).min(-1), begun during hypoxia, did not alter CVR or MAP, but MAP increased when dopamine infusion was increased to 25 microg.kg(-1).min(-1). Dopamine did not alter CBF or affect the CBF response to hypoxia at any dose. However, CVR increased at a dopamine infusion rate of 25 microg.kg(-1).min(-1). This increase in CVR at the highest dopamine infusion rate is likely an autoregulatory response to the increase in MAP, similar to our previous findings. Therefore, in chronically catheterized unanesthetized near-term fetal sheep, dopamine does not alter the expected cerebrovascular responses to hypoxia.

Effects of first trimester binge alcohol exposure on developing white matter in fetal sheep.

Heavy prenatal alcohol exposure is associated with neurodevelopmental abnormalities. Neuropathologic and neuroimaging studies have shown a wide range of structural problems, including abnormal neuronal migration and volume reduction in specific brain regions, including white matter. We identified foci of significant fetal white matter microglia-macrophage immunoreactivity in a "binge" model of early prenatal alcohol exposure in sheep. Ewes of alcohol-exposed fetuses received daily 90 min alcohol (1.5 gm/kg i.v.) infusions at 30-60 d gestation (term = 147 d). Ewes of control fetuses received same volume infusions of normal saline intravenously. Near-term (125 d gestation) fetal brains were labeled with microglia-macrophages using HAM56 antibody. We quantified dense immunoreactive cellular regions across sections and anatomical locations using computer-assisted microscopy and quantitative morphometry. The proportional HAM56-positive area in cortical white matter was greater in the alcohol-exposed fetuses (1.6%) compared with the saline controls (0.7%). The areas were localized to the frontal gyral white matter, temporal gyral white matter, optic radiation, and others (corpus callosum, septum pellucidum, fasciculus subcallosus, and external capsule), with a greater distribution in the gyral white matter. The greater area of macrophage-rich regions in near-term fetal sheep brain suggests a vulnerability of developing white matter that is enhanced by early alcohol exposure.

Preliminary evidence that prenatal alcohol damage may be visible in averaged ultrasound images of the neonatal human corpus callosum.

Brain damage consequent to prenatal alcohol exposure can be detected by measurements of the corpus callosum in the midline magnetic resonance (MR) brain image in adolescents and adults. The present article extends this finding into the neonatal period, when the power of detection to ameliorate the quality of the child's future life is greatest. The midline corpus callosum of the very young infant can be located reliably in multiple frames of clinical transfontanelle ultrasound. We studied a sample of 18 children aged 17 weeks or less, 7 of whom were exposed to high levels of alcohol prenatally and 11 of whom were not exposed or only minimally exposed. The midline callosum of each child was imaged up to 50 times by a standard clinical device, and coplanar subsets of these series were averaged with reference to fiducial image structures. On each average image four semilandmark points were set and their configuration quantified by standard landmark methods. The angle between the terminal bulb of splenium and the long axis of the callosal outline classifies four of the seven exposed infants as different from all 11 of the unexposed infants. This simple angle measurement upon averaged ultrasound images of the human neonatal midline corpus callosum, perhaps a version of the long-sought "biomarker of prenatal alcohol damage," may be able to discriminate baby brains affected by prenatal alcohol exposure from those that were unaffected.

Cerebrovascular effects of rapid volume expansion in preterm fetal sheep.

Preterm human infants are often treated with volume expansion during their initial stabilization. There are limited data regarding the cerebral vascular effects of this therapeutic approach. The effects of blood volume expansion on cerebral vascular reactivity and oxygen metabolism in very immature animals have not been determined. We examined the effects of volume expansion, with and without hypoxia, on cerebral blood flow and metabolism in unanesthetized, chronically catheterized, preterm fetal sheep. Rapid volume expansion with i.v. dextran increased circulating blood volume. Arterial blood pressure did not increase, nor did cerebral blood flow. However, volume expansion resulted in lower arterial Hb concentration and, consequently, oxygen content without a compensatory increase in cerebral blood flow. Cerebral oxygen delivery fell significantly. Induction of severe hypoxia after volume expansion resulted in an increase in cerebral blood flow, as expected, but the increase in flow was not enough to maintain cerebral oxygen delivery. Rapid volume expansion in normovolemic preterm fetal sheep is associated with decreased cerebral oxygen delivery, and this is further compromised when oxygen content is decreased.

Erytropoietin concentrations in cerebrospinal fluid of nonhuman primates and fetal sheep following high-dose recombinant erythropoietin.

Erythropoietin (Epo) decreases neuronal injury and cell death in vitro and in vivo. To lay the groundwork for use of Epo as a potential therapy for brain injury, we tested the hypothesis that systemic dosing of high-dose recombinant Epo (rEpo) would result in neuroprotective rEpo concentrations in the spinal fluid of adult and developing animals. This report characterizes the pharmacokinetics of high-dose rEpo in the blood and spinal fluid of juvenile and adult nonhuman primates (n = 7) and fetal sheep (n = 37) following a single injection. Timed blood and spinal fluid samples were collected following rEpo injection. Epo accumulation in spinal fluid was dependent on peak serum concentration and time following injection. We demonstrate that high-dose rEpo was well tolerated and results in neuroprotective concentrations in spinal fluid of adult and developing animal models by 2-2.5 h after injection.

Cerebrovascular effects of intravenous dopamine infusions in fetal sheep.

Preterm infants are often treated with intravenous dopamine to increase mean arterial blood pressure (MAP). However, there are few data regarding cerebrovascular responses of developing animals to dopamine infusions. We studied eight near-term and eight preterm chronically catheterized unanesthetized fetal sheep. We measured cerebral blood flow and calculated cerebral vascular resistance (CVR) at baseline and during dopamine infusion at 2.5, 7.5, 25, and 75 microg x kg(-1) x min(-1). In preterm fetuses, MAP increased only at 75 microg x kg(-1) x min(-1) (25 +/- 5%), whereas in near-term fetuses MAP increased at 25 microg x kg(-1) x min(-1) (28 +/- 4%) and further at 75 microg x kg(-1) x min(-1) (51 +/- 3%). Dopamine infusion was associated with cerebral vasoconstriction in both groups. At 25 microg x kg(-1) x min(-1), CVR increased 77 +/- 51% in preterm fetuses and 41 +/- 11% in near-term fetuses, and at 75 microg x kg(-1) x min(-1), CVR increased 80 +/- 33% in preterm fetuses and 83 +/- 21% in near-term fetuses. We tested these responses to dopamine in 11 additional near-term fetuses under alpha-adrenergic blockade (phenoxybenzamine, n = 5) and under dopaminergic D(1)-receptor blockade (SCH-23390, n = 6). Phenoxybenzamine completely blocked dopamine's pressor and cerebral vasoconstrictive effects, while D(1)-receptor blockade had no effect. Therefore, in unanesthetized developing fetuses, dopamine infusion is associated with cerebral vasoconstriction, which is likely an autoregulatory, alpha-adrenergic response to an increase in blood pressure.