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Background: Creatine kinase MB (CK-MB), which exists mainly in the cytoplasm of myocardial cells, is currently accepted as an indicator and has high sensitivity and specificity for the diagnosis of myocardial injury. Objective: This study was aimed to estimate serum creatine kinase MB (CK-MB) levels after asphyxia-induced myocardial injury in neonates. Patients and methods: 40 neonates were included in this study and divided into 20 cases with the diagnosis of perinatal hypoxia ischemia and 20 controls admitted to Neonatology Unit of Pediatric Department at Zagazig University. Serum CK-MB levels were estimated in all studied neonates. Results: In the present study serum CK-MB levels in cases were significantly higher than controls. A significant area under curve with cutoff >14.5 (units /L) with sensitivity 99%and specificity 97.5% for CK-MB. Encephalopathy cases were significantly associated with higher HR and CKMB. Cases with organ failure were significantly associated with higher HR and CKMB. Cases with metabolic acidosis were significantly associated with higher HR and CKMB. Conclusion: It could be concluded that cases with hypoxic ischemic encephalopathy (HIE) and those with multiple organ failure had a more pronounced elevation of serum CK-MB compared with cases of hypoxia-ischemia with no organ failure. Similarly, patients with HIE had significant elevation of cardiac enzymes. Collectively, these findings indicate more myocardial systolic dysfunction and damage in neonates with HIE and organ failure.

Objective: Herein, we aimed to investigate the long-term effects of neonatal hypoxia and the potential protective role of melatonin and memantine on the learning and memory. Methods: Seven-day-old rat underwent right carotid ligation, followed by hypoxia. Rat received Melatonin (MLT) (4 mg/kg), Memantine (MEM) (20 mg/kg), and MLT+MEM combination after hypoxia. We tested these rats for anxiety by elevated O-maze and for spatial learning and memory by Morris water maze (MWM) at postnatal day 45. Results: Hypoxia increased the level of anxiety compared to the control group (p=0.05) while treatment of MLT, MEM, and MLT+MEM ameliorated this effect. In addition, hypoxia produced significant decrease in spatial learning of the rats on the fourth day of training (P=0.05) and the percent time spent in the platform quadrant and the entrance frequencies to the platform quadrant compared to the control group (P=0.049 and P=0.023). Treatment of MLT, MEM, and MLT+MEM after hypoxia improved the performance of the rats at the third (P=0.686, P=0.876, P=0.977, respectively) and fourth day (P=0.738, P=0.553, P=0.789, respectively) of MWM training. The decrease in the percent time spent was ameliorated by the treatment of MLT (P=0.239), MEM (P=0.289), and MLT+MEM (P=0.567) compared to the control group. In addition, MLT treatment significantly increased the entrance frequency to the platform quadrant compared to the hypoxia group (P=0.020). Conclusion: Our data suggested that the MLT was more effective in the release of memory deficits from hypoxia-related damage. MLT might have a therapeutic value in improving hypoxic damage in the developing brain. WOS:000640976900004

Perinatal hypoxia ischemia (HI) is a significant cause of brain injury in surviving infants. Although hypothermia improves outcomes in some infants, additional therapies are needed since about 40% of infants still have a poor outcome. Acetyl-L-carnitine (ALCAR), an acetylated derivative of L-carnitine, protected against early changes in brain metabolites and mitochondrial function after HI on postnatal day (PND) 7 in a rat pup model of near-term HI injury. However, its efficacy in long-term structural and functional outcomes remains unexplored. We determined the efficacy of ALCAR therapy administered to rat pups after HI at PND 7, using both longitudinal in vivo magnetic resonance imaging and behavioral tests, in male and female rats. HI led to sex-specific behavioral impairment, with males exhibiting more global functional deficits than females. Interestingly, HI reduced the volume of the contralateral hemisphere in males only, suggesting that the brain injury is more diffuse in males than in females. Treatment with ALCAR improved both morphological and functional outcomes in both male and female rats. These results suggest that ALCAR may be a potential therapy for clinical use since the treatment attenuated the moderate injury produced under the experimental conditions used and improved the functional outcome in preclinical studies.

Neonatal asphyxia occurs due to reduction in oxygen supply to vital organs in the newborn. Rapid restoration of oxygen to the lungs after a long period of asphyxia can cause lung injury and decline of respiratory function, which result from the activity of molecules that induce vascular changes in the lung such as nitric oxide (NO) and vascular endothelial growth factors (VEGF). In this study, we evaluated the pulmonary and vascular morphometry of rats submitted to the model of neonatal asphyxia and mechanical ventilation, their expression of pulmonary VEGF, VEGF receptors (VEGFR-1/VEGFR-2), and endothelial NO synthase (eNOS). Neonate Sprague-Dawley rats (CEUA #043/2011) were divided into four groups (n=8 each): control (C), control submitted to ventilation (CV), hypoxia (H), and hypoxia submitted to ventilation (HV). The fetuses were harvested at 21.5 days of gestation. The morphometric variables measured were body weight (BW), total lung weight (TLW), left lung weight (LLW), and TLW/BW ratio. Pulmonary vascular measurements, VEGFR-1, VEGFR-2, VEGF, and eNOS immunohistochemistry were performed. The morphometric analysis showed decreased TLW and TLW/BW ratio in HV compared to C and H (P

While extensive studies report that neonatal hypoxia-ischemia (HI) induces long-term cognitive impairment via inflammatory responses in the brain, little is known about the role of early peripheral inflammation response in HI injury. Here we used a neonatal hypoxia rodent model by subjecting postnatal day 0 (P0d) rat pups to systemic hypoxia (3.5 h), a condition that is commonly seen in clinic neonates, Then, an initial dose of minocycline (45 mg/kg) was injected intraperitoneally (i.p.) 2 h after the hypoxia exposure ended, followed by half dosage (22.5 mg/kg) minocycline treatment for next 6 consecutive days daily. Saline was injected as vehicle control. To examine how early peripheral inflammation responded to hypoxia and whether this peripheral inflammation response was associated to cognitive deficits. We found that neonatal hypoxia significantly increased leukocytes not only in blood, but also increased the monocytes in central nervous system (CNS), indicated by presence of C-C chemokine receptor type 2 (CCR2+)/CD11b+CD45+ positive cells and CCR2 protein expression level. The early onset of peripheral inflammation response was followed by a late onset of brain inflammation that was demonstrated by level of cytokine IL-1β and ionized calcium binding adapter molecule 1(Iba-1; activated microglial cell marker). Interrupted blood-brain barrier (BBB), hypomyelination and learning and memory deficits were seen after hypoxia. Interestingly, the cognitive function was highly correlated with hypoxia-induced leukocyte response. Notably, administration of minocycline even after the onset of hypoxia significantly suppressed leukocyte-mediated inflammation as well as brain inflammation, demonstrating neuroprotection in systemic hypoxia-induced brain damage. Our data provided new insights that systemic hypoxia induces cognitive dysfunction, which involves the leukocyte-mediated peripheral inflammation response.

Hypoxia-ischemia (HI) is a model of cerebral ischemia used to model neonatal hypoxia and to study brain damage. Interpreting the results of experiments that use HI rests partly on the assumption that only the brain suffers major damage. In this study, we demonstrate that HI also has adverse consequences on the heart. Both infarction scoring and measurements of troponin I indicate cardiac damage subsequent to HI. These results indicate that the effects of HI on the heart may confound the interpretation of experiments that have used HI to study neuroprotection or other aspects of brain damage.

Neonatal hypoxia-ischemia (HI) affects 60% of low birth weight infants and up to 40% of preterm births. Cell death and brain injury after HI have been shown to cause long-lasting behavioral deficits. By using a battery of behavioral tests on second generation 3-week-old rodents, we found that neonatal HI is associated with behavioral outcomes in the progeny of HI-affected parents. Our results suggest an epigenetic transfer mechanism of some of the neurological symptoms associated with neonatal HI. Elucidating the transfer of brain injury to the next generation after HI calls attention to the risks associated with HI injury and the need for proper treatment to reverse these effects. Assessing the devastating extent of HI's reach serves as a cautionary tale to the risks associated with neonatal HI, and provides an incentive to create improved therapeutic measures to treat HI.

Acute hypoxia at postnatal day (P) 10 is an accepted model of human neonatal hypoxia which results, among other consequences, in increased hippocampal excitability. Hypoxic–ischemic injury, which mimics stroke, has been shown to result in changes in connexins (Cxs), however, changes in Cxs have not been studied in the P10 hypoxia model. The aim of this study was to investigate changes in the hippocampal expression of three different connexins at consecutive developmental stages after acute hypoxia at P10 (10 min and 30 min after reoxygenation, P11, P14, P17, P29, and P45) as compared to sham manipulated pups. After acute hypoxia at P10, Cx30 protein levels were increased at 30 min after reoxygenation, at P11 and at P14, and then returned to control levels. Cx36 protein levels transiently decreased at P11 after acute hypoxia then returned to control levels. Cx43 protein levels did not change at any of the time points. Although changes in mRNA expression were observed during development for Cx30 only, acute hypoxia did not result in changes in mRNA expression of all these Cxs when compared to age matched controls suggesting that acute hypoxia induced posttranslational changes in protein expression.

WOS:000346149200005 PubMed: 25491683 Background. Neonatal hypoxic-ischemic (HI) injury has been considered to have acute and long term deleterious effects on many tissues, including the peripheral nerve. Objectives. In this study, the effects of a tumor necrosis factor-alpha (TNF-alpha) inhibitor (etanercept) on peripheral nerve damage and the ultrastructure of the sciatic nerve and gastrocnemius muscle in rats exposed to HI during the neonatal period were examined. Material and Methods. In this study, 45 seven-day-old rats were used and they were divided into three groups. The right carotid arteries of the rats in the saline and etanercept groups were ligated and put in a hypoxia chamber containing 8% oxygen for two hours. Just after hypoxia, the etanercept group was given 10 mg/kg etanercept, but the saline group had only saline intraperitoneally. The sham group rats' carotid arteries were not ligated or put in hypoxia. The amplitude, area and latency of sciatic nerve compound motor action potential (CMAP), which mainly reflects axonopathy and myelinopathy, were measured using standard techniques in the seventeenth week following the HI. Sciatic nerve and gastrocnemius muscle were evaluated with a transmission electron microscope, and grading for myelin sheath damage was done to all groups. Results. Neuropathy was seen in rats after HI. While treatment with etanercept showed a protective effect for the axons of sciatic nerve, demyelination could not be recovered with etanercept. Conclusions. This study is the first in literature to show a partial interruption of the signal through the peripheral nerve fibers caused by axonal and myelin dysfunction continuation in rats exposed to HI after birth, in the 17th week

Unlike in the adult, the perinatal/neonatal pulmonary vascular response to chronic hypoxic exposure is much more rapid and severe and results in the failure of the fetal/neonatal circulation to adapt to a response supporting postnatal life. This, in turn, contributes to the pathogenesis of persistent pulmonary hypertension of the newborn and pulmonary vascular dysfunction later in life. As such, furthering our understanding of the mechanisms and pathology of perinatal/neonatal pulmonary hypertension development leading to adult diseases is important to support more effective therapeutic target identification.

Neonatal hypoxia increases aldosterone production and plasma lipids. Because fatty acids can inhibit aldosterone synthesis, we hypothesized that increases in plasma lipids restrain aldosteronogenesis in the hypoxic neonate. We exposed rats to 7 days of hypoxia from birth to 7 days of age (suckling) or from 28 to 35 days of age (weaned at day 21). Plasma was analyzed for lipid content, and steroidogenesis was studied in dispersed whole adrenal glands untreated and treated to wash away lipids. Hypoxia increased plasma cholesterol, triglycerides, and nonesterified fatty acids in the suckling neonatal rat only. Washing away lipids increased aldosterone production in cells from 7-day-old rats exposed to hypoxia, but not in cells from normoxic 7-day-old rats or from normoxic or hypoxic 35-day-old rats. Addition of oleic or linolenic acid to washed cells inhibited both aldosterone and corticosterone production, although cells from hypoxic 7-day-old rats were less sensitive. We conclude that hypoxia induces hyperlipidemia in the suckling neonate and that elevated nonesterified fatty acids inhibit aldosteronogenesis.

BACKGROUND The aim of this study is to determine carnitine levels in hypoxic-ischemiac neonates. METHODS Total and free carnitine levels were measured in 20 normal term neonates and 20 term neonates who were diagnosed as hypoxia-ischemia. RESULTS Both total carnitine levels (43.7 +/- 10.0 microg/dl vice 27.8 +/- 11.8 microg/dl, p

We investigated whether the effect of neonatal hypoxia on amphetamine-induced hyperlocomotion can reproduce the ontogenic (age of onset) properties of schizophrenia. Neonatal hypoxia enhanced amphetamine-induced hyperlocomotion in adult mice and decreased it in adolescent mice. These findings provide ontogenic validity for this very simple animal model of schizophrenia.

Hypoxia-ischemia (HI; concurrent oxygen/blood deficiency) and associated encephalopathy represent a common cause of neurological injury in premature/low-birth-weight infants and term infants with birth complications. Resulting behavioral impairments include cognitive and/or sensory processing deficits, as well as language disabilities, and clinical evidence shows that male infants with HI exhibit more severe cognitive deficits compared to females with equivalent injury. Evidence also demonstrates activation of sex-dependent apoptotic pathways following HI events, with males preferentially activating a caspase-independent cascade of cell death and females preferentially activating a caspase-dependent cascade following neonatal hypoxic and/or ischemic insults. Based on these combined data, the ‘female protection’ following HI injury may reflect the endogenous X-linked inhibitor of apoptosis (XIAP), which effectively binds effector caspases and halts downstream cleavage of effector caspases (thus reducing cell death). To test this theory, the current study utilized neonatal injections of vehicle or embelin (a small molecule inhibitor of XIAP) in male and female rats with or without induced HI injury on postnatal day 7 (P7). Subsequent behavioral testing using a clinically relevant task revealed that the inhibition of XIAP exacerbated HI-induced persistent behavioral deficits in females, with no effect on HI males. These results support sex differences in mechanisms of cell death following early HI injuries, and suggest a potential clinical benefit from the development of sex-specific neuroprotectants for the treatment of HI.

INTRODUCTION: As a consequence of obstetric complications hypoxia has been discussed as a possible factor in the pathophysiology of schizophrenia. The present study investigated the effects of weak chronic neonatal hypoxia in rats on different behavioural animal models of schizophrenia. METHODS: (1) After neonatal hypoxia, half of the pups were fostered by normally treated nurse animals to control for possible maternal effects. (2) The animals were tested on postnatal days (PD) 36, 86, 120 and 150 by applying three different behavioural tests: prepulse inhibition (PPI), social interaction and recognition, and motor activity in an open field. (3) Before the PD 150 test, half of the animals had been chronically treated with the antipsychotic drug clozapine (45 mg/kg/day). RESULTS: Rats exposed to hypoxia as neonates exhibited a deficit in locomotor activity on PD 86, 120, and 150, as well as a PPI deficit on PD 120 and 150 but not before. Chronic treatment with clozapine reverses the hypoxia induced PPI deficit, but not the decreased locomotor activity. In a second experiment, clozapine was chronically administered before PD 120 and blocked the development of the PPI deficit in the animals exposed to hypoxia. DISCUSSION: The time course of the hypoxia-induced PPI deficit and reversibility by clozapine supports the validity of our animal model and the hypothesis that hypoxia as an obstetric complication is an important factor in the pathophysiology of schizophrenia.

We have previously shown that neonatal mice deficient in endothelial nitric oxide synthase (eNOS−/−) are more susceptible to hypoxic inhibition of alveolar and vascular growth. Although eNOS is downregulated, the role of nitric oxide (NO) during recovery after neonatal lung injury is poorly understood. We hypothesized that lung vascular and alveolar growth would remain impaired in eNOS−/− mice during recovery in room air and that NO therapy would augment compensatory lung growth in the eNOS−/− mice during recovery. Mice (1 day old) from heterozygous (eNOS+/−) parents were placed in hypobaric hypoxia (FiO2= 0.16). After 10 days, pups were to recovered in room air (HR group) or inhaled NO (10 parts/million; HiNO group) until 3 wk of age, when lung tissue was collected. Morphometric analysis revealed that the eNOS−/− mice in the HR group had persistently abnormal lung structure compared with eNOS-sufficient (eNOS+/+) mice (increased mean linear intercept and reduced radial alveolar counts, nodal point density, and vessel density). Lung morphology of the eNOS+/− was not different from eNOS+/+. Inhaled NO after neonatal hypoxia stimulated compensatory lung growth in eNOS−/− mice that completely restored normal lung structure. eNOS+/− mice (HR group) had a 2.5-fold increase in lung vascular endothelial growth factor (VEGFR)-2 protein compared with eNOS+/+ ( P < 0.05). eNOS−/− mice (HiNO group) had a 66% increase in lung VEGFR-2 protein compared with eNOS−/− (HR group; P < 0.01). We conclude that deficiency of eNOS leads to a persistent failure of lung growth during recovery from neonatal hypoxia and that, after hypoxia, inhaled NO stimulates alveolar and vascular growth in eNOS−/− mice.

Increases in plasma lipids occur during hypoxia in suckling but not in weaned rats and may result from altered hepatic enzyme activity. We exposed rats to 7 days of hypoxia from birth to 7 days of age (suckling) or from 28 to 35 days of age (weaned at day 21). Hypoxia led to an increase in hepatic lipid content in the suckling rat only. Hepatic lipase was decreased to approximately 45% of control in 7-day-old rats exposed to hypoxia but not in hypoxic 35-day-old rats. Hypoxic suckling rats also had a 50% reduction in lactate dehydrogenase activity, whereas transaminase activity and CYP1A and CYP3A protein content were not different between hypoxic and normoxic groups. Additional rats were studied 7 and 14 days after recovery from hypoxic exposure from birth to 7 days of age; hepatic lipase activity had recovered to 85% by 7 days and to 100% by 14 days in the rats previously exposed to hypoxia. Administration of dexamethasone to neonatal rats to simulate the hyperglucocorticoid state found in hypoxic 7-day-old rats led to a moderate decrease ( approximately 75% of control) in hepatic lipases. Developmentally, in the normoxic state, hepatic lipases increased rapidly after birth and reached levels more than twofold that of the newborn by 7 days of age. Hypoxia delays the maturation of hepatic lipases. We suggest that the decrease in hepatic lipase activity contributes to hyperlipemia in the hypoxic newborn rats.

Background- Hypoxia during the first week of life can induce neuronal death in vulnerable brain regions usually associated with an impairment of cognitive function that can be detected later in life. The neurobiological changes mediated through neurotransmitters and other signaling molecules associated with neonatal hypoxia are an important aspect in establishing a proper neonatal care. Methods- The present study evaluated total GABA, GABAB receptor alterations, gene expression changes in GABAB receptor and glutamate decarboxylase in the cerebellum and brain stem of hypoxic neonatal rats and the resuscitation groups with glucose, oxygen and epinephrine. Radiolabelled GABA and baclofen were used for receptor studies of GABA and GABAB receptors respectively and Real Time PCR analysis using specific probes for GABAB receptor and GAD mRNA was done for gene expression studies. Results- The adaptive response of the body to hypoxic stress resulted in a reduction in total GABA and GABAB receptors along with decreased GABAB receptor and GAD gene expression in the cerebellum and brain stem. Hypoxic rats supplemented with glucose alone and with oxygen showed a reversal of the receptor alterations and changes in GAD. Resuscitation with oxygen alone and epinephrine was less effective in reversing the receptor alterations. Conclusions- Being a source of immediate energy, glucose can reduce the ATP-depletion-induced changes in GABA and oxygenation, which helps in encountering hypoxia. The present study suggests that reduction in the GABAB receptors functional regulation during hypoxia plays an important role in central nervous system damage. Resuscitation with glucose alone and glucose and oxygen to hypoxic neonatal rats helps in protecting the brain from severe hypoxic damage.

Mild/Moderate Neonatal Hypoxia(MMNH) with Normal Blood Glucose Levels(BGL) Influence in Rats Maze Performance(MP). 49

Noradrenergic (NA) neurons in the brainstem are assumed to be involved in arousal mechanisms (locus coeruleus or A6) and cardio-respiratory control(nucl. tr. solitarius or A2). We have earlier reported an acute depression of NA turnover in newborn rats exposed to hypoxia (Acta Physiol.Scand.1992.144:433) The aim was now to investigate the acute effect of perinatal asphyxia and the long-term effects of chronic hypoxia on NA-turnover in the rat brain.

DEXTROMETHORPHAN (DM) AMELIORATES EFFECTS OF NEONATAL HYPOXIA ON BRAIN MORPHOLOGY AND SEIZURE THRESHOLD IN RATS. • 2239

Fetal and/or neonatal malnutrition has been reported to cause lifelong changes of the control of blood pressure and glucose control etc. according to Barker et al (Lancet 341:938-941.1993). The aim of the present study was to investigate whether chronic neonatal hypoxia could cause longterm changes of catecholamine (CA) turnover in the sympatho-adrenal system and the carotid bodies One day old male pups were exposed with their dams to mild hypoxia (10% O2) for 6 days and thereafter grew up under normoxia until sacrifice. Normoxic control and neonatal hypoxic rats were examined at 3 or 8 weeks with regard to CA turnover. The levels and turnover rates of dopamine (DA), norepinephrine(NE) were determined in sympathetic ganglia and their main target organs, the adrenals and the carotid bodies. After exposure to neonatal hypoxia the turnover rates of NE in the superior cervical, stellate and coeliac-mesenteric ganglia were significantly (p

AIM:We studied the effect of moderate hypoxia on nuclei/cytoplasm index at different levels of the parietal cortex of the rat at 1 month of age. MATERIAL AND METHODS: Eight brains coming from 2 litters of 1 month-old rats submitted to a neonatal hypoxia (Fi O2=10%) and standardized to 10 animals per litter were processed and stained with Nissl method. Random slide of each case was selected and studied by digitalized microscopic pictures of 70 μm width and all the cortical structures depth. Measurements of main nuclei and cytoplasm diameters of neurons in different layers were taken and results compared with 6 controls brought up in the same circumstances. Mann-Whitney test was used to comparisons. CONCLUSIONS: Nuclei/cytoplasm index of pyramidal cells was significantly greater among hypoxic than in control animals. We can conclude that slight hypoxic expositions can produce alterations in the rat neurons morphology in later stages of the development.

As a consequence of obstetric complications, neonatal hypoxia has been discussed as an environmental factor in the pathophysiology of schizophrenia. However, the biological consequences of hypoxia are unclear. The neurodevelopmental hypothesis of schizophrenia suggests that the onset of abnormal brain development and neuropathology occurs perinatally, whereas symptoms of the disease appear in early adulthood. In our animal model of chronic neonatal hypoxia, we have detected behavioral alterations resembling those known from schizophrenia. Disturbances in cell proliferation possibly contribute to the pathophysiology of this disease. In the present study, we used postnatal rats to investigate cell proliferation in several brain areas following neonatal hypoxia. Rats were repeatedly exposed to hypoxia (89 % N(2), 11 % O(2)) from postnatal day (PD) 4-8. We then evaluated cell proliferation on PD 13 and 39, respectively. These investigations were performed in the anterior cingulate cortex (ACC), caudate-putamen (CPU), dentate gyrus, and subventricular zone. Rats exposed to hypoxia exhibited increased cell proliferation in the ACC at PD 13, normalizing at PD 39. In other brain regions, no alterations have been detected. Additionally, hypoxia-treated rats showed decreased CPU volume at PD 13. The results of the present study on the one hand support the assumption of chronic hypoxia influencing transient cell proliferation in the ACC, and on the other hand reveal normalization during ageing.

Previous studies have shown that severe neonatal asphyxia and hypoxia lead to a redistribution of cerebral blood flow (CBF) with a preferential perfusion of the brain stem. The present study shows that this mechanism is operative also in moderately hypoxic newborn lambs (oxygen saturation 32.7-65.2) with a threshold of about 25% reduction in oxygen saturation. In hypoxia, the mean increase in total CBF, brain stem and telencephalic blood flow was 44%, 68% and 43%, respectively (five lambs). We found that naloxone reverses this redistribution, and that the effects of naloxone on telencephalic perfusion and cerebral metabolic rate of oxygen (CMRO2) were proportional. In hypoxia + naloxone (1 mg/kg), a further increase in total CBF, brain stem, and telencephalic blood flow of 30%, 7% and 31% was noted. We therefore suggest that the redistribution of CBF is an important opioid-mediated homeostatic mechanism, which diminishes the metabolic requirements of the newer part of the brain in hypoxia and allows a preferential perfusion of the vital structures of the brain stem.

Sinusoidal heart rate traces were detected in 8 patients, 6 of whom died; the 2 survivors showed evidence of gross cerebral damage. It is felt that the origin of the sinusoidal curve is probably central and reflects loss of central control of heart rate.

Hypoxia in the neonate releases catecholamines from the adrenal medulla, a response which is necessary to survive. This study examines whether a similar dependence exists for the ability of brain and heart tissue to recover from hypoxia-induced damage, as assessed by measurements of ornithine decarboxylase (ODC) activity. Hypoxia at either 1 day or 8 days of age produced a subsequent elevation of brain ODC which persisted for 1 week, a pattern known to be associated with recovery from tissue damage and delayed cellular maturation. Pretreatment of the rats with phenoxybenzamine, an alpha-receptor blocking agent, resulted in attenuation of the long-term ODC response, but did not interfere with effects on the enzyme during the hypoxia itself. In the heart, hypoxia at 8 days of age displayed similar effects, with long-term ODC elevations which were attenuated by phenoxybenzamine. Hypoxia at 1 day of age also produced long-term heart ODC stimulation, but in this case the effect was exacerbated by phenoxybenzamine, an effect consistent with the greater dependence of cardiac tissue on alpha-receptor-mediated responses to hypoxia at that age. These results suggest that alpha-receptor stimulation by catecholamines released during neonatal hypoxia play a role in the metabolic adjustment of brain and heart tissue to damage and may aid in subsequent recovery.

Neonatal hypoxia is a major cause of morbidity and mortality in new-borns (NB). Fetal asphyxia has traditionally been diagnosed and graded using clinical signs (meconium-staining, fetal bradycardia, Apgar score [1]) and biochemical parameters (pH, lactate [2]). However, the sensitivity and specificity of these indices are not optimal and more accurate methods for assessing hypoxia are needed.