Effects Of Hypoxia-ischemia Research Articles

Diagnostic Value of Erythropoietin Levels in Umbilical Cord Blood in Hypoxic-Ischemic Brain Injury: Clinical Observational Cross-Sectional Study

Background. In recent years erythropoietin has received particular attention due to the discovery of its important non-haematological effects. Erythropoietin is recognized as a pluripotent glycoprotein, manifesting neurotropic and neuroprotective properties as well as participating in angio-, neuro- and oligodendrogenesis, interferes with the effects of hypoxia-ischemia, oxidative stress and associated with them inflammation and apoptosis in the brain. During fetal hypoxia, the dominant production of erythropoietin switches to the placenta, starting its active synthesis to protect the brain, heart and other vital organs from harmful effects of severe hypoxia.Objectives. The study was aimed at determining the correlation between the severity of hypoxic ischemic brain injury and erythropoietin level in the artery and vein of the umbilical cord.Methods. A clinical observational cross-sectional study was conducted on the basis of the Maternity Hospital, Neonatal Pathology and Pediatric Departments №1 and №2 of the Research Institute of Obstetrics and Pediatrics under the auspices of Rostov State Medical University, Russian Federation. The study included 184 newborns with moderate (group II, n = 78) and severe hypoxic ischemic injury of the central nervous system (group III, n = 42). Group I consisted of 64 children without signs of central nervous system injury in the early neonatal period. Among which, following the maternal medical histories, 40 newborns were allocated to the group with the apparent development of delayed manifestation of neurological pathology. The evaluation of erythropoietin concentration in the umbilical cord blood was conducted separately in the artery and vein with Erythropoietin-EIA-BEST, a set of reagents for the enzyme-linked determination of erythropoietin concentration in the blood serum. Statistical analysis was carried out via MS Excel 2019 (Microsoft, USA), Statistica 12.5, (IBM, USA), SPSS27.001.Results. Erythropoietin concentrations in the blood of the artery and vein of the umbilical cord in the groups of newborns were determined according to the severity of hypoxic-ischemic brain injury. The authors of the study showed the correlation between the “maternal-placental-fetal” blood flow at 36–40 weeks of gestation, which parameters are important antenatal predictors of the central nervous system injury, and the values of erythropoietin in arterial and venous umbilical cord blood as diagnostic markers.Conclusion. The severity of cerebral abnormalities is determined by a high level of erythropoietin, while a decrease in erythropoietin level with severe cerebral deficit can mark a disabling injury.

Impact of hypoxia-ischemia and dopamine treatment on dopamine receptor binding density in the preterm fetal sheep brain.

Dopamine is often used to treat hypotension in preterm infants who are at risk of hypoxic-ischemic (HI) brain injury due to cerebral hypoperfusion and impaired autoregulation. There is evidence that systemically administered dopamine crosses the preterm blood-brain barrier. However, the effects of exogenous dopamine and cerebral HI on dopaminergic signaling in the immature brain are unknown. We determined the effect of HI and dopamine on D1 and D2 receptor binding and expressions of dopamine transporter (DAT) and tyrosine hydroxylase (TH) in the striatum of the preterm fetal sheep. Fetal sheep (99 days of gestation, term = 147days) were unoperated controls (n = 6) or exposed to severe HI using umbilical cord occlusion and saline infusion (UCO + saline, n = 8) or to HI with dopamine infusion (UCO + dopamine, 10 µg/kg/min, n = 7) for 74 h. D1 and D2 receptor densities were measured by autoradiography in vitro. DAT, TH, and cell death were measured using immunohistochemistry. HI resulted in cell death in the caudate nucleus and putamen, and dopamine infusion started before HI did not exacerbate or ameliorate these effects. HI led to reduced D1 and D2 receptor densities in the caudate nucleus and reduction in DAT protein expression in the caudate and putamen. Fetal brains exposed to dopamine in addition to HI were not different from those exposed to HI alone in these changes in dopaminergic parameters. We conclude that dopamine infusion does not alter the striatal cell death or the reductions in D1 and D2 receptor densities and DAT protein expression induced by HI in the preterm brain.NEW & NOTEWORTHY This is the first study on the effects of hypoxia-ischemia and dopamine treatment on the dopaminergic pathway in the preterm brain. In the striatum of fetal sheep (equivalent to ∼26-28 wk of human gestation), we demonstrate that hypoxia-ischemia leads to cell death, reduces D1 and D2 receptors, and reduces dopamine transporter. Intravenous dopamine infusion at clinical dosage used in preterm human infants does not alter the striatal cell death, D1 and D2 receptor density levels, and DAT protein expressions after hypoxia-ischemia in the preterm brain.

AN INDIRECT PATHWAY FOR GENETIC INFLUENCE ON THE FORMATION OF THE CEREBRAL PALSY PHENOTYPE: GENOME AND HYPOXIA TOLERANCE

The incidence of cerebral palsy is increasing. In 70% of cases, the disease develops as a result of exposure to known pathogenesis factors, such as hypoxia-ischemia, infectious, toxic, and traumatic damage to the fetus. In 30% of cases of the disease, the effect of pathogenetic factors is absent. This determines the relevance of the search for genetic anomalies responsible for the formation of this phenotype. Many genome disorders associated with the development of the cerebral palsy phenotype have been identified. Of particular interest is the indirect influence of genetic factors of pathogenesis, affecting the formation of the disease indirectly, through the mechanisms of formation of hypoxic-ischemic brain damage. Such factors affect almost all stages of the “ischemic cascade”: the formation of a “glutamate shock”, the realization of a “glutamate shock” by cytokines, the defect of the antioxidant defense of a neuron, the realization of the cytotoxic effect of nitric oxide (NO), and the stimulation of apoptosis of neurons and microglia. This makes it possible to identify genome variants that determine the tolerance of the child’s brain to hypoxic-ischemic damage. The combination of carriers of such anomalies into risk groups will make it possible to differentiate the tactics of their observation in the natal and postnatal periods in order to reduce the likelihood of the formation of severe hypoxic-ischemic lesions of the central nervous system and cerebral palsy. Today, a large amount of scientific data has been accumulated on the molecular genetic mechanisms of the pathogenesis of perinatal brain lesions. Such as epigenetic, transcriptome gene expression control mechanisms via micro-RNA. The available information allows us to experimentally develop new methods for protecting the fetal brain from hypoxia-ischemia and stopping the effects of hypoxia-ischemia in the neonatal period.

Effects of hypoxia ischemia on caspase-3 expression and neuronal apoptosis in the brain of neonatal mice.

Effects of hypoxia ischemia on caspase-3 expression and neuronal apoptosis in the brain of neonatal mice were investigated. Twenty-five neonatal CD1 mice aged 1 week were selected and randomly divided into sham-operation group (n=8) and newborn hypoxia ischemia encephalopathy (NHIE) model group (n=17). The messenger ribonucleic acid (mRNA) expression levels of caspase-3 and Fas ligand (FasL) in brain tissues of mice in both groups were detected via reverse transcription-polymerase chain reaction (RT-PCR). The protein expression levels of caspase-3 and FasL in mice in both groups were detected via western blotting. Moreover, apoptosis of brain tissues was detected using the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL), and caspase-3 protein expression level in brain tissues was detected using immunohistochemical methods. Results of RT-PCR and western blotting revealed that compared with those in sham-operation group, caspase-3 and FasL expression levels in model group were significantly increased. Results of TUNEL showed that the number of apoptotic neurons in model group was significantly increased. Besides, results of immunohistochemical detection manifested that the caspase-3 protein expression level in model group was obviously increased. Hypoxia ischemia can lead to significant increase of caspase-3 expression and increase of neuronal apoptosis in the brain of neonatal mice.

Effects of hypoxia-ischemia and inotropes on expression of cardiac adrenoceptors in the preterm fetal sheep.

Preterm infants frequently suffer cardiovascular compromise, with hypotension and/or low systemic blood flow, leading to tissue hypoxia-ischemia (HI). Many preterm infants respond inadequately to inotropic treatments using adrenergic agonists such as dobutamine (DB) or dopamine (DA). This may be because of altered cardiac adrenoceptor expression because of tissue HI or prolonged exposure to adrenergic agonists. We assessed the effects of severe HI with and without DB/DA treatment on cardiac adrenoceptor expression in preterm fetal sheep. Fetal sheep (93-95 days) exposed to sham surgery or severe HI induced by umbilical cord occlusion received intravenous DB or saline for 74 h (HI + DB, HI, Sham + DB, Sham). The HI groups were also compared with fetal sheep exposed to HI and DA. Fetal hearts were collected to determine β-adrenoceptor numbers using [125I]-cyanopindolol binding and mRNA expression of β1-, β2-, α1A-, α2A-, or α2B-adrenoceptors. The HI group had increased β-adrenoceptor numbers compared with all other groups in all four heart chambers ( P < 0.05). This increase in β-adrenoceptor numbers in the HI group was significantly reduced by DB infusion in all four heart chambers, but DA infusion in the HI group only reduced β-adrenoceptor numbers in the left atria and ventricle. DB alone did not affect β-adrenoceptor numbers in the sham animals. Changes in β1-adrenoceptor mRNA levels trended to parallel the binding results. We conclude that HI upregulates preterm fetal cardiac β-adrenoceptors, but prolonged exposure to adrenergic agonists downregulates adrenoceptors in the preterm heart exposed to HI and may underpin the frequent failure of inotropic therapy in preterm infants. NEW & NOTEWORTHY This is the first study, to our knowledge, on the effects of hypoxia-ischemia and adrenergic agonists on adrenoceptors in the preterm heart. In fetal sheep, we demonstrate that hypoxia-ischemia increases cardiac β-adrenoceptor numbers. However, exposure to both hypoxia-ischemia and adrenergic agonists (dobutamine or dopamine) reduces the increase in β-adrenoceptor numbers, which may underpin the inadequate response in human preterm infants to inotropic therapy using adrenergic agonists. Dobutamine alone does not affect the cardiac adrenoceptors in the sham animals.

Vitamin D insufficiency in neonatal hypoxic-ischemic encephalopathy.

BackgroundVitamin D has neuroprotective and immunomodulatory properties, and deficiency is associated with worse stroke outcomes. Little is known about effects of hypoxia-ischemia or hypothermia treatment on vitamin D status in neonates with hypoxic-ischemic encephalopathy (HIE). We hypothesized vitamin D metabolism would be dysregulated in neonatal HIE altering specific cytokines involved in Th17 activation, which might be mitigated by hypothermia.MethodsWe analyzed short term relationships between 25(OH) and 1,25(OH)2 vitamin D, vitamin D binding protein, and cytokines related to Th17 function in serum samples from a multicenter randomized controlled trial of hypothermia 33°C for 48h after HIE birth versus normothermia in 50 infants with moderate to severe HIE.ResultsInsufficiency of 25(OH) vitamin D was observed after birth in 70% of infants, with further decline over the first 72h, regardless of treatment. 25(OH) vitamin D positively correlated with antiinflammatory cytokine IL-17E in all HIE infants. However, Th17 cytokine suppressor IL-27 was significantly increased by hypothermia, negating the IL-27 correlation with vitamin D observed in normothermic HIE infants.ConclusionsSerum 25(OH) vitamin D insufficiency is present in the majority of term HIE neonates and is related to lower circulating anti-inflammatory IL-17E. Hypothermia does not mitigate vitamin D deficiency in HIE.

In vivo Monitoring of Cerebral Hemodynamics in the Immature Rat: Effects of Hypoxia-Ischemia and Hypothermia

Background: Neonatal hypoxic-ischemic (HI) encephalopathy occurs in 1-4 per 1,000 live term births and can cause devastating neurodevelopmental disabilities. Currently, therapeutic hypothermia (TH) is the only treatment with proven efficacy. Since TH is associated with decreased cerebral metabolism and cerebral blood flow (CBF), it is important to assess CBF at the bedside. Diffuse correlation spectroscopy (DCS) has emerged as a promising optical modality to noninvasively assess an index of CBF (CBF_i) in both humans and animals. In this initial descriptive study, we employ DCS to monitor the evolution of CBF_i following HI with or without TH in immature rats. We investigate potential relationships between CBF and subsequent cerebral damage. Methods: HI was induced on postnatal day 10 or 11 rat pups by right common carotid artery ligation followed by 60-70 min hypoxia (8% oxygen). After HI, the pups recovered for 4 h under hypothermia (HI-TH group, n = 23) or normothermia (HI-N group, n = 23). Bilateral measurements of hemispheric CBF_i were made with DCS in unanesthetized animals at baseline, before HI, and 0, 1, 2, 3, 4, 5, and 24 h after HI. The animals were sacrificed at either 1 or 4 weeks, and brain injury was scored on an ordinal scale of 0-5 (0 = no injury). Results: Carotid ligation caused moderate bilateral decreases in CBF_i. Following HI, an initial hyperemia was observed that was more prominent in the contralateral hemisphere. After initiation of TH, CBF_i dropped significantly below baseline levels and remained reduced for the duration of TH. In contrast, CBF_i in the HI-N group was not significantly decreased from baseline levels. Reductions in CBF_i after 4 h of TH were not associated with reduced damage at 1 or 4 weeks. However, elevated ipsilateral CBF_i and ipsilateral-to-contralateral CBF_i ratios at 24 h were associated with worse outcome at 1 week after HI. Conclusions: Both HI and TH alter CBF_i, with significant differences in CBF_i between hypothermic and normothermic groups after HI. CBF_i may be a useful biomarker of subsequent cerebral damage.

The Effects of Hypoxia-Ischemia on Neutral Amino Acid Transporters in the Developing Rat Brain

The neutral amino acid transporters SNAT1–3 and ASCT1 play critical roles in the recycling of glutamine, and subsequently glutamate, via the glutamine-glutamate cycle. Hypoxia-ischemia was induced in rat pups using the Rice-Vannucci model. Brains were harvested at 1 h, 24 h and 7 days after ischemia. The expression of NAATs was evaluated using immunoblotting, real-time PCR, and immunohistochemistry. Results were compared with age-matched controls and shams. SNAT1 mRNA decreased at 1 h after injury in both hemispheres when compared with the control animals and correlated with a decrease in protein expression at 24 h in the hippocampus and cortex. SNAT1 protein expression increased globally at 7 days after injury and specifically in the hippocampus. Finally, SNAT2 and 3 demonstrated subtle changes in various brain regions after injury. These data suggest that neutral amino acid transporters remain largely intact after hypoxia-ischemia.

Less Neurogenesis and Inflammation in the Immature than in the Juvenile Brain after Cerebral Hypoxia-Ischemia

The effects of hypoxia-ischemia (HI) on proliferation and differentiation in the immature (postnatal day 9) and juvenile (postnatal day 21) mouse hippocampus were investigated by injecting bromodeoxyuridine (50 mg/kg) daily for 7 days after the insult and evaluating the labeling 5 weeks after HI. Phenotypic differentiation was evaluated using NeuN, Iba1, APC, and S100beta as markers of neurons, microglia, oligodendrocytes, and astrocytes, respectively. The basal proliferation, in particular neurogenesis, was higher in the immature than in the juvenile hippocampus. Hypoxia-ischemia did not increase neurogenesis significantly in the immature dentate gyrus (DG), but it increased several-fold in the juvenile brain, reaching the same level as in the normal, noninjured immature brain. This suggests that the immature hippocampus is already working at the top of its proliferative capacity and that even though basal neurogenesis decreased with age, the injury-induced generation of new neurons in the juvenile hippocampus could not increase beyond the basal level of the immature brain. Generation of glial cells of all three types after HI was significantly more pronounced in the cornu ammonis of the hippocampus region of the juvenile hippocampus. In the DG, only microglia production was greater in the juvenile brain. Increased microglia proliferation correlated with increased levels of the proinflammatory cytokines MCP-1 and IL-18 3 days after HI, indicating that the inflammatory response is stronger in the juvenile hippocampus. In summary, contrary to what has been generally assumed, our results indicate that the juvenile brain has a greater capacity for neurogenesis after injury than the immature brain.

Effects of hypoxia-ischemia and inhibition of nitric oxide synthase on cerebral energy metabolism in newborn piglets.

The present study was designed to examine the effects of inhibition of nitric oxide synthase on cerebral energy metabolism after hypoxia-ischemia in newborn piglets. Ten 1- to 3-d-old piglets received N(omega)-nitro-L-arginine (NNLA), an inhibitor of nitric oxide synthase (NNLA-hypoxia, n = 5), or normal saline (hypoxia, n = 5) 1 h before cerebral hypoxia-ischemia. After the infusion, hypoxia-ischemia was induced by bilateral occlusion of the carotid arteries and decreasing FiO2 to 0.07 and maintained for 60 min. Thereafter, animals were resuscitated and ventilated for another 3 h. Using 1H- and 31P-magnetic resonance spectroscopy, cerebral energy metabolism was measured in vivo at 15-min intervals throughout the experiment. Phosphocreatine to inorganic phosphate ratios decreased from 2.74 +/- 0.14 to 0.74 +/- 0.36 (hypoxia group) and 2.32 +/- 0.17 to 0.18 +/- 0.10 (NNLA-hypoxia group) during hypoxia-ischemia. Thereafter, phosphocreatine to inorganic phosphate ratios returned rapidly to baseline values in the hypoxia group, but remained below baseline values in the NNLA-hypoxia group. Intracellular pH decreased during hypoxia-ischemia and returned to baseline values on reperfusion in both groups. Intracellular pH values were lower in the NNLA-hypoxia group (p < 0.001, ANOVA). Lactate was not present during the baseline period. After hypoxia-ischemia, lactate to N-acetylaspartate ratios increased to 1.34 +/- 0.28 (hypoxia group) and 2.22 +/- 0.46 (NNLA-hypoxia group). Lactate had disappeared after 3 h of reperfusion in the hypoxia group, whereas lactate to N-acetylaspartate ratios were 1.37 +/- 1.37 in the NNLA-hypoxia group. ANOVA demonstrated a significant effect of NNLA on lactate to N-acetylaspartate ratios (p < 0.001). Inhibition of nitric oxide synthase by NNLA tended to compromise cerebral energy status during and after cerebral hypoxia-ischemia in newborn piglets.

Effects of neonatal cerebral hypoxia-ischemia on the in vitro phosphorylation of synapsin 1 in rat synaptosomes.

Synapsins are phosphoproteins related to the anchorage of synaptic vesicles to the actin skeleton. Hypoxia-ischemia causes an increased calcium influx into neurons through ionic channels gated by activation of glutamate receptors. In this work seven-day-old Wistar rats were submitted to hypoxia-ischemia and sacrificed after 21 hours, 7, 30, or 90 days. Synaptosomal fractions were obtained by Percoll gradients and incubated with 32P (10 microCi/g). Proteins were analysed by SDS-PAGE and radioactivity incorporated into synapsin 1 was counted by liquid scintillation. Twenty-one hours after hypoxia-ischemia we observed a reduction on the in vitro phosphorylation of synapsin 1, mainly due to hypoxia, rather than to ischemia; this effect was reversed at day 7 after the insult. There was another decrease in phosphorylation 30 days after the event interpreted as a late effect of hypoxia-ischemia. No changes were observed at day 90. Our results suggest that decreased phosphorylation of synapsin 1 could be related to neuronal death that follows hypoxia-ischemia.

The effects of hypoxia-ischemia on expression of c-Fos, c-Jun and Hsp70 in the young rat hippocampus.

The expression of c-Fos, c-Jun and Hsp70 was examined in the hippocampus at 6, 12, 24, 48, 72 h, 4, 7 and 42 days following a combination of unilateral common carotid artery ligation and 60 min of systemic hypoxia (8% oxygen, 92% nitrogen) in 25-day-old male rats. While pyknotic cells were not visible in the hippocampus of control animals, pyknosis was evident in the ipsilateral, but not the contralateral hippocampus, of hypoxic-ischemic animals beginning at 24 h post-hypoxia. Immunohistochemical analysis revealed no c-Fos-, c-Jun- or Hsp70-immunoreactivity (IR) in any control animals. However, at 6 h post-hypoxia, Fos- and Jun-IR was evident throughout the injured ipsilateral hippocampus and later appeared throughout the contralateral hippocampus, which never showed signs of pyknosis. In contrast, Hsp70-IR was first observed at 24 h post-hypoxia and was restricted to the injured ipsilateral hippocampus. Hsp70-IR was not, however, limited to dying neurons. H-I/seizure animals did not express these proteins at any time point. These results suggest that, even in irreversibly injured neurons, Fos, Jun and Hsp70 appear to be involved in the aftermath of ischemia but probably do not play a pivotal role in the outcome of H-I compromised cells. Furthermore, compounded injury (H-I/seizure) appears to block the synthesis these proteins.

Effects of hypoxia-ischemia on GLUT1 and GLUT3 glucose transporters in immature rat brain.

Cerebral hypoxia-ischemia produces major alterations in energy metabolism and glucose utilization in brain. The facilitative glucose transporter proteins mediate the transport of glucose across the blood-brain barrier (BBB) (55 kDa GLUT1) and into the neurons and glia (GLUT3 and 45 kDa GLUT1). Glucose uptake and utilization are low in the immature rat brain, as are the levels of the glucose transporter proteins. This study investigated the effect of cerebral hypoxia-ischemia in a model of unilateral brain damage on the expression of GLUT1 and GLUT3 in the ipsilateral (damaged, hypoxic-ischemic) and contralateral (undamaged, hypoxic) hemispheres of perinatal rat brain. Early in the recovery period, both hemispheres exhibited increased expression of BBB GLUT1 and GLUT3, consistent with increased glucose transport and utilization. Further into recovery, BBB GLUT1 increased and neuronal GLUT3 decreased in the damaged hemisphere only, commensurate with neuronal loss.

Alterations of Brain Levels of Phosphoinositidase-C–Linked Gqα/G11α Proteins and Motor Function in Rats After Cardiac Arrest

Phosphoinositidase-C-linked Gq alpha and G11 alpha proteins have only recently been characterized. Second messenger systems are known to be affected by hypoxia-ischemia. However, the effects of hypoxia-ischemia on the brain levels of Gq alpha and G11 alpha proteins are not known. Therefore, in the present studies, the effects of hypoxia-ischemia on Gq alpha and G11 alpha proteins in rats were investigated with quantitative immunoblot analysis. Cardiac arrest was induced in male Sprague-Dawley rats by an intracardial injection of KCl. Resuscitation began 10 minutes afterwards. At various time points after resuscitation, animals were killed and the cerebral cortex, striatum, and cerebellum were dissected. Levels of Gq alpha and G11 alpha proteins were investigated by quantitative immunoblot analysis. At 1, 2, 4, and 6 hours after resuscitation, Gq alpha and G11 alpha protein levels remained unaltered. However, a significant reduction of these proteins was seen in the cerebral cortex and cerebellum of rats 3 and 14 days after cardiac arrest, with partial recovery by an average of 60 days. In contrast, no significant change was detected in the striatum. These observations indicate that phosphoinositidase-C-linked signal transduction pathways may be attenuated after hypoxic-ischemic insults to the brain, and that this phenomenon, together with many other factors, may contribute to the expression of motor dysfunction in rats after cardiac arrest.

Effects of hypoxia-ischemia and seizures on neuronal and glial-like c- fos protein levels in the infant rat

Unilateral carotid ligation in immature rats, followed by 2 h of hypoxia led to ischemic cell change from 2 h after the insult, on the ligated side of the brain. There was a time-dependent induction of immunoreactive c- fos protein in neurones but not glia or ependyma on the non-ligated side of the brain. Induction only occurred in rats that had seizures post hypoxia-ischemia. In the ligated hemisphere c- fos protein was induced in glial-like cells in the corpus callosum, fornix/fimbria and internal capsule and in ependymal cells lining the lateral ventricle starting from 2 h after hypoxia but subsiding by 3 days. No neuronal c- fos induction was seen in areas showing neuronal damage. MK-801 or carbamazepine, which prevented hypoxia-ischemia-induced seizures, also prevented c- fos induction in the non-ligated hemisphere while MK-801 was associated with increased c- fos induction in hippocampal neurones from the ligated side, as well as in glial-like and ependymal cells. These results suggest several processes are involved following the hypoxic-ischemic insult. Firstly, severe hypoxia-ischemia is associated with a reduction in neuronal c- fos protein levels, probably as a result of neuronal failure and death. Secondly, post hypoxic seizures cause c- fos induction in surviving neurones. Thirdly, glial-like from regions in which there is neural loss also exhibit induction of c- fos, which may be important for their subsequent proliferation or for the production of growth factors.

Effects of hypoxia-ischemia and MK-801 treatment on the binding of a phencyclidine analogue in the developing rat brain.

The phencyclidine analogue [3H](1-[2-thienyl]cyclohexyl)piperidine (3H-TCP) binds to the ion channel associated with the N-methyl-D-aspartate receptor channel complex. In vitro autoradiography indicates that the distribution of 3H-TCP binding in brain closely parallels that of [3H]glutamate binding to the N-methyl-D-aspartate receptor. In nine 7-day-old rats, an acute focal hypoxic-ischemic insult produced by unilateral carotid artery ligation and subsequent exposure to 8% oxygen acutely reduced 3H-TCP binding ipsilateral to the ligation by 30% in the CA1, by 27% in the CA3, by 26% in the dentate gyrus, and by 17% in the striatum compared with values from the contralateral hemisphere. In 10 littermates that received 1 mg/kg of the neuroprotective noncompetitive N-methyl-D-aspartate antagonist MK-801 immediately before hypoxic exposure, the regional distribution of 3H-TCP binding in hypoxic-ischemic brain was relatively preserved and there were no interhemispheric asymmetries in 3H-TCP binding densities. In addition, in three unoperated rats decapitated 24 hours after MK-801 treatment, 3H-TCP binding was reduced by 15-35%; similar bilateral suppression of 3H-TCP binding was detected in MK-801-treated ligates. Our data indicate that 3H-TCP autoradiography can be used to assay the efficacy of neuroprotective agents in this experimental model of perinatal stroke.