Brain Cell Membrane Function Research Articles

Effects of alpha-phenyl-N-tert-butyl nitrone (PBN)on brain cell membrane function and energy metabolism during transient global cerebral hypoxia-ischemia and reoxygenation-reperfusion in newborn piglets.

We sought to know whether a free radical spin trap agent, α-phenyl-N-tert-butyl nitrone (PBN) influences brain cell membrane function and energy metabolism during and after transient global hypoxia-ischemia (HI) in the newborn piglets. Cerebral HI was induced by temporary complete occlusion of bilateral common carotid arteries and simultaneous breathing with 8% oxygen for 30 min, followed by release of carotid occlusion and normoxic ventilation for 1 hr (reoxygenation-reperfusion, RR). PBN (100 mg/kg) or vehicle was administered intravenously just before the induction of HI or RR. Brain cortex was harvested for the biochemical analyses at the end of HI or RR. The level of conjugated dienes significantly increased and the activity of Na+, K+-ATPase significantly decreased during HI, and they did not recover during RR. The levels of ATP and phosphocreatine (PCr) significantly decreased during HI, and recovered during RR. PBN significantly decreased the level of conjugated dienes both during HI and RR, but did not influence the activity of Na+, K+-ATPase and the levels of ATP and PCr. We demonstrated that PBN effectively reduced brain cell membrane lipid peroxidation, but did not reverse ongoing brain cell membrane dysfunction nor did restore brain cellular energy depletion, in our piglet model of global hypoxic-ischemic brain injury.

Effects of MK-801 (dizocilpine) on brain cell membrane function and energy metabolism in experimental Escherichia coli meningitis in the newborn piglet.

We evaluated the efficacy of non-competitive N-methyl-D-aspartate receptor antagonist MK-801 (dizocilpine) as an adjuvant therapy in experimental neonal bacterial meningitis. Meningitis was induced by injecting 10(6) colony forming units of Escherichia coli into the cisterna magna. MK-801 3 mg/kg was given as a bolus intravenous injection, 30 min before the induction of meningitis. MK-801 did not down-modulate the inflammatory parameters, such as increased intracranial pressure, cerebrospinal fluid (CSF) leukocytosis, increased lactate and TNF-alpha levels in the CSF, and hypoglycorrhachia observed in the meningitis group. MK-801 did not significantly attenuate the elevated glutamate concentration in the CSF. However, MK-801 showed some neuroprotective effects as evidenced by significant attenuation of cerebral lipid peroxidation products (conjugated dienes) and increase of brain high-energy phosphate compounds (ATP and PCr). Improvement in cerebral cortical cell membrane Na+, K+ -ATPase activity did not reach a statistical significance. These results suggest that MK-801 was effective in ameliorating brain injury in neonatal bacterial meningitis, although it failed to attenuate the inflammatory responses.

Arsenic induced changes in growth development and apoptosis in neonatal and adult brain cells in vivo and in tissue culture

Arsenic at a nonlethal level in drinking water consumed over a period of time has been reported to produce chronic toxicity and various types of health problems ranging from skin cancer to disturbance in memory. Neurotoxic effects have been reported in clinical cases with chronic exposure to arsenic. Physiological detoxication of arsenic occurs partially through methylation. Arsenic and its methylated derivatives are distributed in different organs and systems. The present study examined the possible interference in the neuronal development and differentiation due to the exposure to arsenic during gestation. The experiments were carried out to examine short and long term effects of arsenic on brain explants and cells grown and maintained in tissue culture system. The effects of arsenic exposure showed changes in brain cell membrane function indicated by generation and release of reactive oxygen–nitrogen intermediates. On the morphological aspect the explants’ growth was reduced, ground matrix was lost and neural networking was inhibited. Cells showed signs of apoptotic changes. Arsenic toxicity may induce damage to brain cells prior to more visible clinical conditions. The deleterious effects also pass from the maternal to fetal tissue across the transplacental barrier.

Effect of α-Phenyl-N-tert-Butylnitrone on Brain Cell Membrane Function and Energy Metabolism in Experimental Escherichia coli Meningitis in the Newborn Piglet

We evaluated the efficacy of alpha-phenyl-N-tertbutylnitrone as an adjunctive therapy in experimental bacterial meningitis in the newborn piglet. Meningitis was induced by intracisternal injection of 10(8) colony-forming units of Escherichia coli in 100 microl of saline. Alpha-Phenyl-N-tert-butylnitrone 100 mg/kg was given as a bolus intravenous injection 30 min before induction of meningitis. Although it completely abolished the elevated CSF tumor necrosis factor-a level observed in the meningitis group, alpha-phenyl-N-tert-butylnitrone did not down-modulate parameters of inflammatory responses such as increased intracranial pressure, hypoglycorrhachia, elevated CSF lactate level, and CSF leukocytosis observed in this group. However, alpha-phenyl-N-tert-butylnitrone treatment mitigated alterations in brain cell membrane structure and function during meningitis, evidenced by amelioration of increased brain cell membrane lipid peroxidation products (conjugated dienes) and decreased Na+, K+-ATPase activity. Reduced mean arterial blood pressure, cerebral perfusion pressure, brain glucose concentration, and cerebral energy stores and marginally increased brain lactate level observed in the meningitis group were also ameliorated. These results suggest that although it failed to attenuate the inflammatory responses, alpha-phenyl-N-tert-butylnitrone was effective in ameliorating brain injury in neonatal bacterial meningitis.

Effect of hypothermia on bilirubin-induced alterations in brain cell membrane function and energy metabolism in newborn piglets

The aim of this study was to evaluate the effects of hypothermia on bilirubin-induced alterations in brain cell membrane function and energy metabolism in the developing brain. Thirty-seven newborn piglets were divided randomly into four groups: normothermic control (NC, n=9); hypothermic control (HC, n=7); normothermic bilirubin infusion (NB, n=11); and hypothermic bilirubin infusion (HB, n=10) groups. In bilirubin infusion groups (NB and HB), a loading dose of bilirubin (35 mg/kg) was given over 5 min, followed by a continuous infusion (25 mg/kg/h) for 4 h. The control groups (NC, HC) received a bilirubin-free buffer solution. Sulfadimethoxine was administered to animals in all experimental groups. Rectal temperature was maintained between 38.0 and 39.0°C in normothermic groups, and between 34.0 and 35.0°C in hypothermic groups for 4 h after the start of bilirubin infusion. The final blood and brain bilirubin concentrations in the bilirubin infusion groups (NB and HB) were not significantly different. Decreased cerebral cortical cell membrane Na +,K +–ATPase activity and increased lipid peroxidation products observed in the NB group, indicative of bilirubin-induced brain damage, were significantly attenuated in the HB group. Hypothermia also significantly improved the bilirubin-induced reduction in brain ATP and phosphocreatine levels and increase in blood and brain lactate levels. In summary, hypothermia significantly attenuated the bilirubin-induced alterations in brain cell membrane function and energy metabolism in the newborn piglet. These findings suggest the possibility that hypothermia could be a good neuroprotective therapeutic modality in neonatal bilirubin encephalopathy.

Effects of hyperglycemia or hypoglycemia on brain cell membrane function and energy metabolism during the immediate reoxygenation–reperfusion period after acute transient global hypoxia–ischemia in the newborn piglet

This study was done to determine the effects of hyperglycemia or hypoglycemia on brain cell membrane function and energy metabolism during the immediate reoxygenation–reperfusion period after hypoxia–ischemia (HI). Forty-five newborn piglets were divided randomly into four experimental groups: normoxia control (NC, n=9); HI/reoxygenation–reperfusion (RR) control (HC, n=11); HI/RR hyperglycemia (HE, n=12); and HI/RR hypoglycemia (HO, n=13) group. Animals were subjected to transient HI for 30 min followed by 2 h of RR. Cerebral HI was induced by temporary but complete occlusion of bilateral common carotid arteries with surgical clips and simultaneous breathing with 8% oxygen. Glucose was unregulated in HC group, and controlled by modified glucose clamp technique immediately after HI in HE (350 mg/dl) and HO (50 mg/dl) groups. During HI, heart rate, base deficit, glucose and lactate level in the blood and cerebrospinal fluid increased, and arterial pH, oxygen saturation and blood pressure decreased significantly in HC, HE and HO groups. During RR, these abnormalities returned to normal values, but lactic acidosis persisted especially in HO group. Cerebral Na +,K +-ATPase activity decreased, and lipid peroxidation products increased significantly in HC group than in NC group, and these abnormalities were significantly aggravated in HE, but not in HO, group. Brain ATP and phosphocreatine levels in HE group were significantly reduced compared to the corresponding values in NC, HC and HO groups. In summary, hyperglycemia, but not hypoglycemia immediately after HI interfered with the recovery of brain cell membrane function and energy metabolism. These findings suggest that post-hypoxic–ischemic hyperglycemia is not beneficial and might even be harmful in neonatal hypoxic–ischemic encephalopathy.

Effect of hypothermia on brain cell membrane function and energy metabolism after transient global hypoxia-ischemia in the newborn piglet.

This study was done to determine the effects of hypothermia on brain cell membrane function and energy metabolism after transient hypoxia-ischemia (HI) in the newborn piglet. Cerebral HI was induced by temporarily complete occlusion of bilateral common carotid arteries with surgical clips and simultaneous breathing with 8% oxygen for 30 min, followed by release of carotid occlusion and normoxic ventilation for 4 hr. Rectal temperature was maintained between 38.0 and 39.0 degrees C in normothermic groups, and between 34.0 and 35.0 degrees C in hypothermic groups for 4 hr after HI. During HI, heart rate, glucose and lactate level in the blood and cerebrospinal fluid increased, and base excess, pH and blood pressure decreased significantly in both normothermic and hypothermic groups. After HI, these abnormalities returned to normal in normothermic group, but lactic acidosis persisted in hypothermic group. Decreased cerebral Na+,K+- ATPase activity and increased lipid peroxidation products, indicative of HI- induced brain injury, were more profound in hypothermic group than in normothermic group. Brain ATP and phosphocreatine levels were not different between normothermic and hypothermic groups. In summary, hypothermia applied immediately after HI for 4 hr did not improve the recovery of brain cell membrane function and energy metabolism in the newborn piglet.

Effects of decreased cerebral perfusion pressure on cerebral hemodynamics, brain cell membrane function and energy metabolism during the early phase of experimental Escherichia coli meningitis in the newborn piglet.

In this study, we tested the hypothesis that decreased cerebral perfusion pressure (CPP) induces cerebral ischemia and worsen brain damage in neonatal bacterial meningitis. Meningitis was induced by intracisternal injection of 10(9) colony forming units of Escherichia coli in 21 newborn piglets. Although CPP decreased significantly at 8 hr after bacterial inoculation, deduced hemoglobin (HbD), measured as an index of changes in cerebral blood flow by near infrared spectroscopy, did not decrease significantly. In correlation analyses, CPP showed significant positive correlation with brain ATP and inverse correlation with brain lactate levels. CPP also correlated positively with HbD and oxidized cytochrome aa3 (Cyt aa3) by near infrared spectroscopy. However, CPP did not show significant correlation with cerebral cortical cell membrane Na+,K+-ATPase activity, nor with levels of lipid peroxidation products. In summary, decreased CPP observed in this study failed to induce cerebral ischemia and further brain injury, indicating that cerebrovascular autoregulation is intact during the early phase of experimental neonatal bacterial meningitis.

Effects of fasting and insulin-induced hypoglycemia on brain cell membrane function and energy metabolism during hypoxia–ischemia in newborn piglets

This study was done to determine the effects of 12 h fasting-induced mild hypoglycemia (blood glucose 60 mg/dl) and insulin-induced moderate hypoglycemia (blood glucose 35 mg/dl) on brain cell membrane function and energy metabolism during hypoxia–ischemia in newborn piglets. Sixty-three ventilated piglets were divided into six groups; normoglycemic control (NC, n=8), fasting-induced mildly hypoglycemic control (FC, n=10), insulin-induced moderately hypoglycemic control (IC, n=10), normoglycemic/hypoxic–ischemic (NH, n=11), fasting-induced mildly hypoglycemic/hypoxic–ischemic (FH, n=12) and insulin-induced moderately hypoglycemic/hypoxic–ischemic (IH, n=12) group. Cerebral hypoxia–ischemia was induced by occlusion of bilateral common carotid arteries and simultaneous breathing with 8% oxygen for 30 min. The brain lactate level was elevated in NH group and this change was attenuated in FH and IH groups. The extent of cerebral lactic acidosis during hypoxic–ischemic insult showed significant positive correlation with blood glucose level ( r=0.55, p<0.001). Cerebral Na +, K +-ATPase activity and concentrations of high-energy phosphate compounds were reduced in NH group and these changes were not ameliorated in FH or IH group. Cortical levels of conjugated dienes, measured as an index of lipid peroxidation of brain cell membrane, were significantly elevated in NH, FH and IH groups compared with NC, FC and IC groups and these increases were more profound in FH and IH with respect to NH. Blood glucose concentration showed significant inverse correlation with levels of conjugated dienes ( r=−0.35, p<0.05). These findings suggest that, unlike in adults, mild or moderate hypoglycemia, regardless of methods of induction such as fasting or insulin-induced, during cerebral hypoxia–ischemia is not beneficial and may even be harmful in neonates.

Effect of Insulin-Induced and Fasting Hypoglycemia on Brain Cell Membrane Function and Energy Metabolism during Hypoxia-Ischemia in Newborn Piglets

Effect of Insulin-Induced and Fasting Hypoglycemia on Brain Cell Membrane Function and Energy Metabolism during Hypoxia-Ischemia in Newborn Piglets

Deleterious brain cell membrane effects after NMDA receptor antagonist administration to newborn piglets

Previous studies have shown that administration of the N-methyl- d-aspartate (NMDA) receptor antagonist 3-(2-carboxypiperazin-4-yl)-1-phosphonic acid (CPP) reduces NMDA-mediated neurotoxicity in animal models of hypoxia/ischemia but also may induce brain tissue vacuolization and alter glucose metabolism. The present study tests the hypothesis that CPP administration alters brain cell membrane structure and function in the cerebral cortex of normoxic newborn piglets through the generation of oxygen free radicals and induction of lipid peroxidation. Twenty six anesthetized, ventilated newborn piglets—13 treated with 2 mg/kg i.v. CPP and 13 untreated controls—were studied. ATP and phosphocreatine (PCr) levels were measured as an index of cellular energy metabolism and tissue glucose levels determined. Na +,K +-ATPase activity was measured as an index of brain cell membrane function and the lipid peroxidation products conjugated dienes (CD) and fluorescent compounds (FC) measured. Free radical generation was detected on cortical biopsies homogenized with α-phenyl- N- tert-butyl-nitrone (PBN) through electron spin resonance spectroscopy. Signal height of spectrum was divided by dry tissue weight and expressed as mm/g tissue. In the two groups brain tissue ATP and PCr levels were not different. Tissue glucose levels were higher in the CPP group (24±5 mg/dl) than in controls (14±3 mg/dl), p<0.05, whereas Na +,K +-ATPase activity was lower in the CPP group than in controls (34±4 vs. 43±6 μmol Pi/mg protein/h), p<0.05. Lipid peroxidation products were higher in the CPP group (CD: 57±19 nmol/g brain, FC: 1.5±0.3 μg/g brain) than in controls (CD: 0±0 nmol/g brain, FC: 0.9±0.2 μg/g brain), p<0.05. Free radical intensity was higher in the CPP group (493±397 mm/g tissue) than in controls (51±83 mm/g tissue), p<0.05. In vitro administration of CPP to brain cell membranes did not change Na +,K +-ATPase activity or the generation of lipid peroxidation products. The data demonstrate that administration of CPP induces lipid peroxidation, results in free radical generation, decreases brain cell membrane Na +,K +-ATPase activity and alters glucose metabolism in the cerebral cortex of newborn piglets. Since CPP is a potent antagonist of the NMDA receptor, we speculate that CPP generates free radicals through a pathway independent of the NMDA receptor by altering cellular metabolism and possibly glucose utilization during normoxia in newborn piglets.

Effect of hyperglycemia on brain cell membrane function and energy metabolism during hypoxia–ischemia in newborn piglets

The purpose of this study was to test the hypothesis that hyperglycemia ameliorates changes in brain cell membrane function and preserves cerebral high energy phosphates during hypoxia–ischemia in newborn piglets. A total of 42 ventilated piglets were divided into 4 groups, normoglycemic/normoxic(group 1, n=9), hyperglycemic/normoxic(group 2, n=8), normoglycemic/hypoxic–ischemic(group 3, n=13) and hyperglycemic/hypoxic–ischemic(group 4, n=12) group. Cerebral hypoxia–ischemia was induced by occlusion of bilateral common carotid arteries and simultaneous breathing with 8% oxygen for 30 min. Hyperglycemia (blood glucose 350–400 mg/dl) was maintained for 90 min before and throughout hypoxia–ischemia using modified glucose clamp technique. Changes in cytochrome aa3 were continuously monitored using near infrared spectroscopy. Blood and CSF glucose and lactate were monitored. Na +, K +-ATPase activity, lipid peroxidation products (conjugated dienes), tissue high energy phosphates (ATP and phosphocreatine) levels and brain glucose and lactate levels were determined biochemically in the cerebral cortex. During hypoxia–ischemia, glucose levels in blood and CSF were significantly elevated in hyperglycemic/hypoxic–ischemic group compared with normoglycemic/hypoxic–ischemic group, but lactate levels in blood and CSF were not different between two groups. At the end of hypoxia–ischemia of group 3 and 4, ▵ Cyt aa3, Na +, K +-ATPase activity, ATP and phosphocreatine values in brain were significantly decreased compared with normoxic groups 1 and 2, but were not different between groups 3 and 4. Levels of conjugated dienes and brain lactate were significantly increased in groups 3 and 4 compared with groups 1 and 2, and were significantly elevated in group 4 than in group 3 (0.30±0.11 vs. 0.09±0.02 μmol g −1 protein, 26.4±7.6 vs. 13.1±2.6 mmol kg −1, p<0.05). These findings suggest that hyperglycemia does not reduce the changes in brain cell membrane function and does not preserve cerebral high energy phosphates during hypoxia–ischemia in newborn piglets. We speculate that hyperglycemia may be harmful during hypoxia–ischemia due to increased levels of lipid peroxidation in newborn piglet.

Effect of induced hyperglycemia on brain cell membrane function and energy metabolism during the early phase of experimental meningitis in newborn piglets

This study was done to elucidate the mechanism of hypoglycorrhachia and elevated lactate concentrations leading to neuronal dysfunction in neonatal meningitis, and to determine the effects of induced hyperglycemia on these disturbances. Thirty-eight newborn piglets were divided into three groups: 12 in the control group (CG), 12 in the normoglycemic meningitis group (NG), and 14 in the hyperglycemic meningitis group (HG). Meningitis was induced by intracisternal injection of 108 cfu of Escherichia coli. Hyperglycemia (blood glucose 300–400 mg dl −1) was induced and maintained for 60 min before induction of meningitis and throughout the experiment using modified glucose clamp technique. CSF-to-blood glucose ratio decreased significantly in NG. In HG, baseline CSF-to-blood glucose ratio was lower than two other groups, but increased at 1 h after induction of meningitis. CSF lactate concentration was increased progressively in both meningitis groups, and positively correlated with CSF leukocyte numbers ( r=0.41, p<0.001) and TNF- α level ( r=0.43, p<0.001). Brain glucose concentration was significantly increased in HG and showed inverse correlation with CSF leukocyte numbers ( r=−0.59, p<0.01). Brain lactate concentration was not significantly different among three groups and positively correlated with the CSF TNF- α level ( r=0.51, p<0.05). Lipid peroxidation products were increased in NG. Na +,K +-ATPase activity, ATP/PCr concentrations were not different among three groups. Increased intracranial pressure, CSF pleocytosis (214±59 vs. 437±214/mm 3, p<0.02) and increased lipid peroxidation products observed in NG were reduced in HG. These results suggest that hypoglycorrhachia and elevated lactate concentration in the CSF during meningitis originates primarily from the increased anaerobic glycolysis in the subarachnoid space, induced by TNF- α and leukocytes. Induced hyperglycemia attenuates the inflammatory responses of meningitis and might be beneficial by providing an increased glucose delivery to meet its increased demand in meningitis.

Direct measurement of oxygen free radicals during in utero hypoxia in the fetal guinea pig brain

The present study tested the hypothesis that maternal hypoxia induces oxygen free radical generation in the fetal guinea pig brain utilizing techniques of electron spin resonance spectroscopy and alpha-phenyl- tert-butyl nitrone (PBN) spin trapping. Pregnant guinea pigs of 60 days gestation were divided into normoxic and hypoxic groups and exposed to 21% or 7% oxygen for 60 min. Free radical generation was documented by measuring the signal of PBN spin adducts. Fluorescent compounds were determined as an index of lipid peroxidation and the activity of Na +,K +-ATPase was determined as an index of brain cell membrane function. Hypoxic fetal cerebral cortical tissue showed a significant increase in spin adducts (normoxic: 33.8±9.3 units/g tissue vs. hypoxic: 57.9±9.2 units/g tissue, p<0.01) and fluorescent compounds (normoxic: 0.639±0.054 μg quinine sulfate/g brain vs. 0.810±0.102 μg quinine sulfate/g brain, p<0.01) and a decrease in Na +,K +-ATPase activity (normoxic: 43.04±2.50 μmol Pi/mg protein/h vs. hypoxic: 33.80±3.51 μmol Pi/mg protein/h, p<0.001). These results demonstrate an increased free radical generation during hypoxia in the fetal guinea pig brain. The spectral characteristics of the radicals were consistent with those of alkoxyl radicals. The increased level of fluorescent compounds and decreased activity of Na +,K +-ATPase indicated hypoxia induced brain cell membrane lipid peroxidation and dysfunction, respectively. These results directly demonstrate an increased oxygen free radical generation during hypoxia and suggest that hypoxia-induced increase in lipid peroxidation and decrease in membrane function, as indicated by a decrease in Na +,K +-ATPase activity, are consequences of increased free radicals. The nature of predominantly present alkoxyl radical indicates ongoing lipid peroxidation during hypoxia. The direct demonstration of oxygen free radical generation during hypoxia is the critical missing link in the mechanism of hypoxia-induced brain cell membrane dysfunction and damage.

The Effect of Allopurinol on NMDA Receptor Characteristics in the Brain of Fetal Guinea Pigs Following In Utero Hypoxia and Recovery • 214

The present study tests the hypothesis that maternal treatment with allopurinol following in utero hypoxia will attenuate hypoxia induced alterations of the NMDA receptor in the fetal guinea pig brain during recovery. Twenty-eight pregnant guinea pigs at term were studied. Fetuses from normoxic (n=9) and hypoxia (n=7) animals were compared to fetuses from untreated (n=7) and allopurinol treated (n=5) animals exposed to hypoxia but allowed to recover in utero for 24 hours. Maternal hypoxia was induced by lowering inspired oxygen to 7% for 1 hour. Following hypoxia the treated group immediately received 600 mg p.o allopurinol prior to recovery. Brain cell membrane Na+, K+ -ATPase activity was measured as an index of brain cell membrane function. Na+, K+ -ATPase activity was lower in the hypoxic group compared to control (40.7 ± 5.2 vs 29.5 ± 5.2 mmoles Pi/mg protein/hr, P 0.05) indicating increased receptor affinity following hypoxia and recovery. However, the Kd of the allopurinol treated recovery group was similar to control (6.11±0.76 nM). The data shows that allopurinol treatment following in utero hypoxia attenuates hypoxia induced alterations in the NMDA receptor characteristics of fetal guinea pigs during recovery. We speculate that alterations in the NMDA receptor following in utero hypoxia can be modified during recovery by treatment with allopurinol and may prevent delayed brain cell injury.

Effect of Hyperglycemia on Brain Cell Membrane Function and Energy Metabolism During Hypoxia-Ischemia in Newborn Piglets. † 840

The present study tests the hypothesis that hyperglycemia ameliorates changes in brain cell membrane function and preserves cerebral high energy phosphates during hypoxia-ischemia in newborn piglets. 41 ventilated piglets were divided into 4 groups: Gr 1 (normoxic/ normoglycemic, n=9), Gr 2(normoxic/hyperglycemic, n=8), Gr 3 (hypoxic-ischemic [HI]/normoglycemic, n=13) and Gr 4 (HI/hyperglycemic n=11). Cerebral HI was induced by 8% oxygen and occlusion of bilateral common carotid arteries for 30 min. Hyperglycemia(blood glucose 20 mmol/L) was maintained for 90 min before and throughout HI. Changes in cytochrome aa3 (Cytaa3) were continuously monitored using near infrared spectroscopy. Blood and CSF glucose and lactate were monitored. Na+,K+-ATPase activity, lipid peroxidation products (conjugated dienes [CDs]) and tissue high energy phosphates (ATP and phosphocreatine[PCr]) levels were determined biochemically in the cerebral cortex. During HI glucose levels in blood and CSF were significantly elevated in Gr 4 (21.1± 3.7, 13.7 ± 2.0) compared with Gr 3 (6.7 ± 2.4, 4.1± 0.8 mmol/L, mean ± SD p<0.05), but lactate levels in blood and CSF were not different between Gr 3 and Gr 4. In HI Gr 3 and 4, Δ Cyt aa3, Na+,K+-ATPase activity, [ATP] and [PCr] values were significantly decreased compared with normoxic Gr 1 and 2 but were not different between Gr 3 and 4. [CDs] were significantly increased in Gr 3 and 4 compared with Gr 1 and 2, and were significantly elevated in Gr 4 than Gr 3(0.30±0.11 vs 0.09±0.02 μmol/g protein, p<0.05). We conclude that hyperglycemia is not neuroprotective and does not preserve cerebral high energy phosphates during HI in piglets. We speculate that hyperglycemia may be harmful during HI due to increased levels of lipid peroxidation. (Funded by SBRI C-95-019-2 and HMP-96-M-2-107).

Effect of Rutin on Brain Cell Membrane Function and Lipid Peroxidation During Cerebral Hypoxia in Newborn Piglets † 933

Effect of Rutin on Brain Cell Membrane Function and Lipid Peroxidation During Cerebral Hypoxia in Newborn Piglets † 933

NMDA Receptor Characteristics in the Brain of Fetal Guinea Pigs Following In Utero Hypoxia and Recovery. † 201

Previous studies have shown that in utero hypoxia results in brain cell membrane dysfunction and alters N-methyl-D-aspartate (NMDA) receptor characteristics in fetal guinea pigs. The present study tests the hypothesis that modification of brain cell membrane function during in utero hypoxia persists following recovery. Six pregnant guinea pigs at term were exposed to 7% oxygen for 1 hour. Brain tissue obtained from fetal guinea pigs immediately after in utero hypoxia was compared to that of fetuses exposed to hypoxia but allowed to recover in utero for 24 hours. ATP and phosphocreatine (PCr) levels were determined biochemically as indices of brain tissue energy metabolism. ATP and PCr levels were significantly higher in the recovery group compared to the hypoxic group(5.22±0.95 vs. 1.5±0.02 and 3.73±0.28 vs. 0.66±0.17 μ mol/g brain, respectively, p<0.01). Brain cell membrane Na+,K+-ATPase activity was measured as an index of brain cell membrane function. The recovery group demonstrated a significantly higher activity of Na+,K+-ATPase compared to the hypoxic group(35.1±4.0 vs. 25.2±7.0 μ moles Pi/mg protein/hr, p<0.05).3[H]MK-801 binding (2.5-50 nM) in the presence of glutamate and glycine was performed as an index of NMDA receptor modification. Receptor number(Bmax) in the recovery group was similar to the hypoxic group(1.28±0.04 vs 1.25±0.18 pmol/mg protein). In addition receptor dissociation constant (Kd) was similar in the two groups (5.61±0.30 vs 4.94±0.84 nM). This preliminary data show that following recovery from in utero hypoxia, brain cell energy metabolism and brain cell membrane function improve, but that hypoxia-induced alterations in NMDA receptor characteristics persist. We speculate that alterations in the NMDA receptor following in utero hypoxia may contribute to delayed brain cell injury despite recovery of cellular energy metabolism and cell membrane function.

Delayed Changes in Brain Cell Membrane Function, Cytochrome aa3 and Energy Metabolism after Transient Hypoxia-Ischemia in Newborn Piglets 1713

Delayed Changes in Brain Cell Membrane Function, Cytochrome aa3 and Energy Metabolism after Transient Hypoxia-Ischemia in Newborn Piglets 1713

EFFECT OF MATERNAL MAGNESIUM SULFATE ADMINISTRATION ON BRAIN CELL FUNCTION IN THE COCAINE-EXPOSED FETAL GUINEA PIG. • 429

Previous studies from our laboratory have shown that prenatal cocaine exposure alters brain cell membrane function by decreasing membrane Na+,K+-ATPase activity and potentiates the glutamate/glycine-dependent activation of the NMDA receptor. Magnesium sulfate(MgSO4) attenuates neuronal membrane dysfunction in hypoxic newborn piglets by preserving N-methyl-D-aspartate (NMDA) receptor number and affinity, and Na+,K+-ATPase activity. Data describing the interaction of cocaine and magnesium on neuronal function are lacking. The present study tests the hypothesis that maternal MgSO4 administration will prevent cocaine-induced NMDA receptor/ion channel modification in the fetus. Studies were performed in 6 pregnant guinea pigs (58 days gestation) assigned to 3 groups: Cocaine-treated (COC, n= 2). Magnesium-treated (MG, n=2) and Magnesium/Cocaine-treated (MG-COC, n=2). Animals in the MG and MG-COC groups received an initial bolus of MgSO4 300 mg/kg i.p. followed by 50 mg/kg q 30 min for 5 hours. Mean maternal [Mg++] was 10.5 mg%. Cocaine HCl 30 mg i.p. was given to the COC and MG-COC groups one hour prior to delivery of the fetuses. 3[H]MK-801 binding studies, an index of NMDA receptor activation, were performed in a concentration range from 0.5 to 50 nM in a reaction medium containing 10mM HEPES (pH 7.0), 100 μM glutamate and glycine, and 75 μg protein. Total number of receptors (Bmax) in the COC, MG and MG-COC groups were 1.08 ± 0.13, 1.34 ± 0.07 and 1.19± 0.09 pmol/mg protein (mean±SD). Kd for the same groups were 2.64 ± 0.22, 5.18 ± 0.87 and 4.65 ± 0.01 nM. The data show that MgSO4 may prevent the cocaine-induced increase in the affinity (decreased Kd) of the NMDA receptor for 3[H]MK-801 in fetal brains. We speculate that cocaine-induced modification of the NMDA receptor ion/channel complex may alter NMDA-mediated developmental processes that are essential for fetal brain function. Furthermore, administration of MgSO4 to cocaine-exposed fetuses may attenuate neurotoxicity by the glutamate-type NMDA receptor in the developing fetal brain. (Funded by NIH-HD-20337, MOD#6- FY94-0135, UCPR 506-93)