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Mitra S, Bale G, Mathieson S, Uria-Avellanal C, Meek J, Tachtsidis I, Robertson NJ. Changes in Cerebral Oxidative Metabolism during Neonatal Seizures Following Hypoxic-Ischemic Brain Injury. Front Pediatr 2016; 4:83. [PMID: 27559538 PMCID: PMC4978952 DOI: 10.3389/fped.2016.00083] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 07/27/2016] [Indexed: 01/01/2023] Open
Abstract
Seizures are common following hypoxic-ischemic brain injury in newborn infants. Prolonged or recurrent seizures have been shown to exacerbate neuronal damage in the developing brain; however, the precise mechanism is not fully understood. Cytochrome-c-oxidase is responsible for more than 90% of ATP production inside mitochondria. Using a novel broadband near-infrared spectroscopy system, we measured the concentration changes in the oxidation state of cerebral cytochrome-c-oxidase (Δ[oxCCO]) and hemodynamics during recurrent neonatal seizures following hypoxic-ischemic encephalopathy in a newborn infant. A rapid increase in Δ[oxCCO] was noted at the onset of seizures along with a rise in the baseline of amplitude-integrated electroencephalogram. Cerebral oxygenation and cerebral blood volume fell just prior to the seizure onset but recovered rapidly during seizures. Δ[oxCCO] during seizures correlated with changes in mean electroencephalogram voltage indicating an increase in neuronal activation and energy demand. The progressive decline in the Δ[oxCCO] baseline during seizures suggests a progressive decrease of mitochondrial oxidative metabolism.
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Affiliation(s)
- Subhabrata Mitra
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
| | - Gemma Bale
- Department of Medical Physics and Biomedical Engineering, University College London , London , UK
| | - Sean Mathieson
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
| | - Cristina Uria-Avellanal
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
| | - Judith Meek
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
| | - Ilias Tachtsidis
- Department of Medical Physics and Biomedical Engineering, University College London , London , UK
| | - Nicola J Robertson
- Department of Neonatology, Institute for Women's Health, University College London , London , UK
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Mayevsky A, Barbiro-Michaely E. Shedding light on mitochondrial function by real time monitoring of NADH fluorescence: I. Basic methodology and animal studies. J Clin Monit Comput 2012. [PMID: 23203204 DOI: 10.1007/s10877-012-9414-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Normal mitochondrial function in the process of metabolic energy production is a key factor in maintaining cellular activities. Many pathological conditions in animals, as well as in patients, are directly or indirectly related to dysfunction of the mitochondria. Monitoring the mitochondrial activity by measuring the autofluorescence of NADH has been the most practical approach since the 1950s. This review presents the principles and technological aspects, as well as typical results, accumulated in our laboratory since the early 1970s. We were able to apply the fiber-optic-based NADH fluorometry to many organs monitored in vivo under various pathophysiological conditions in animals. These studies were the basis for the development of clinical monitoring devices as presented in accompanying article. The encouraging experimental results in animals stimulated us to apply the same technology in patients after technological adaptations as described in the accompanying article. Our medical device was approved for clinical use by the FDA.
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Affiliation(s)
- Avraham Mayevsky
- The Mina & Everard Goodman Faculty of Life Sciences, Bar-Ilan University, 52900, Ramat Gan, Israel.
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Zhao M, Suh M, Ma H, Perry C, Geneslaw A, Schwartz TH. Focal Increases in Perfusion and Decreases in Hemoglobin Oxygenation Precede Seizure Onset in Spontaneous Human Epilepsy. Epilepsia 2007; 48:2059-67. [PMID: 17666071 DOI: 10.1111/j.1528-1167.2007.01229.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Optical recording of intrinsic signals provides the highest combined spatial and temporal resolution with broad spatial sampling for measuring cerebral blood volume (CBV) and hemoglobin oxygenation in cerebral cortex. Few opportunities arise to apply this laboratory method to record spontaneous seizures in unanesthetized human brain during neurosurgery. We report such a rare opportunity in a man with recurrent focal epilepsy arising from a cavernous malformation. METHODS We recorded intrinsic optical signals (IOS) from human cortex intraoperatively during spontaneous seizures arising from brain surrounding a small cavernous malformation in an awake patient using only local anesthesia with simultaneous electrocorticography. The IOS was recorded at two wavelengths, one an isosbestic point for hemoglobin to measure CBV (570 nm) and the other at a wavelength more sensitive to deoxygenated hemoglobin (Hbr) (610 nm). A modified Beer-Lambert calculation was used on two separate but similar seizures to approximate changes in Hbr, CBV as well as oxygenated hemoglobin (HbO(2)). RESULTS Electrographically recorded seizures (n = 3) elicited a focal increase in both Hbr and CBV that lasted for the duration of the seizure, indicating that perfusion was inadequate to meet metabolic demand. Remarkably, these hemodynamic changes preceded the onset of the seizures by approximately 20 s and occurred focally over the known location of the lesion and the seizure onsets. DISCUSSION These findings demonstrate that the hemoglobin becomes deoxygenated in spite of large increase in CBV during spontaneous human focal seizures and that optically recorded hemodynamic events can be used both to predict and localize human focal epilepsy. Such data may someday be useful to assist in the presurgical evaluation of patients considered for epilepsy surgery and to predict the timing and location of seizure onsets.
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Affiliation(s)
- Mingrui Zhao
- Department of Neurosurgery, Weill Medical College of Cornell University, New York Presbyterian Hospital, 525 East 68th Street, New York, NY 10021, U.S.A
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Mayevsky A, Rogatsky GG. Mitochondrial function in vivo evaluated by NADH fluorescence: from animal models to human studies. Am J Physiol Cell Physiol 2006; 292:C615-40. [PMID: 16943239 DOI: 10.1152/ajpcell.00249.2006] [Citation(s) in RCA: 263] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Normal mitochondrial function is a critical factor in maintaining cellular homeostasis in various organs of the body. Due to the involvement of mitochondrial dysfunction in many pathological states, the real-time in vivo monitoring of the mitochondrial metabolic state is crucially important. This type of monitoring in animal models as well as in patients provides real-time data that can help interpret experimental results or optimize patient treatment. The goals of the present review are the following: 1) to provide an historical overview of NADH fluorescence monitoring and its physiological significance; 2) to present the solid scientific ground underlying NADH fluorescence measurements based on published materials; 3) to provide the reader with basic information on the methodologies used in the past and the current state of the art fluorometers; and 4) to clarify the various factors affecting monitored signals, including artifacts. The large numbers of publications by different groups testify to the valuable information gathered in various experimental conditions. The monitoring of NADH levels in the tissue provides the most important information on the metabolic state of the mitochondria in terms of energy production and intracellular oxygen levels. Although NADH signals are not calibrated in absolute units, their trend monitoring is important for the interpretation of physiological or pathological situations. To understand tissue function better, the multiparametric approach has been developed where NADH serves as the key parameter. The development of new light sources in UV and visible spectra has led to the development of small compact units applicable in clinical conditions for better diagnosis of patients.
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Affiliation(s)
- Avraham Mayevsky
- The Mina & Everard Goodman Faculty of Life Sciences and The Leslie and Susan Gonda Multidisciplinary Brain Research Center, Bar-Ilan Univ., Ramat-Gan 52900, Israel.
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Visioli F, Rihn LL, Rodriguez de Turco EB, Kreisman NR, Bazan NG. Free fatty acid and diacylglycerol accumulation in the rat brain during recurrent seizures is related to cortical oxygenation. J Neurochem 1993; 61:1835-42. [PMID: 8228997 DOI: 10.1111/j.1471-4159.1993.tb09824.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Cerebral blood flow and oxygenation increase during the early seizures of a series, but the increase in cerebral blood flow attenuates during late seizures, sometimes resulting in decreased cortical oxygenation. Cortical free fatty acids (FFA) and diacylglycerols also increase during early seizures and the increase attenuates during late seizures. We analyzed the correlation between lipid accumulation and cortical O2 during periodic pentylenetetrazol-induced seizures. During early seizures, both FFA and diacylglycerols increased in the cerebral cortex, particularly arachidonate (20:4) and stearate (18:0). Changes in lipids were different during late seizures, depending on cortical O2 levels. An increase in cortical O2 during late seizures was associated with lower FFA levels compared with early seizures, and FFA levels recovered to basal levels during interictal periods. A decline in cortical O2 was associated with a further increase in FFA, which remained elevated during interictal periods. Our results indicate that periseizure lipid accumulation is related to cortical oxygenation.
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Affiliation(s)
- F Visioli
- LSU Eye Center and Neuroscience Center, New Orleans 70112
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Hoshi Y, Tamura M. Dynamic changes in cerebral oxygenation in chemically induced seizures in rats: study by near-infrared spectrophotometry. Brain Res 1993; 603:215-21. [PMID: 8384918 DOI: 10.1016/0006-8993(93)91240-s] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Using near-infrared spectrophotometry, the redox state of copper in cytochrome oxidase, and the hemoglobin oxygenation state were measured in the rat brain in situ during and after chemically induced seizures. Pentylentetrazol (PTZ) administration caused the partial reduction of cytochrome oxidase in the brain just before the electroencephalogram (EEG) showed desynchronization, and then blood pressure was elevated concomitantly with an increase in cerebral blood volume. When blood pressure reached a maximum, bursts of spikes appeared on the EEG and cytochrome oxidase was reoxidized to reach the initial oxidation level, giving a rapid, transient reduction of cytochrome oxidase in the preictal period. Hemoglobin was more oxygenated than before the administration throughout the seizure. In the late postictal phase, cytochrome oxidase was partially reduced again, while blood pressure remained high and hemoglobin was more oxygenated than initially. The second administration of PTZ in the late postictal phase induced the same responses as observed after the first administration. By decreasing oxygen concentrations in the inspired gas during the seizure, cytochrome oxidase was more reduced than in the non-epileptic rat, and spike activity was observed until about 85% of cytochrome oxidase was reduced. The transient cerebral hypoxia reflected by the reduction of cytochrome oxidase in the preictal period may be a trigger for an increase in cerebral blood flow rather than the result of a delayed autonomic response. The second reduction of cytochrome oxidase observed in the late postictal phase may be due to a lasting arterio-venous shunt that opens during seizures. These results revive the classical theory that cellular hypoxia is responsible for epileptic brain damage.
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Affiliation(s)
- Y Hoshi
- Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan
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Tomlinson FH, Anderson RE, Meyer FB. Effect of arterial blood pressure and serum glucose on brain intracellular pH, cerebral and cortical blood flow during status epilepticus in the white New Zealand rabbit. Epilepsy Res 1993; 14:123-37. [PMID: 8453950 DOI: 10.1016/0920-1211(93)90017-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Generalized seizures can induce both hypertension and hyperglycemia which may aggravate preexisting cerebral or medical conditions in patients. In vivo fluorescent imaging of regional cortical blood flow and brain intracellular pH (pHi) was performed in fasted New Zealand rabbits (n = 35) in which either mean arterial blood pressure (MABP) or serum glucose was the covaried factor during pentylenetetrazole induced status epilepticus under 1.5% inspired halothane. Baseline brain pHi and regional cortical blood flow were 7.02 +/- 0.02 and 51.1 +/- 1.7 ml/100 g/min, respectively. Following seizure induction, MABP increased to 105 mm Hg and brain pHi fell to 6.79 +/- 0.03 within 15 min and remained at this level for 1 h (P < 0.001). With normalization of MABP during ongoing seizures, there was no worsening in brain pHi despite a significant decrease in regional cortical blood flow. Hyperglycemia decreased pHi to 6.71 +/- 0.02 compared to 6.84 +/- 0.04 in normoglycemic animals (P < 0.001). Using pHi as a cerebral metabolic index, these data suggest that normalization of MABP does not increase metabolic injury while hyperglycemia does significantly worsen brain acidosis. Therefore, administration of glucose to patients with status epilepticus should be avoided unless there is documented hypoglycemia.
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Affiliation(s)
- F H Tomlinson
- Department of Neurosurgery, Mayo Clinic, Rochester, MN 55905
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Kreisman NR, Magee JC, Brizzee BL. Relative hypoperfusion in rat cerebral cortex during recurrent seizures. J Cereb Blood Flow Metab 1991; 11:77-87. [PMID: 1845766 DOI: 10.1038/jcbfm.1991.9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Focal cortical CBF and oxygenation were measured in rats during repetitive seizures to determine whether CBF is maintained above a critical level for adequate delivery of O2. Cerebral oxygenation was determined by measuring relative changes in the oxidation/reduction level of cytochrome aa3 and CBF was measured by the washout of H2. During early seizures, cortical CBF increased to 350% of control and cortical oxygenation also rose markedly. During later seizures, both the increases in CBF and in cortical oxygenation were attenuated progressively. This was accompanied also by attenuation of the associated increases in MABP. Cortical oxygenation decreased during a seizure if the increase in CBF failed to exceed 150-200% of control, defining the critical CBF value. Ventilating the rats on 97% O2 resulted in restoration of the seizure-associated increases in cortical oxygenation in 50% of the cases. The elevation of inspired O2 was effective only if CBF increased once again above 150-200% of control, confirming that the critical CBF lies within this range of values. We conclude that CBF must rise greater than 200% of control levels to provide sufficient O2 to meet the enhanced metabolic requirements of repetitive seizures.
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Affiliation(s)
- N R Kreisman
- Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana 70112
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Abstract
A new approach for the evaluation of brain energy metabolism in awake animals became possible as UV transmitting optical fibers became available. A variety of surface fiber optic fluorometers / reflectometers which were developed during the past decade enabled the monitoring of intramitochondrial NADH redox state in unanesthetized animals. The bundle of flexible fibers was connected to the brain via a cemented light guide holder implanted epidurally. The two signals obtained, 366 nm reflectance and 450 nm fluorescence, are subjected to various artifacts not connected to the intramitochondrial NADH redox state. In our system, the effects of movement artifacts and changes in blood oxygenation are negligible while the effects of tissue absorption or blood volume changes are considerable and could be minimized by subtraction of the two signals (1:1 ratio) providing the corrected fluorescence signal. The brain was exposed to various physiological and pathological conditions which resulted in the increase or decrease in the level of NADH. Under anoxia, hypoxia and ischemia, oxygen availability decreased and the metabolic state of the brain became more reduced (state 4-5 transition). When the brain was activated by seizures, spreading depression of hyperbaric oxygenation NADH became more oxidized (state 4-3 transition).
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LaManna JC, Light AI, Peretsman SJ, Rosenthal M. Oxygen insufficiency during hypoxic hypoxia in rat brain cortex. Brain Res 1984; 293:313-8. [PMID: 6320971 DOI: 10.1016/0006-8993(84)91238-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
To relate cerebral oxygen sufficiency and insufficiency with arterial oxygen tension, reduction/oxidation responses of the initial and terminal members of the mitochondrial respiratory chain (NADH and cytochrome c oxidase) were recorded in situ by optical techniques when increased cerebral energy use was provoked by direct electrical stimulation. Small decreases in paO2, produced by forced ventilation of hypoxic gas mixtures, resulted in decreased amplitude of the characteristic negative shift in extracellular potential which accompanies such stimulation and smaller oxidative response of NADH and cytochrome oxidase. When paO2 fell below 40-50 Torr, stimulation produced reductive rather than oxidative shifts of the mitochondrial respiratory chain components. The data suggest that when arterial oxygen tension is slightly decreased, compensating mechanisms allow brain function to continue with minimal changes in cortical metabolites and high energy phosphate compounds. When arterial oxygen falls below 40-50 Torr, however, compensation can no longer prevent tissue hypoxia during times of increased energy demand. Thus, hypoxemia is not necessarily synonymous with oxygen insufficiency, but oxygen sufficiency must be defined with due regard to the degree of energy demand.
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Kreisman NR, Sick TJ, Rosenthal M. Concepts of brain oxygen sufficiency during seizures. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1984; 180:381-92. [PMID: 6099961 DOI: 10.1007/978-1-4684-4895-5_36] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
To resolve conflicting evidence of oxygen sufficiency or insufficiency during seizures, signals of metabolic and circulatory function were monitored in rat cerebral cortex during recurrent seizures. Early seizures were accompanied by increased blood volume, increased tPO2, and oxidative shifts of cytochrome a,a3, indicative of oxygen sufficiency. Later seizures were accompanied by a smaller increment in blood volume, a fall in tPO2, and shifts toward reduction of cytochrome a,a3, suggesting that cerebral oxygen supply became insufficient to meet demand. Responses suggesting oxygen insufficiency occurred during short duration ictal bursts, interictal spikes or electrocortical stimulation at times when longer duration ictal episodes still were accompanied by responses signalling oxygen sufficiency. These data indicate that there is a progressive dissociation of the normally tight couple between neuronal activity, energy demand, and cerebral blood flow during status epilepticus. Systemic derrangements that often accompanied recurrent seizures also contributed to decreased cerebral oxygenation. These factors may cause the neuronal damage reported to follow prolonged status epilepticus.
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Abstract
The cerebral metabolic state was studied in cats during insulin-induced hypoglycemia and the recovery after glucose infusion. Changes in the redox state of nicotinamide adenine dinucleotide (NAD) were monitored from the surface of the exposed cerebral cortex using microfluorometry. After insulin injection blood glucose fell from 6.85 mumol/ml to 0.45 mumol/ml at EEG isoelectricity and was accompanied by an oxidation of NADH+. Upon intravenous glucose infusion EEG activity rapidly returned and NAD became more reduced. The oxidation of NADH+ during severe hypoglycemia demonstrated that the in vivo redox state of mitochondria behave in a similar manner as isolated mitochondria when reducing equivalents become limiting to the respiratory chain.
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Abstract
The rate of cortical gamma-aminobutyric acid (GABA) turnover was estimated by determining the rate of GABA accumulation following inhibition of GABA transaminase by gamma-vinyl-GABA (1.5 g/kg, i.v.) in paralysed, ventilated rats. During 1 h of bicuculline-induced seizures (1.2 mg/kg, i.v.) the rate of accumulation of cortical GABA level is approximately threefold greater than in the control group receiving gamma-vinyl-GABA alone, suggesting that the GABA shunt activity increases in parallel with the increase in overall cortical metabolic rate observed during bicuculline seizures. Pretreatment with gamma-vinyl-GABA did not affect the bicuculline-induced changes in other major cortical amino acids.
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Kreisman NR, Sick TJ, Rosenthal M. Importance of vascular responses in determining cortical oxygenation during recurrent paroxysmal events of varying duration and frequency of repetition. J Cereb Blood Flow Metab 1983; 3:330-8. [PMID: 6874742 DOI: 10.1038/jcbfm.1983.48] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Cerebral oxygenation initially increases and later decreases in rats subjected to experimental status epilepticus. In this study, we have compared cerebral oxygen supply and vascular changes during paroxysmal events of different durations and at different time intervals to test the hypothesis that oxygen insufficiency is associated more readily with paroxysmal events of greater intensity. Continuous measurements were made of local changes in cortical blood volume, redox levels of cytochrome a, a3, cortical Po2, and systemic arterial blood pressure during recurrent seizures induced by pentylenetetrazol or bicuculline. In contrast to expectations, systemic and cerebral vascular responses and associated increases in cerebral oxygenation were better maintained during long-duration ictal episodes than during short-duration ictal bursts, interictal spikes, or evoked potentials. Short-duration paroxysmal events were often accompanied by decreases in cerebral oxygenation, whereas long-duration events were still accompanied by increases in oxygenation. Ictal bursts occurring with short interburst intervals caused a more rapid failure of vascular responsiveness than those occurring at longer intervals. These relationships of intensity and frequency of repetition of seizures to changes in vascular responses indicate progressive dissociation of the normally tight couple between neuronal activity, energy demand, and cerebral blood flow during status epilepticus.
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Kreisman NR, Lamanna JC, Rosenthal M, Sick TJ. Oxidative metabolic responses with recurrent seizures in rat cerebral cortex: role of systemic factors. Brain Res 1981; 218:175-88. [PMID: 6268244 DOI: 10.1016/0006-8993(81)91299-3] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Simultaneous focal measurements of cerebral oxygen tension and cytochrome a,a3 redox levels were made in rat cortex in order to obtain a direct and continuous assessment of oxidative metabolic changes during serial seizures. Initial seizures evoked by pentylenetetrazol were accompanied by transient increases in tissue pO2 and cytochrome a,a3 oxidation, confirming that oxygen provision is adequate to meet metabolic demand. After some point, subsequent seizures were accompanied by failure of pO2 to increase and failure of cytochrome a,a3 to oxidize, or by decreases in tissue pO2 and shifts in the redox level of cytochrome a,a3 toward reduction, signalling cortical oxygen insufficiency. Whereas early seizures were accompanied by increments in both cerebral blood volume and arterial blood pressure, one or both of these variables failed to increment during later seizures. This was particularly evident following the onset of spontaneously recurring seizures with short intervals between bursts of ECoG activity. These investigations emphasize the importance of systemic factors in determining the cerebral metabolic response to seizures and support the suggestion that neuronal damage in status epilepticus may be the result of derangements of oxidative metabolism.
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Vern BA, Schuette WH, Whitehouse WC. Effects of brain stem stimulation on cortical NADH fluorescence, blood flow, and O2 consumption in the cat. Exp Neurol 1981; 71:581-600. [PMID: 7461081 DOI: 10.1016/0014-4886(81)90034-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Tenny RT, Sharbrough FW, Anderson RE, Sundt TM. Correlation of intracellular redox states and pH with blood flow in primary and secondary seizure foci. Ann Neurol 1980; 8:564-73. [PMID: 6782936 DOI: 10.1002/ana.410080604] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Epileptogenic foci were created by topical application of penicillin to the cerebral cortex in 40 paralyzed and artificially ventilated cats receiving halothane anesthesia. The animals were divided into two equal groups to compare primary and secondary foci. The following variables were recorded at normocapnia, hypocapnia, and hypercapnia prior to and during seizure activity: cerebral blood flow (CBF), determined by clearance of xenon 133; cortical redox states, measured by the fluorescence of reduced pyridine nucleotides (PN); brain pH, measured using a lipid-soluble, pH-sensitive fluorescent indicator; and electroencephalograms (EEG). Mean arterial blood pressure, arterial pH, arterial carbon dioxide tension (PaCO2), and arterial oxygen tension (PaO2) were monitored in each animal. All animals had a normal PaCO2-CBF response prior to the creation of a seizure focus, assuring the presence of autoregulation and normal metabolic function. CBF increased equally with seizures in the primary and secondary hemispheres. The relative increase was related to the PaCO2 but approximated 68% at normocapnia. There was an alteration in the PaCO2-CBF response with seizures, but the ability of the cerebral vasculature to constrict and dilate with hypocapnia and hypercapnia was retained. There was no significant difference in the reduced PN signal with variations in PaCO2 prior to seizures, but there was an apparent 10 to 15% fall with seizures. The "equivalent" intracellular pH fell to 6.94 at normocapnia in the primary focus but remained essentially unchanged from the control value of 7.10 in the secondary focus. These differences in pH were consistent with the greater degree of seizure activity observed in the primary focus. We conclude that a nonhypoxic acidosis existed in the primary focus and that changes in CBF were not related to it because the CBF changed equally in both hemispheres.
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Vern BA, Schuette WH, Mutsuga N, Whitehouse WC. Effects of ischemia on the removal of extracellular potassium in cat cortex during pentylenetetrazol seizures. Epilepsia 1979; 20:711-24. [PMID: 227667 DOI: 10.1111/j.1528-1157.1979.tb04855.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Changes in cortical extracellular potassium activity ([K+]0), NADH fluorescence, and oxygen consumption were studied in anesthetized cats during pentylenetetrazol seizures. The effects of partial ischemia induced by either hypotension or intermittent carotid artery occlusion on these parameters were investigated. Nonischemic seizures were characterized by gradual generalized decreases in cortical NADH fluorescence and increases in O2 consumption, along with rapid increases in [K+]0, which then usually fell slightly as the ictal discharge continued. Ischemic seizures, on the other hand, were accompanied by complex changes in NADH fluorescence, by smaller delayed maximal increases in O2 consumption that lasted beyond the end of ictal activity, and by more sustained increases in [K+]0. The decay of [K+]0 after the termination of seizures in both nonischemic and moderately ischemic animals was not a monoexponential function: plots of ln delta [K+]0 versus time showed an initial linear decline (of slope M1) that rather abruptly slowed (to slope M2) after 2 to 5 sec and then often increased to the original rate. Both M1 and M2 were proportionately decreased by ischemia. In addition, the rate of [K+]0 removal could be slowed by acute ischemia induced either during or after the end of ictal activity. The initial rate of postictal [K+]0 removal (M1) was found to be linearly and inversely related to the level of cortical NADH fluorescence at the time of seizure termination. The results of this study suggest that an O2-dependent transport mechanism plays a major role in the removal of [K+]0 during and following the termination of generalized pentylenetetrazol seizures in the cat.
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