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How to Improve the Antioxidant Defense in Asphyxiated Newborns-Lessons from Animal Models. Antioxidants (Basel) 2020; 9:antiox9090898. [PMID: 32967335 PMCID: PMC7554981 DOI: 10.3390/antiox9090898] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 09/12/2020] [Accepted: 09/15/2020] [Indexed: 02/07/2023] Open
Abstract
Oxygen free radicals have been implicated in brain damage after neonatal asphyxia. In the early phase of asphyxia/reoxygenation, changes in antioxidant enzyme activity play a pivotal role in switching on and off the cascade of events that can kill the neurons. Hypoxia/ischemia (H/I) forces the brain to activate endogenous mechanisms (e.g., antioxidant enzymes) to compensate for the lost or broken neural circuits. It is important to evaluate therapies to enhance the self-protective capacity of the brain. In animal models, decreased body temperature during neonatal asphyxia has been shown to increase cerebral antioxidant capacity. However, in preterm or severely asphyxiated newborns this therapy, rather than beneficial seems to be harmful. Thus, seeking new therapeutic approaches to prevent anoxia-induced complications is crucial. Pharmacotherapy with deferoxamine (DFO) is commonly recognized as a beneficial regimen for H/I insult. DFO, via iron chelation, reduces oxidative stress. It also assures an optimal antioxidant protection minimizing depletion of the antioxidant enzymes as well as low molecular antioxidants. In the present review, some aspects of recently acquired insight into the therapeutic effects of hypothermia and DFO in promoting neuronal survival after H/I are discussed.
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Kletkiewicz H, Hyjek M, Jaworski K, Nowakowska A, Rogalska J. Activation of hypoxia-inducible factor-1α in rat brain after perinatal anoxia: role of body temperature. Int J Hyperthermia 2017; 34:824-833. [DOI: 10.1080/02656736.2017.1385860] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Affiliation(s)
- Hanna Kletkiewicz
- Department of Animal Physiology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Toruń, Poland
| | - Malwina Hyjek
- Department of Cell Biology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Toruń, Poland
- Centre For Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Toruń, Poland
| | - Krzysztof Jaworski
- Chair of Plant Physiology and Biotechnology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Toruń, Poland
| | - Anna Nowakowska
- Department of Animal Physiology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Toruń, Poland
| | - Justyna Rogalska
- Department of Animal Physiology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Toruń, Poland
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Deferoxamine improves antioxidative protection in the brain of neonatal rats: The role of anoxia and body temperature. Neurosci Lett 2016; 628:116-22. [PMID: 27297770 DOI: 10.1016/j.neulet.2016.06.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 06/08/2016] [Accepted: 06/09/2016] [Indexed: 01/24/2023]
Abstract
After hypoxic-ischemic insult iron deposited in the brain catalyzes formation of reactive oxygen species. Newborn rats, showing reduced physiological body temperature and their hyperthermic counterparts injected with deferoxamine (DF), a chelator of iron, are protected both against iron-mediated neurotoxicity and against depletion of low-molecular antioxidants after perinatal asphyxia. Therefore, we decided to study the effects of DF on activity of antioxidant enzymes (superoxide dismutase-SOD, glutathione peroxidase-GPx and catalase-CAT) in the brain of rats exposed neonatally to a critical anoxia at body temperatures elevated to 39°C. Perinatal anoxia under hyperthermic conditions intensified oxidative stress and depleted the pool of antioxidant enzymes. Both the depletion of antioxidants and lipid peroxidation were prevented by post-anoxic DF injection. The present paper evidenced that deferoxamine may act by recovering of SOD, GPx and CAT activity to reduce anoxia-induced oxidative stress.
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Kletkiewicz H, Nowakowska A, Siejka A, Mila-Kierzenkowska C, Woźniak A, Caputa M, Rogalska J. Deferoxamine prevents cerebral glutathione and vitamin E depletions in asphyxiated neonatal rats: role of body temperature. Int J Hyperthermia 2016; 32:211-20. [PMID: 26794834 DOI: 10.3109/02656736.2015.1125955] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Hypoxic-ischaemic brain injury involves increased oxidative stress. In asphyxiated newborns iron deposited in the brain catalyses formation of reactive oxygen species. Glutathione (GSH) and vitamin E are key factors protecting cells against such agents. Our previous investigation has demonstrated that newborn rats, showing physiological low body temperature as well as their hyperthermic counterparts injected with deferoxamine (DF) are protected against iron-mediated, delayed neurotoxicity of perinatal asphyxia. Therefore, we decided to study the effects of body temperature and DF on the antioxidant status of the brain in rats exposed neonatally to critical anoxia. Two-day-old newborn rats were exposed to anoxia in 100% nitrogen atmosphere for 10 min. Rectal temperature was kept at 33 °C (physiological to rat neonates), or elevated to the level typical of healthy adult rats (37 °C), or of febrile adult rats (39 °C). Half of the rats exposed to anoxia under extremely hyperthermic conditions (39 °C) were injected with DF. Cerebral concentrations of malondialdehyde (MDA, lipid peroxidation marker) and the levels of GSH and vitamin E were determined post-mortem, (1) immediately after anoxia, (2) 3 days, (3) 7 days, and (4) 2 weeks after anoxia. There were no post-anoxic changes in MDA, GSH and vitamin E concentrations in newborn rats kept at body temperature of 33 °C. In contrast, perinatal anoxia at elevated body temperatures intensified oxidative stress and depleted the antioxidant pool in a temperature-dependent manner. Both the depletion of antioxidants and lipid peroxidation were prevented by post-anoxic DF injection. The data support the idea that hyperthermia may extend perinatal anoxia-induced brain lesions.
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Affiliation(s)
- Hanna Kletkiewicz
- a N. Copernicus University , Department of Animal Physiology, Faculty of Biology and Environmental Protection , Toruń , Poland and
| | - Anna Nowakowska
- a N. Copernicus University , Department of Animal Physiology, Faculty of Biology and Environmental Protection , Toruń , Poland and
| | - Agnieszka Siejka
- a N. Copernicus University , Department of Animal Physiology, Faculty of Biology and Environmental Protection , Toruń , Poland and
| | | | - Alina Woźniak
- b N. Copernicus University , Department of Medical Biology, Collegium Medicum , Bydgoszcz , Poland
| | - Michał Caputa
- a N. Copernicus University , Department of Animal Physiology, Faculty of Biology and Environmental Protection , Toruń , Poland and
| | - Justyna Rogalska
- a N. Copernicus University , Department of Animal Physiology, Faculty of Biology and Environmental Protection , Toruń , Poland and
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5
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Rogalska J, Caputa M. Neonatal asphyxia under hyperthermic conditions alters HPA axis function in juvenile rats. Neurosci Lett 2010; 472:68-72. [DOI: 10.1016/j.neulet.2010.01.060] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 01/18/2010] [Accepted: 01/26/2010] [Indexed: 10/19/2022]
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6
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Rogalska J. Mineralocorticoid and glucocorticoid receptors in hippocampus: their impact on neurons survival and behavioral impairment after neonatal brain injury. VITAMINS AND HORMONES 2010; 82:391-419. [PMID: 20472149 DOI: 10.1016/s0083-6729(10)82020-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Glucocorticoids (GC) exert multiple effects within the central nervous system via mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) activation. MR expression is associated with a neuroprotective phenotype, whereas GR activation is implicated in the induction of an endangered neural phenotype and the opposite actions are most evident in hippocampus, where these receptors are predominantly present. Hippocampus has an overall inhibitory influence on the activity of the hypothalamic-pituitary-adrenal (HPA) axis and it has been suggested that efficient learning and adequate stress response depend on the appropriate functioning of the axis brought by coordinated activation of MR and GR in this region. There is a growing body of evidence that perinatal asphyxia causes irreversible damage to the brain leading to neurons loss in regions vulnerable to oxygen shortage especially in hippocampus. In the present review, some aspects of recently acquired insight in the role of GC receptors in promoting neuronal death and survival after hippocampal injury are discussed. Since the unbalance of MR and GR in hippocampus creates a condition of disturbed neuroendocrine regulation their potential impact on behavioral impairment will also be reviewed.
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Affiliation(s)
- Justyna Rogalska
- Department of Animal Physiology, Institute of General and Molecular Biology, N. Copernicus University, Torun, Poland
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Rogalska J, Caputa M, Piątkowska K, Nowakowska A. Neonatal asphyxia and hyperthermia and cognitive deficits in adult rats: Role of iron. J Therm Biol 2009. [DOI: 10.1016/j.jtherbio.2009.08.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Kang P, Rogalska J, Walker CA, Burke M, Seckl JR, Macleod MR, Lai M. Injury-induced mineralocorticoid receptor expression involves differential promoter usage: a novel role for the rat MRbeta variant. Mol Cell Endocrinol 2009; 305:56-62. [PMID: 19433261 DOI: 10.1016/j.mce.2009.02.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/03/2009] [Accepted: 02/12/2009] [Indexed: 11/20/2022]
Abstract
Neuronal injury results in increased mineralocorticoid receptor (MR) expression and is associated with increased neuronal survival, suggesting that enhancing MR signalling may have therapeutic implications. MR has a complex gene structure with at least three untranslated exons (alpha, beta, gamma) each with unique promoters and a common coding region. We examined whether distinct cellular stressors differentially regulate exon-specific MR transcripts. MRbeta transcript was specifically upregulated in rat primary cortical cultures undergoing hypothermic oxygen-glucose deprivation (OGD/H) through activation of its own promoter. This effect was mediated in part by ERK signalling as blockade with PD98059 inhibited OGD/H-induced MRbeta promoter activity. A specific increase in MRbeta transcript expression was also found in vivo in hypothermic anoxic neonatal rat hippocampus. These results demonstrate a novel key role for the MRbeta transcript in response to injury and suggest that some of the known neuroprotective effects of hypothermia may be mediated through increased MR expression.
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Affiliation(s)
- Peng Kang
- Endocrinology Unit, Centre for Cardiovascular Science, University of Edinburgh, Scotland, UK
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9
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Rogalska J, Kang P, Wotherspoon W, Macleod MR, Lai M. Effect of hyperthermia and anoxia on glucocorticoid and mineralocorticoid receptor expression in neonatal rat hippocampus. Neurosci Lett 2008; 450:196-200. [PMID: 19028552 DOI: 10.1016/j.neulet.2008.11.033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2008] [Revised: 11/07/2008] [Accepted: 11/13/2008] [Indexed: 01/17/2023]
Abstract
Brief periods of neonatal asphyxia are frequently observed. Within the CNS, the hippocampus is known to be particularly vulnerable to the damaging effects of hypoxia/ischaemia. The hippocampus contains the highest concentration of both mineralocorticoid (MR) and glucocorticoid (GR) receptors and the balance between MR/GR activation influences cell birth and death. MR occupation appears to promote prosurvival actions, while GR overactivation favours neurodegeneration. It has been widely recognized that core body temperature is a critical determinant of the severity of hypoxic-ischemic brain injury; indeed, hyperthermia exacerbates the degree of damage. Therefore, the aim of the present investigation was to study the effect of elevated body temperature in newborn rats under control conditions or during neonatal exposure to a critical anoxia, on changes of MR and GR mRNA expression in the rat hippocampus. 2-day-old rats were exposed to anoxia in 100% nitrogen atmosphere. Rectal temperature was kept at 33 degrees C (typical for the rat neonates), or elevated to a level typical for febrile (39 degrees C) adults. Control rats were exposed to atmospheric air under the respective thermal conditions. The changes in MR and GR mRNA expression in hippocampus were examined 24h after exposure. Our data show that hyperthermia with or without added anoxia, causes induction of MR mRNA expression in neonatal rat hippocampus without any effect on GR mRNA expression. We suggest this elevation of MR plays an important role in modulating the survival of neurons in the injured hippocampus.
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Affiliation(s)
- Justyna Rogalska
- Department of Animal Physiology, Institute of General and Molecular Biology, N. Copernicus University, ul. Gagarina 9, 87-100 Toruń, Poland.
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Howes D, Green R, Gray S, Stenstrom R, Easton D. Evidence for the use of hypothermia after cardiac arrest. CAN J EMERG MED 2007; 8:109-15. [PMID: 17175872 DOI: 10.1017/s1481803500013579] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Daniel Howes
- Emergency Medicine and Critical Care, Queen's University, Kingston, ON.
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11
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Hypothermie après un arrêt cardiaque. CAN J EMERG MED 2006. [DOI: 10.1017/s1481803500013580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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12
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Rogalska J, Danielisova V, Caputa M. Effect of neonatal body temperature on postanoxic, potentially neurotoxic iron accumulation in the rat brain. Neurosci Lett 2006; 393:249-54. [PMID: 16289321 DOI: 10.1016/j.neulet.2005.09.085] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Revised: 09/13/2005] [Accepted: 09/29/2005] [Indexed: 10/25/2022]
Abstract
In asphyxiated newborns iron, released from heme and ferritin and deposited in the brain, contributes to neurodegeneration. Because hypothermia provides neuroprotection, newborn mammals, showing spontaneously reduced body temperature, might avoid the iron-mediated neurotoxicity. Therefore, we decided to study the effects of body temperature and chelation of iron with deferoxamine on iron accumulation in the brain of three weeks old rats exposed neonatally to a critical anoxia. At the age of two days, newborn rats were exposed to anoxia in 100% nitrogen atmosphere. Rectal temperature was kept at 33 degrees C (typical of the rat neonates), or elevated to a level typical of febrile (39 degrees C) adults. Control rats were exposed to atmospheric air in the respective thermal conditions. Half of the rats exposed to anoxia under hyperthermic conditions were injected with deferoxamine (DF), immediately after anoxia and 24 h later. Regional changes in cerebral iron deposition were examined in the frontal cortex, the hippocampus and the striatum, using iron histochemistry, when the rats reached the age of three weeks. Increased iron staining was found in neurons of each of the three cerebral regions in rats exposed to neonatal anoxia under hyperthermic conditions and the iron accumulation was prevented by postanoxic DF injection. In conclusion, febrile body temperature amplifies cerebral hyperferremia, which might induce neurodegenerative disturbances in the brain. On the other hand, a protection against the brain hyperferremia can be achieved by both the reduced physiological neonatal body temperature and by postasphyxic DF administration.
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Affiliation(s)
- Justyna Rogalska
- Department of Animal Physiology, Institute of General and Molecular Biology, N. Copernicus University, ul. Gagarina 9, 87-100 Toruń, Poland.
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Caputa M, Rogalska J, Wentowska K, Nowakowska A. Perinatal asphyxia, hyperthermia and hyperferremia as factors inducing behavioural disturbances in adulthood: A rat model. Behav Brain Res 2005; 163:246-56. [PMID: 16038989 DOI: 10.1016/j.bbr.2005.05.015] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Revised: 05/16/2005] [Accepted: 05/19/2005] [Indexed: 11/19/2022]
Abstract
Alertness was studied in adult male Wistar rats after neonatal critical anoxia applied under three different thermal conditions: (i) at physiological neonatal body temperature of 33 degrees C, (ii) at body temperature elevated to 37 degrees C, and (iii) at body temperature elevated to 39 degrees C (both during anoxia and for 2 h postanoxia). To elucidate the effect of iron-dependent postanoxic oxidative damage to the brain, half of the group (iii) was injected with deferoxamine, a chelator of iron. Postanoxic behavioural disturbances were recorded in open-field, elevated plus-maze, and sudden silence tests when the rats reached the age of 4 month. Moreover, spontaneous motor activity of the rats was recorded radiotelemetrically in their home-cages. Both open-field stress-induced and spontaneous motor activity were reduced in rats subjected to neonatal anoxia under hyperthermic conditions. In contrast, these rats were hyperactive in the plus-maze test. Both the plus-maze and sudden silence tests revealed that these rats show reduced alertness to external stimuli signalling potential dangers. The behavioural disturbances were prevented by the body temperature of 33 degrees C and by postanoxic administration of deferoxamine. These data support the conclusion that permanent postanoxic behavioural disturbances are due to iron-dependent oxidative damage to the brain, which can be prevented by the reduced neonatal body temperature.
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Affiliation(s)
- Michał Caputa
- Department of Animal Physiology, Institute of General and Molecular Biology, N. Copernicus University, Toruń, Poland.
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Spontaneously reduced body temperature and gasping ability as a mechanism of extreme tolerance to asphyxia in neonatal rats. J Therm Biol 2005. [DOI: 10.1016/j.jtherbio.2005.02.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Bohr I. Hypercholesterolemic diet applied to rat dams protects their offspring against cognitive deficits. Simulated neonatal anoxia model. Physiol Behav 2004; 82:703-11. [PMID: 15327920 DOI: 10.1016/j.physbeh.2004.06.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2003] [Revised: 06/09/2004] [Accepted: 06/10/2004] [Indexed: 11/29/2022]
Abstract
There is accumulating data suggesting a neuroprotective activity of cholesterol, especially in stroke and Alzheimer's disease (AD). In the present study, a protective activity of this lipid in simulated neonatal anoxia was investigated. Rats were subjected to high cholesterol by feeding their dams with a diet enriched with cholesterol. Half of these rats were subjected to anoxia. One and a half months later, the rats were tested for their ability to acquire a spatial memory, one group on the linear maze and the other on the Morris water maze. After these assessments, the level of total plasma cholesterol was measured. Rats from dams subjected to neonatal anoxia on standard diet performed worse than control rats in both types of behavioral experiments, whereas anoxic rats from dams were housed on hypercholesterolemic diet performed as control animals. It suggests that dietetic cholesterol applied by their dams protected rats against cognitive deficits elicited by neonatal anoxia. Furthermore, offspring of anoxic rats housed on standard diet had elevated levels of blood cholesterol in relation to control animals. Generally, anoxia affected the concentration of this lipid much stronger than hypercholesterolemic diet of their dams. It might mean that the anoxia-related rise of cholesterol could be involved in physiological phenomenon being an adaptive response to neurotoxic processes. This concept is discussed in relation to pathological mechanisms in AD.
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Affiliation(s)
- Iwo Bohr
- Department of Animal Physiology, Institute of General and Molecular Biology, Nicholas Copernicus University, ul. Gagarina 9, 87-100 Torun, Poland.
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Rogalska J, Caputa M, Wentowska K, Nowakowska A. Stress-induced behaviour in juvenile rats: effects of neonatal asphyxia, body temperature and chelation of iron. Behav Brain Res 2004; 154:321-9. [PMID: 15313019 DOI: 10.1016/j.bbr.2004.02.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2003] [Revised: 02/20/2004] [Accepted: 02/25/2004] [Indexed: 10/26/2022]
Abstract
Newborn mammals, showing reduced normal body temperature, might be protected against iron-mediated, delayed neurotoxicity of perinatal asphyxia. Therefore, we investigated the effects of (1) neonatal body temperature and neonatal critical anoxia as well as (2) postanoxic chelation of iron with deferoxamine, on open-field stress-induced behaviour in juvenile rats. The third aim of this study was to compare (after the above-mentioned treatments) circadian changes in spontaneous motor activity and body temperature in juvenile rats permanently protected from any stress. Neonatal anoxia at body temperature adjusted (both during anoxia and 2 h reoxygenation) to a level typical of healthy (37 degrees C) or febrile (39 degrees C) adults led to the stress-induced hyperactivity in juvenile (5-45 days old) rats. Both normal neonatal body temperature of 33 degrees C and chelation of iron prevented the hyperactivity in rats. Neither neonatal body temperature nor neonatal anoxia affected spontaneous motor activity or body temperature of juvenile rats, recorded in their home-cages with implantable transmitters. Circadian rhythmicity was also undisturbed. Presented data support the hypothesis that physiologically reduced neonatal body temperature can provide a protection against iron-mediated postanoxic disturbances of behavioural stress responses in juvenile rats.
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Affiliation(s)
- Justyna Rogalska
- Department of Animal Physiology, Institute of General and Molecular Biology, N. Copernicus University, ul. Gagarina 9, 87-100 Toruń, Poland.
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Oakden E, Chiswick M, Rothwell N, Loddick S. The influence of litter size on brain damage caused by hypoxic-ischemic injury in the neonatal rat. Pediatr Res 2002; 52:692-6. [PMID: 12409515 DOI: 10.1203/00006450-200211000-00014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Hypoxic ischemia is a common cause of brain injury in the human neonate. This can be mimicked in the neonatal rat, but produces variable injury. The present study investigated the influence of litter size on the severity and variability of damage caused by hypoxic-ischemic injury in neonatal rats. Groups of 7-d-old pups from birth-sized litters (13-15 pups), or from litters culled to 10 on postnatal d 2, and 8- and 9-d-old pups from birth-sized litters, were exposed to common carotid artery occlusion and then, 3 h later, hypoxia (2 h 15 min, 8% oxygen). Damage was assessed histologically 72 h after injury, and graded (I-IV) according to severity. In nonculled litters, similar numbers of animals had each grade of injury. Most pups (70%) from culled litters had grade III or IV damage, and severity was significantly greater than in nonculled litters (p < 0.001). Pups from culled litters were heavier (17.6 +/- 0.4 g) than pups from nonculled litters (14.7 +/- 0.3 g, p < 0.0001). To determine whether this indicated that culled litters were more similar to older pups in their response to hypoxic-ischemic injury, we examined injury in 8- and 9-d-old pups of similar body weight to 7-d-old pups from culled litters. The severity and distribution of damage in the older pups was different from damage in the 7-d-old pups from culled litters. These data suggest that in 7-d-old rats, litter size influences damage caused by hypoxic-ischemic injury, and that the relationship between body weight, brain development, and susceptibility to hypoxic-ischemic injury is complex.
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Affiliation(s)
- Elizabeth Oakden
- School of Biological Sciences, University of Manchester, Manchester, UK
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