Neonatal Anoxia Impacts Rats' Maternal Behavior and Offspring Development due to Ultrasonic Vocalization's Impairment.

Hypoxic-ischemic encephalopathy is a severe clinical condition, among others, affecting the brain after offspring exposure to neonatal anoxia, which causes persistent sensorimotor and cognitive deficits. During peripartum, maternal behaviors are crucial for the healthy development of the offspring. In rats, the vocalization of newborns, around 40 kHz, corresponds to separation calls that encourage their mothers to retrieve them. Alterations in this pattern affect the maternal behavior addressed to the offspring. This study aimed to evaluate the maternal behavior of primiparous rats whose offspring were exposed to neonatal anoxia in P2 (postpartum day) during the lactation period, to assess mother-pup interactions through the pups' vocalization from P3 to P18. It also intends to quantify eventual neuronal alterations in the mothers' medial preoptic area after the last weaning (P21) through FOS protein expression. Anoxia offspring were found to reduce maternal behaviors toward them, increased frequency of separation calls in the male anoxia group, and reduced vocalization rate in the female anoxia group compared to their respective controls. Body weight gain reduction of males' and females' anoxia was observed. We concluded that anoxia exerts deleterious effects on the vocalization patterns of the pups, with sex differences that alter maternal behavior toward them. Impaired USV makes an additional negative impact on the already noxious effects of neonatal anoxia. Understanding those phenomena applies/contributes to guiding procedures and strategies to mitigate the deleterious outcomes and orient research concerning the complexity of neonatal anoxia events and the influence of maternal care quality concerning the pups, which should also be considered sex differences.

Deferoxamine prevents cerebral glutathione and vitamin E depletions in asphyxiated neonatal rats: role of body temperature.

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.

Indole-3-carbinol ameliorated the neurodevelopmental deficits in neonatal anoxic injury in rats.

Neonatal anoxia is linked to long-lasting neurodevelopmental deficits. Due to the lack of pharmacological intervention to treat neonatal anoxia, there is interest in finding new molecules for its treatment. Indole-3-carbinol (I3C) has shown neuroprotective effects in some disease conditions. However, the neuroprotective role of I3C in neonatal anoxia has not been explored. Consequently, we have investigated the effect of I3C on neonatal anoxia-induced brain injury and neurodevelopmental deficits. Rat pups after 30 h of birth were subjected to two episodes of anoxia (10 min in each) at a time interval of 24 h by flowing 100% nitrogen. I3C was administered within 30 min of the second episode of anoxia on a postnatal day (PND) 3 and continued for PND 9. Neurodevelopmental deficits, cortical mitochondrial membrane potential (MMP), opening of mitochondrial permeability transition pore (MPTP), electron transport chain (ETC) enzyme activities, oxidative stress, hypoxia-inducible factor-1α (HIF-1α) levels, histopathological changes, and apoptosis were measured. I3C treatment dose-dependently ameliorated the neurodevelopmental deficits and somatic growth in anoxic pups. I3C improved mitochondrial function by enhancing the MMP, mitochondrial ETC enzymes, and antioxidants. It blocked the MPTP opening and release of cytochrome C in anoxic pups. Further, I3C reduced the elevated cortical HIF-1α in neonatal anoxic pups. Furthermore, I3C ameliorated histopathological abnormalities and mitochondrial-mediated apoptotic indicators Cyt C, caspase-9, and caspase-3. Our study concludes that I3C improved neuronal development in anoxic pups by enhancing mitochondrial function, reducing HIF-1α, and mitigating apoptosis.

Neonatal anoxia increases nociceptive response in rats: Sex differences and lumbar spinal cord and insula alterations.

Neonatal anoxia is a well-known world health problem that results in neurodevelopmental deficits, such as sensory alterations that are observed in patients with cerebral palsy and autism disorder, for which oxygen deprivation is a risk factor. Nociceptive response, as part of the sensory system, has been reported as altered in these patients. To determine whether neonatal oxygen deprivation alters nociceptive sensitivity and promotes medium- and long-term inflammatory feedback in the central nervous system, Wistar rats of around 30 h old were submitted to anoxia (100% nitrogen flux for 25 min) and evaluated on PND23 (postpartum day) and PND90. The nociceptive response was assessed by mechanical, thermal, and tactile tests in the early postnatal and adulthood periods. The lumbar spinal cord (SC, L4-L6) motor neurons (MNs) and the posterior insular cortex neurons were counted and compared with their respective controls after anoxia. In addition, we evaluated the possible effect of anoxia on the expression of astrocytes in the SC at adulthood. The results showed increased nociceptive responses in both males and females submitted to anoxia, although these responses were different according to the nociceptive stimulus. A decrease in MNs in adult anoxiated females and an upregulation of GFAP expression in the SC were observed. In the insular cortex, a decrease in the number of cells of anoxiated males was observed in the neonatal period. Our findings suggest that oxygen-deprived nervous systems in rats may affect their response at the sensorimotor pathways and respective controlling centers with sex differences, which were related to the used stimulus.

Spontaneous umbilical cord hematoma with a favorable outcome.

Umbilical cord hematoma is a rare but serious complication of pregnancy or childbirth that often results in neonatal hypoxia-ischemia and death. We describe a newborn infant with spontaneous umbilical cord hematoma, resulting in transient hypoxia-ischemia. Treatment with therapeutic hypothermia was rapidly initiated by a multidisciplinary team of obstetricians, midwives, and neonatologists. Risk factors for umbilical cord hematoma reported in the literature were investigated. The neurological signs, electroencephalogram, and blood analysis results improved rapidly. This case report demonstrates that the effective management of anoxia-ischemia caused by umbilical cord hematoma can lead to a positive outcome for the newborn infant.

Impairment of nociceptive responses after neonatal anoxia correlates with somatosensory thalamic damage: A study in rats.

Chronic neuropathic pain resulting from damage to the central or peripheral nervous system is a prevalent and debilitating condition affecting 7-18% of the population. Symptoms include spontaneous pain, dysesthesia, paresthesia, allodynia and hyperalgesia. The reported sensory symptoms are comorbid with behavioral disabilities such as insomnia and depression. Neonatal anoxia, a worldwide clinical problem in both neonatal and pediatric care, causes long-term deficits similar to those mentioned. The effect of neonatal anoxia on the maturation of nociceptive pathways has been sparsely explored. To address this question and to determine whether the effects differ depending on sex, a neonatal anoxia model was used in which Wistar rat pups approximately 30 h old and of both sexes were placed in a chamber with 100% nitrogen flow at 3.5 L/min for 25 min at 36 °C ± 1 °C. After recovery, the animals (n = 16 in each group (anoxia and control; males and females)) were returned to their mothers. The control animals were subjected to the same conditions, but no gas exchange was performed. At postnatal day (PND) 18 and PND43, the animals were subjected to pain testing by stimulation of the hind paws with von Frey monofilaments. The results revealed a significant reduction (approximately 50%) in the pain threshold in the animals exposed to anoxia in comparison with their respective controls. The pain threshold increased between PND18 and PND43. A sex-based difference was observed in the male control group at PND18. Histological analysis revealed decreased cell numbers in the ventral posterolateral thalamic nucleus (VPL), with sex differences. These results demonstrate the long-lasting negative impact of neonatal anoxia and indicate the relevance of performing suitable approaches taking in consideration the possible sex differences.

Palmitoylethanolamide prevents neuroinflammation, reduces astrogliosis and preserves recognition and spatial memory following induction of neonatal anoxia-ischemia.

RATIONAL: Neonatal anoxia-ischemia (AI) particularly affects the central nervous system. Despite the many treatments that have been tested, none of them has proven to be completely successful. Palmitoylethanolamide (PEA) and oleoylethanolamide (OEA) are acylethanolamides that do not bind to CB1 or CB2 receptors and thus they do not present cannabinoid activity. These molecules are agonist compounds of peroxisome proliferator-activator receptor alpha (PPARα), which modulates the expression of different genes that are related to glucose and lipid metabolism, inflammation, differentiation and proliferation. OBJECTIVE: In the present study, we analyzed the effects that the administration of PEA or OEA, after a neonatal AI event, has over different areas of the hippocampus. METHODS: To this end, 7-day-old rats were subjected to AI and then treated with vehicle, OEA (2 or 10 mg/kg) or PEA (2 or 10 mg/kg). At 30 days of age, animals were subjected to behavioral tests followed by immunohistochemical studies. RESULTS: Results showed that neonatal AI was associated with decreased locomotion, as well as recognition and spatial memory impairments. Furthermore, these deficits were accompanied with enhanced neuroinflammation and astrogliosis, as well as a decreased PPARα expression. PEA treatment was able to prevent neuroinflammation, reduce astrogliosis and preserve cognitive functions. CONCLUSIONS: These results indicate that the acylethanolamide PEA may play an important role in the mechanisms underlying neonatal AI, and it could be a good candidate for further studies regarding neonatal AI treatments.

Tempol (4 hydroxy-tempo) inhibits anoxia-induced progression of mitochondrial dysfunction and associated neurobehavioral impairment in neonatal rats.

BACKGROUND: Anoxia leads to a robust generation of reactive oxygen species/nitrogen species which can result in mitochondrial dysfunction and associated cell death in the cerebral cortex of neonates. AIM: The present study investigated the pharmacological role of tempol in the treatment of rat neonatal cortical mitochondrial dysfunction induced insult progression (day-1 to day-7) and associated neurobehavioral alterations post-anoxia. METHODS: Rat pups of 30h age or postnatal day 2 (PND2) were randomly divided into 5 groups (n=5 per group): (1) Control; (2) Anoxia; (3) Anoxia+Tempol 75mg/kg; (4) Anoxia+Tempol 150mg/kg; and (5) Anoxia+Tempol 300mg/kg, and subjected to two episode of anoxia (10min each) at 24h of time interval in an enclosed chamber supplied with 100% N2. RESULTS: Tempol significantly decreased nitric oxide (NO) formation and simultaneously improved superoxide dismutase (SOD) and catalase (CAT) activities. Further, we observed a significantly (P<0.05) improvement in mitochondrial respiration, complex enzyme activities, mitochondrial membrane potential (MMP) along with attenuation of transition pore opening (MPT) after treatment with tempol. Furthermore, tempol decreased expression of mitochondrial Bax, cytochrome-C, caspase-9 and caspase-3 while the increase in expression of cytoplasmic Bax, mitochondrial Bcl-2 on day-7 in cortical region indicating regulation of intrinsic pathway of apoptosis. Further, it improved anoxia-induced neurobehavioral outcome (hanging and reflex latencies). CONCLUSION: Biochemical, molecular and behavioral studies suggest the role of tempol in preserving mitochondrial function and associated neurobehavioral outcomes after neonatal anoxia.

Deferoxamine improves antioxidative protection in the brain of neonatal rats: The role of anoxia and body temperature.

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.

Impact of neonatal anoxia on adult rat hippocampal volume, neurogenesis and behavior.

Neonates that suffer oxygen deprivation during birth can have long lasting cognitive deficits, such as memory and learning impairments. Hippocampus, one of the main structures that participate in memory and learning processes, is a plastic and dynamic structure that conserves during life span the property of generating new cells which can become neurons, the so-called neurogenesis. The present study investigated whether a model of rat neonatal anoxia, that causes only respiratory distress, is able to alter the hippocampal volume, the neurogenesis rate and has functional implications in adult life. MRI analysis revealed significant hippocampal volume decrease in adult rats who had experienced neonatal anoxia compared to control animals for rostral, caudal and total hippocampus. In addition, these animals also had 55.7% decrease of double-labelled cells to BrdU and NeuN, reflecting a decrease in neurogenesis rate. Finally, behavioral analysis indicated that neonatal anoxia resulted in disruption of spatial working memory, similar to human condition, accompanied by an anxiogenic effect. The observed behavioral alterations caused by oxygen deprivation at birth might represent an outcome of the decreased hippocampal neurogenesis and volume, evidenced by immunohistochemistry and MRI analysis. Therefore, based on current findings we propose this model as suitable to explore new therapeutic approaches.