•Early environmental enrichment has affected developmental milestones.•Daily performance of reflexes was earlier improved in enriched rats.•Hypoxia-ischemia caused atrophy of striatum, corpus ...callosum and neocortex.•Early stimulation prevented the tissue damage on corpus callosum and neocortex.•Hypoxia-ischemia did not affect the sensorimotor development in neonate rats.
Our previous results demonstrated improved cognition in adolescent rats housed in environmental enrichment (EE) that underwent neonatal hypoxia-ischemia (HI). The aim of this study was to investigate the effects of early EE on neurobehavioral development and brain damage in rats submitted to neonatal HI. Wistar rats were submitted to the HI procedure on the 7th postnatal day (PND) and housed in an enriched environment (8th–20th PND). The maturation of physical characteristics and the neurological reflexes were evaluated and the volume of striatum, corpus callosum and neocortex was measured. Data analysis demonstrated a clear effect of EE on neurobehavioral development; also, daily performance was improved in enriched rats on righting, negative geotaxis and cliff aversion reflex. HI caused a transient motor deficit on gait latency. Brain atrophy was found in HI animals and this damage was partially prevented by the EE. In conclusion, early EE stimulated neurobehavioral development in neonate rats and also protects the neocortex and the corpus callosum from atrophy following HI. These findings reinforce the potential of EE as a strategy for rehabilitation following neonatal HI and provide scientific support to the use of this therapeutic strategy in the treatment of neonatal brain injuries in humans.
Background:
Methylphenidate (MPH) is a stimulant drug mainly prescribed to treat cognitive impairments in attention-deficit/hyperactivity disorder (ADHD). We demonstrated that neonatal ...hypoxia-ischemia (HI) induced attentional deficits in rats and MPH administration reversed these deficits. However, MPH effects on memory deficits after the HI procedure have not been evaluated yet.
Aims:
We aimed to analyze learning and memory performance of young hypoxic-ischemic rats after MPH administration and associate their performance with brain-derived neurotrophic factor (BDNF) levels in the prefrontal cortex and hippocampus.
Methods:
Male Wistar rats were divided into four groups (n=11–13/group): control saline (CTS), control MPH (CTMPH), HI saline (HIS) and HIMPH. The HI procedure was conducted at post-natal day (PND) 7 and memory tasks between PND 30 and 45. MPH administration (2.5 mg/kg, i.p.) occurred 30 min prior to each behavioral session and daily, for 15 days, for the BDNF assay (n=5–7/group).
Results:
As expected, hypoxic-ischemic animals demonstrated learning and memory deficits in the novel-object recognition (NOR) and Morris water maze (MWM) tasks. However, MPH treatment did not improve learning and memory deficits of these animals in the MWM—and even disrupted the animals’ performance in the NOR task. Increased BDNF levels were found in the hippocampus of HIMPH animals, which seem to have been insufficient to improve memory deficits observed in this group.
Conclusions:
The MPH treatment was not able to improve memory deficits resulting from the HI procedure considering a dose of 2.5 mg/kg. Further studies investigating different MPH doses would be necessary to determine a dose–response relationship in this model.
Hypoxia–ischemia (HI) is the main cause of mortality in the perinatal period and morbidity, in survivors, which is characterized by neurological disabilities. The immature brain is highly susceptible ...to hypoxic–ischemic insult and is responsive to environmental stimuli, such as environmental enrichment (EE). Previous results indicate that EE recovered memory deficits in adult rats without reversing hippocampal atrophy related to HI. The aim of this study was to investigate behavioral performance in the open field and rota-rod apparatuses, in object recognition and inhibitory avoidance tasks, as well as dendritic spine density in the hippocampus, in rats undergoing HI and exposed to EE. Seven-day old male rats were submitted to the HI procedure and divided into 4 groups: control maintained in standard environment (CTSE), controls submitted to EE (CTEE), HI in standard environment (HISE) and HI in EE (HIEE). Behavioral and morphological parameters were evaluated 9weeks after the environmental stimulation. Results indicate impairment in the object recognition task after HI that was recovered by enrichment; however the aversive memory impairment in the inhibitory avoidance task shown by hypoxic–ischemic rats was independent of the environment condition. Hypoxic–ischemic groups showed more crossing responses during the first minute in the open field, when compared to controls, but no differences were found between experimental groups in the rota-rod test. Dendritic spine density in the CA1 subfield of the right hippocampus (ipsilateral to the artery occlusion) was decreased after the HI insult, and increased in enriched controls; interestingly enriched HI rats did not differ from CTSE. In conclusion, EE was effective in recovering declarative memory impairment in object recognition and preserved hippocampal dendritic spine density loss after neonatal HI injury.
► Decreased spine density was identified in hippocampus of the hypoxic-ischemic rats. ► Environmental enrichment enhances dendritic spine density in hypoxic-ischemic animals. ► Enrichment did not recover aversive memory deficit after hypoxic-ischemic event. ► Object-recognition memory deficit was reversed by the enrichment. ► Control and hypoxic-ischemic groups showed no motor deficits in the rota-rod test.
Recent findings have demonstrated a dual effect of the folic acid (FA) supplementation on the nervous system of rats. We found that FA treatment prevented memory impairment and Na(+), K(+)- ATPase ...inhibition in the striatum and cortex in adult rats that suffered neonatal hypoxia-ischemia (HI). However, spatial memory deficit has been associated with FA supplementation. In the present study we investigated the role of FA supplementation on spatial memory and Na(+), K(+)-ATPase activity in the hippocampus, as well as on morphologic alterations in adolescent rats submitted to neonatal HI. Wistar rats of both sexes at postnatal day (PND) 7 were submitted to Levine-Rice HI procedure. Intraperitoneal doses of FA were administered immediately before HI and repeated daily until the maximum PND 40. Hippocampal volume and striatum area were estimated and Na(+), K(+)-ATPase activity in the hippocampus was measured at PND 31. Also, the performance of the animals in the water maze was assessed and Na(+), K(+)-ATPase activity measured again at PND 52. Interestingly, HI and FA resulted in spatial memory deficits in the Morris water maze and the Na(+), K(+)-ATPase activity was impaired at PND 31 in HI rats which received FA. Additionally, Na(+), K(+)-ATPase activity in adulthood showed a decrease after HI and a recovery in supplemented animals. Hippocampal and striatal atrophy were partially reversed by FA. To conclude, the present results support the hypothesis that FA supplementation during development contributes to memory deficits caused by HI and Na(+), K(+)-ATPase failure in adolescent rats, although, in adulthood, FA has been effective in reversing enzymatic activity in the hippocampus.
Impulsivity, as observed in patients diagnosed with Attention-deficit/hyperactivity disorder (ADHD), can induce dysregulated behaviors such as binge eating and drug addiction. We previously ...demonstrated that neonatal hypoxia-ischemia (HI) resulted in ADHD-like behaviors in rats and that methylphenidate (MPH) administration (the first therapeutic option for ADHD) reversed these deficits. Here, we aimed at investigating addictive-like behaviors, such as the reward-based feeding behavior (using the BioDAQ monitor) and ethanol consumption (using the IA2BC procedure) in adult animals subjected to neonatal HI and treated with or without MPH. Male Wistar rats were divided into four groups (n = 10–12/group): control saline (CTS), CTMPH, HI saline (HIS) and HIMPH. The HI procedure was conducted at postnatal day (PND) 7 and behavioral analyses between PND 60–90, in which MPH (2.5 mg/kg, i.p.) was administered 30 min prior to each behavioral evaluation (6 sessions in BioDAQ and 12 sessions in the IA2BC protocol). HI animals had a dysregulated feeding intake shortly after eating a small piece of the palatable diet, and MPH reversed this dysregulated pattern. However, when the palatable diet was freely available, MPH stimulated a higher intake of this diet in the first exposure day, and this effect was potentialized in HIMPH rats. Increased ethanol intake was observed in HI rats, and MPH administration alleviated this behavior; contrarily, MPH treatment in control rats induced an increase in ethanol consumption. The present findings give additional support to the relationship between neonatal HI and ADHD but the differential response to MPH in control or HI animals highlights the importance of avoiding indiscriminate use of MPH by healthy individuals.
•Neonatal hypoxia-ischemia (HI) induced ADHD-related outcomes in rats.•Methylphenidate (MPH) reversed or reduced addictive-like behaviors in HI rats.•MPH altered the sensitivity to reward in both HI and control (CT) groups.•MPH showed differential effects concerning ethanol consumption in CT or HI rats.
Folic acid (FA) supplementation (400 μg/day) has been recommended during pregnancy to prevent neural tube defects. However, in some countries, flours are required to be fortified with FA, possibly ...increasing the levels of this vitamin in pregnant women. Our previous studies have evidenced a dual effect of the FA treatment in a rat model of neonatal hypoxia-ischemia (HI). Aiming to better correlate with humans, this paper evaluated the effects of two different levels of FA supplementation during pregnancy on memory parameters and neuronal survival and plasticity in the hippocampus of rats submitted to the neonatal HI. During pregnancy, female Wistar rats received one of these diets: standard (SD), supplemented with 2 mg/kg of FA or with 20 mg/kg of FA. At the 7th PND, rats suffered the HI procedure. At the 60th PND rats were evaluated in the open field, Morris water maze, novel-object recognition and inhibitory avoidance tasks. Furthermore, neuronal density, synaptophysin densitometry and BDNF concentration were assessed in the hippocampus. Both doses of FA prevented the HI-induced memory impairments. The supplementation reversed the BDNF late increase in the hippocampus of the HI rats, but did not inhibit the neuronal death. In conclusion, FA supplementation during pregnancy prevented memory deficits and BDNF imbalance after neonatal HI. These findings are particularly relevant because neuroprotection was achieved even in the high level of FA supplementation during pregnancy, indicating that this intervention would be considered secure for the offspring development.
•Exercise was able to reverse the hyperactivity after the neonatal hypoxia-ischemia.•The acrobatic training decreased brain atrophy caused by neonatal hypoxia-ischemia.•The acrobatic exercise caused ...locomotion improvement after the hypoxia-ischemia.•Neonatal hypoxia-ischemia did not impact on morphology in motor control structures.
The aim of this study was to evaluated motor function and morphological aspects of the components involved in motor control (sensorimotor cortex, spinal cord, sciatic nerve, neuromuscular junctions and skeletal muscle) in male Wistar rats exposed to a model of neonatal hypoxic-ischemic encephalopathy (HIE) and the possible influence of different physical exercise protocols – treadmill and acrobatic. Male Wistar rats at the 7th post-natal day (PND) were submitted to the HIE model and from the 22nd until 60th PND the exercise protocols (treadmill or acrobatic training) were running. After the training, the animals were evaluated in Open Field, Ladder Rung Walking and Rotarod tasks and after samples of the motor control components were collected. Our results evidenced that the acrobatic training reversed the hyperactivity and anxiety, caused locomotion improvement and decreased brain atrophy in HIE animals. We did not find morphological differences on sensorimotor cortex, spinal cord, sciatic nerve, neuromuscular junctions and skeletal muscle in the animals submitted to HIE model. These intriguing data support the statement of the Rice-Vannucci model does not seem to reproduce, in structures involved in control function, the damage found in humans that suffer HIE. Regarding the protocols of exercise, we proposed that the acrobatic exercise could be a good therapeutic option especially in children affected by neonatal HIE and can be responsible for good results in cognitive and motor aspects.
•Congenital Zika virus infection caused offspring’s neurobehavioral development delay.•Gestational Zika virus damaged the offspring’s blood–brain barrier.•Gestational Zika virus infection causes ...progeny’s oxidative stress imbalance.
Zika virus (ZIKV) is a mosquito-borne flavivirus associated with several neurodevelopmental outcomes after in utero infection. Here, we studied a congenital ZIKV infection model with immunocompetent Wistar rats, able to predict disabilities and that could pave the way for proposing new effective therapies. We identified neurodevelopmental milestones disabilities in congenital ZIKV animals. Also, on 22nd postnatal day (PND), blood–brain barrier (BBB) proteins disturbances were detected in the hippocampus with immunocontent reduction of β_Catenin, Occludin and Conexin-43. Besides, oxidative stress imbalance on hippocampus and cortex were identified, without neuronal reduction in these structures. In conclusion, even without pups’ microcephaly-like phenotype, congenital ZIKV infection resulted in neurobehavioral dysfunction associated with BBB and oxidative stress disturbances in young rats. Therefore, our findings highlighted the multiple impact of the congenital ZIKV infection on the neurodevelopment, which reinforces the continuity of studies to understand the spectrum of this impairment and to provide support to future treatment development for patients affected by congenital ZIKV.
Perinatal complications such as birth asphyxia were associated with a higher risk for Attention-Deficit/Hyperactivity Disorder (ADHD) in humans. Data from a rat model of neonatal hypoxia-ischemia ...(HI) have revealed inattention, impulsive behavior and dopamine (DA) disturbances in the prefrontal cortex (PFC), confirming the face validity and construct validity for ADHD study. However, the predictive validity (similar therapeutic efficacy of the pharmacological treatment available in the clinic) should be considered. Therefore, we aimed to investigate the effects of methylphenidate (MPH) - the treatment of choice for ADHD - on exploratory and attentional flexibility behaviors and DA-related proteins in the PFC of animals submitted to neonatal HI. Male Wistar rats were divided into four groups: control saline (CTS, n = 12), control MPH (CTMPH, n = 12), HI saline (HIS, n = 13) and HIMPH (n = 12). The HI procedure was conducted at postnatal day (PND) 7 and behavioral measures between PND 30–40, followed by protein analysis in the PFC. The MPH administration (2.5 mg/kg, i.p.) occurred 30 min prior each behavioral session and euthanasia for western blot analysis. We observed that the MPH increased the locomotor activity in the open field especially in HI rats. In the attentional-set shifting task, the MPH reversed the HI- induced attentional inflexibility, but impaired the task acquisition in control rats. Neonatal HI resulted in lower DA D2 receptors expression but also decreased DA transporter (responsible for DA reuptake) and increased pTH (phosphorylated-tyrosine hydroxylase) levels in the PFC, probably to compensate the dysfunctional DA transmission. This compensation was higher in the HIMPH group and it could explain the improvement in the attentional flexibility as well as the increased locomotor activity in this group. Taken this data together, we can assume the predictive validity of the HI model for the ADHD study concerning the impact of MPH treatment on attentional parameters.
•Methylphenidate increased locomotor activity especially in hypoxic-ischemic rats.•Neonatal hypoxia-ischemia impaired attentional flexibility in adolescent rats.•Methylphenidate reversed attentional inflexibility resulting from hypoxia-ischemia.•Task acquisition learning was impaired by the methylphenidate in control rats.•Hypoxia-ischemia disrupted the dopaminergic system in the prefrontal cortex.
Perinatal asphyxia is a peripartum event that can cause permanent sequelae to the newborns, affecting the brain development. Recently, it has been demonstrated that epigenetics mechanisms play an ...important role in this injury and that folic acid (FA) supplementation during pregnancy can affect these epigenetics modifications as well as gene expression. We have identified both positive and negative effects of FA treatment in rats submitted to a model of neonatal hypoxia‐ischemia (HI). Considering that FA supplementation is already used in pregnant women and that HI occurs in the peripartum period, this study was designated to evaluate how gestational FA supplementation and neonatal HI affect: apoptosis (caspase‐3) and expression of synaptic proteins (synapsin and PSD‐95) and the methylation of histone H3 lysine (K) 4 and 27 in the rat hippocampus. Pregnant Wistar rats were divided according to the diets: standard (SD), supplemented with 2 mg/kg of FA or with 20 mg/kg of FA. HI procedure was performed at the 7th PND. Protein expression and H3 methylation were evaluated at the 60th PND in the rats’ hippocampus. Neonatal HI increased caspase‐3 expression decreased synapsin expression and reduced H3K4me2, ‐me3 and H3K27me2, ‐me3 in the ipsilateral hippocampus. FA only prevented the augment in caspase‐3 expression. In conclusion, neonatal HI caused lasting effects on caspase‐3‐mediated cell death (prevented by the FA) and synaptic proteins in the rats’ hippocampus. This is the first study to show that histone modifications may contribute to these pathological findings in the hippocampus of HI animals.
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