Tissue Injury and Astrocytic Reaction, But Not Cognitive Deficits, Are Dependent on Hypoxia Duration in Very Immature Rats Undergoing Neonatal Hypoxia-Ischemia.

Preterm birth and hypoxia-ischemia (HI) are major causes of neonatal death and neurological disabilities in newborns. The widely used preclinical HI model combines carotid occlusion with hypoxia exposure; however, the relationship between different hypoxia exposure periods with brain tissue loss, astrocyte reactivity and behavioral impairments following HI is lacking. Present study evaluated HI-induced behavioral and morphological consequences in rats exposed to different periods of hypoxia at postnatal day 3. Wistar rats of both sexes were assigned into four groups: control group, HI-120 min, HI-180 min and HI-210 min. Neurodevelopmental reflexes, exploratory abilities and cognitive function were assessed. At adulthood, tissue damage and reactive astrogliosis were measured. Animals exposed to HI-180 and HI-210 min had delayed neurodevelopmental reflexes compared to control group. Histological assessment showed tissue loss that was restricted to the ipsilateral hemisphere in lower periods of hypoxia exposure (120 and 180 min) but affected both hemispheres when 210 min was used. Reactive astrogliosis was increased only after 210 min of hypoxia. Interestingly, cognitive deficits were induced regardless the duration of hypoxia and there were correlations between behavioral parameters and cortex, hippocampus and corpus callosum volumes. These results show the duration of hypoxia has a close relationship with astrocytic response and tissue damage progression. Furthermore, the long-lasting cognitive memory deficit and its association with brain structures beyond the hippocampus suggests that complex anatomical changes should be involved in functional alterations taking place as hypoxia duration is increased, even when the cognitive impairment limit is achieved.

Dual influences of early life stress induced by limited bedding on walking adaptability and Bdnf/TrkB and Drd1/Drd2 gene expression in different mouse brain regions.

Introduction Evidence suggests early life stress impairs development, quality of life and increases vulnerability to disease. One important aspect of the stress experience is its impact on cognitive-motor performance, which includes the ability to adapt walking according to the environmental conditions. This study aimed to investigate how early-life stress affects walking adaptability of mice, while investigating BDNF/TrkB and Drd1/Drd2 expression in different brain regions. Methods Briefly, we exposed male C56BL/6 to the limited bedding protocol (LB) from post-natal day (PND) 2 to PND9 and then tested animals in the ladder walking task at PND60. RT-qPCR was used to investigate gene expression in the mPFC, hippocampus, motor cortex and cerebellum 2 h after the task Results LB induced a wide range of variability and therefore two distinct subgroups of animals within the LB group were established: a) superior performance (LB-SP); and b) inferior performance (LB-IP), compared to controls. Additionally, Drd1 gene expression was increased in the mPFC of LB-IP animals and in the cerebellum of LB-SP animals, while Drd2 expression was reduced in the hippocampus of the LB-IP group. BDNF exon IV gene expression in the mPFC and motor cortex was increased in both the LB-IP and LB-SP subgroups. TrkB gene expression in the hippocampus was reduced in the LB-IP group. A strong negative correlation was found between walking adaptability performance and BDNF exon IV gene expression in the motor cortex. Conversely, a positive correlation was found between walking adaptability performance and TrkB expression in the mPFC and a negative correlation in the hippocampus. Both Drd1 and Drd2 gene expression were negatively correlated with the ability to adapt walking. Conclusions Overall, our findings suggest exposure to early life stress leads to distinct walking adaptability phenotypes, which may be related to Drd1, Drd2, Bdnf exon IV and TrkB gene expression in brain regions that influence walking adaptability.

Glial glutamate transporters expression, glutamate uptake, and oxidative stress in an experimental rat model of intracerebral hemorrhage.

Glial glutamate transporters (EAAT1 and EAAT2), glutamate uptake, and oxidative stress are important players in the pathogenesis of ischemic brain injury. However, the changes in EAAT1 and EAAT2 expression, glutamate uptake and the oxidative profile during intracerebral hemorrhage (ICH) development have not been described. The present study sought to investigate the changes of the above-mentioned variables, as well as the Na+/K+-ATPase and glutamine synthetase activities (as important contributors of glutamate homeostasis) and the percentage of neuronal cells after 6 h, 24 h, 72 h and 7 days of ICH. An injection of 0.2U of bacterial collagenase in the ipsilateral striatum was used to induce ICH in male Wistar rats; naïve animals were used as controls. EAAT1 and EAAT2 expression and glutamate uptake in the ipsilateral striatum were assessed. Additionally, the percentage of MAP2+ cells, Na+/K+-ATPase and GS activities, as well as the oxidative profile were analyzed. It is shown a decrease of EAAT1 expression and glutamate uptake 6 h post-ICH, whereas EAAT2 decreased 72 h after the event; conversely EAAT2 and glutamate uptake were increased after 7 days. The oxidative stress and endogenous defense system exhibited a remarkable response at 72 h of injury. ICH also increased Na+/K+-ATPase activity and selectively decreased GS activity, variables known to be important contributors of glial glutamate transporters activities. Altogether, present findings indicate that ICH induces different temporal EAAT1 and EAAT2 responses, culminating with an imbalance of glutamate uptake capacity, increased oxidative stress and sustained neuronal loss.

Glial-associated changes in the cerebral cortex after collagenase-induced intracerebral hemorrhage in the rat striatum.

Striatum and the cerebral cortex are regions susceptible to secondary injury after intracerebral hemorrhage (ICH) and glial cells in tissue adjacent to the hematoma may modulate cellular vulnerability after brain damage. Nonetheless, while the glial- associated changes occurring in the cerebral cortex after ICH may be important in maximizing brain recovery, they are not fully understood. The aim of this study was to evaluate the temporal profile of glial-associated changes in the cerebral cortex after ICH. First, the motor consequences of ICH and its relation to the lesion volume were analyzed. Secondly, glial cell proportion (GFAP+ and S100B+ astrocytes, CD11+ microglia) in the ipsilesional sensorimotor cortex and striatum, using flow cytometry were evaluated. ELISA was used to measure GFAP and S100B content in these structures as well as S100B levels in serum and cerebral spinal fluid. Main results revealed that ICH induced a delayed increase in GFAP+ cells in the sensorimotor cortex, as compared to the striatum, although the pattern of GFAP expression was similar in both structures. Interestingly, the time-curve patterns of both S100B and CD11+ microglial cells differed between the cortex and striatum. Altogether, these results suggest a different dynamics of glial-associated changes in the cerebral cortex, suggesting it is a vulnerable structure and undergoes an independent secondary process of reactive glial plasticity following intracerebral hemorrhage.

Motor Skill Training Promotes Sensorimotor Recovery and Increases Microtubule-Associated Protein-2 (MAP-2) Immunoreactivity in the Motor Cortex after Intracerebral Hemorrhage in the Rat.

Motor skill learning may induce behavioral and neurophysiological adaptations after intracerebral hemorrhage (ICH). Learning a new motor skill is associated with dendritic reorganization and requires protein synthesis and expression of MAP-2. The purpose of this study was to evaluate motor performance and expression of MAP-2 in the motor cortex of rats submitted to intracerebral hemorrhage model (ICH) and skill task training (SK) or unskilled training (US) during 4 weeks. The Staircase test was used for behavioral evaluation, and relative optical densities and morphometrical analysis were used to estimate MAP-2 immunoreactivity and parameters of brain tissue in both motor cortices. Results show that skill task training performed with the impaired forelimb was able to increase MAP-2 immunoreactivity in the motor cortex either in sham or in ICH groups in both cortices: ipsilesional [F (5,35) = 14.25 (P < 0.01)] and contralesional hemispheres [F (5,35) = 9.70 (P < 0.01)]. ICH alone also increased MAP-2 immunoreactivity despite the absence of functional gains. Behavioral evaluation revealed that ICH-SK group performed better than ICH and ICH-US animals in the Staircase test. Data suggest that motor skill training induces plastic modifications in both motor cortices, either in physiological or pathological conditions and that skill motor training produces higher brain plasticity and positive functional outcomes than unskilled training after experimental intracerebral hemorrhage.

Effects of skilled and unskilled training on functional recovery and brain plasticity after focal ischemia in adult rats.

Stroke is a leading cause of morbidity and mortality worldwide. Recovery of motor function after stroke can be modified by post-injury experience, but most of surviving patients exhibit persistence of the motor dysfunctions even after rehabilitative therapy. In this study we investigated if skilled and unskilled training induce different motor recovery and brain plasticity after experimental focal ischemia. We tested this hypothesis by evaluating the motor skill relearning and the immunocontent of Synapsin-I, PSD-95 and GFAP (pre and post-synaptic elements, as well as surrounding astroglia) in sensorimotor cortex of both hemispheres 6 weeks after endothelin-1-induced focal brain ischemia in rats. Synapsin-I and PSD-95 levels were increased by skilled training in ischemic sensorimotor cortex. The content of GFAP was augmented as a result of focal brain ischemia in ischemic sensorimotor cortex and that was not modified by rehabilitation training. Unexpectedly, animals remained permanently impaired at the end of motor/functional evaluations. Significant modifications in protein expression were not observed in undamaged sensorimotor cortex. We conclude that skilled motor activity can positively affect brain plasticity after focal ischemia despite of no functional improvement in conditions here tested.

Skilled reaching training promotes astroglial changes and facilitated sensorimotor recovery after collagenase-induced intracerebral hemorrhage.

Spontaneous intracerebral hemorrhage (ICH) is the most devastating type of stroke and a leading cause of disability and mortality worldwide. Although rehabilitation improves recovery after ICH the cellular mechanisms involved are poorly understood. We decided to examine if skilled (SK) and unskilled (US) training after sham or intracerebral hemorrhage (ICH) surgeries would induce GFAP+ astrocytic changes and whether these modifications can be associated with functional improvement. A 4-week course of motor training, involving either skilled and unskilled training began seven days after surgery; sensorimotor recovery was evaluated using Staircase, ladder walk and cylinder tests. Histological and morphometric analyses were used to assess GFAP+ cell bilaterally in forelimb sensorimotor cortex and dorsolateral striatum. All behavioral tests showed that ICH-SK rats experienced a greater degree of recovery when compared to ICH no task or ICH-US groups; no behavioral differences were found among all sham groups. Astrocytic density was increased in all analyzed structures for ICH no task, ICH-SK and ICH-US rats. Morphological analysis revealed an increased number of primary processes in ipsilateral (to lesion) sensorimotor cortex for all ICH groups. Present results also revealed that both ICH and SK induced an increased length of GFAP+ primary process; there was a further increase in length processes for ICH-SK group in sensorimotor cortex and ipsilateral striatum. We suggest that skilled reaching is an effective intervention to promote astrocytic plasticity and recovery after ICH.