Maternal environmental enrichment protects neonatal brains from hypoxic-ischemic challenge by mitigating brain energetic dysfunction and modulating glial cell responses.

There is evidence that maternal milieu and changes in environmental factors during the prenatal period may exert a lasting impact on the brain health of the newborn, even in case of neonatal brain hypoxia-ischemia (HI). The present study aimed to investigate the effects of maternal environmental enrichment (EE) on HI-induced energetic and metabolic failure, along with subsequent neural cell responses in the early postnatal period. Male Wistar pups born to dams exposed to maternal EE or standard conditions (SC) were randomly divided into Sham-SC, HI-SC, Sham-EE, and HI-EE groups. Neonatal HI was induced on postnatal day (PND) 3. The Na+,K+-ATPase activity, mitochondrial function and neuroinflammatory related-proteins were assessed at 24 h and 48 h after HI. MicroPET-FDG scans were used to measure glucose uptake at three time points: 24 h post-HI, PND18, and PND24. Moreover, neuronal preservation and glial cell responses were evaluated at PND18. After HI, animals exposed to maternal EE showed an increase in Na+,K+-ATPase activity, preservation of mitochondrial potential/mass ratio, and a reduction in mitochondrial swelling. Glucose uptake was preserved in HI-EE animals from PND18 onwards. Maternal EE attenuated HI-induced cell degeneration, white matter injury, and reduced astrocyte immunofluorescence. Moreover, the HI-EE group exhibited elevated levels of IL-10 and a reduction in Iba-1 positive cells. Data suggested that the regulation of AKT/ERK1/2 signaling pathways could be involved in the effects of maternal EE. This study evidenced that antenatal environmental stimuli could promote bioenergetic and neural resilience in the offspring against early HI damage, supporting the translational value of pregnancy-focused environmental treatments.

Protective effect of sex steroid hormones on morphological and cellular outcomes after neonatal hypoxia-ischemia: A meta-analysis of preclinical studies.

Sex steroid hormones play an important role in fetal development, brain functioning and neuronal protection. Growing evidence highlights the positive effects of these hormones against brain damage induced by neonatal hypoxia-ischemia (HI). This systematic review with meta-analysis aims to verify the efficacy of sex steroid hormones in preventing HI-induced brain damage in rodent models. The protocol was registered at PROSPERO and a total of 22 articles were included. Moderate to large effects were observed in HI animals treated with sex steroid hormones in reducing cerebral infarction size and cell death, increasing neuronal survival, and mitigating neuroinflammatory responses and astrocyte reactivity. A small effect was evidenced for cognitive function, but no significant effect for motor function; moreover, a high degree of heterogeneity was observed. In summary, data suggest that sex steroid hormones, such as progesterone and 17ß estradiol, improve morphological and cellular outcomes following neonatal HI. Further research is paramount to examine neurological function during HI recovery and standardization of methodological aspects is imperative to reduce the risk of spurious findings.

Arundic Acid (ONO-2506) Attenuates Neuroinflammation and Prevents Motor Impairment in Rats with Intracerebral Hemorrhage.

Intracerebral hemorrhage (ICH) is a severe stroke subtype caused by the rupture of blood vessels within the brain. Increased levels of S100B protein may contribute to neuroinflammation after ICH through activation of astrocytes and resident microglia, with the consequent production of proinflammatory cytokines and reactive oxygen species (ROS). Inhibition of astrocytic synthesis of S100B by arundic acid (AA) has shown beneficial effects in experimental central nervous system disorders. In present study, we administered AA in a collagenase-induced ICH rodent model in order to evaluate its effects on neurological deficits, S100B levels, astrocytic activation, inflammatory, and oxidative parameters. Rats underwent stereotactic surgery for injection of collagenase in the left striatum and AA (2 µg/µl; weight × 0.005) or vehicle in the left lateral ventricle. Neurological deficits were evaluated by the Ladder rung walking and Grip strength tests. Striatal S100B, astrogliosis, and microglial activation were assessed by immunofluorescence analysis. Striatal levels of interleukin 1ß (IL-1ß) and tumor necrosis factor α (TNF-α) were measured by ELISA, and the ROS production was analyzed by dichlorofluorescein (DCF) oxidation. AA treatment prevented motor dysfunction, reduced S100B levels, astrogliosis, and microglial activation in the damaged striatum, thus decreasing the release of proinflammatory cytokines IL-1ß and TNF-α, as well as ROS production. Taken together, present results suggest that AA could be a pharmacological tool to prevent the harmful effects of increased S100B, attenuating neuroinflammation and secondary brain damage after ICH.

Chronic mild hyperhomocysteinemia induces anxiety-like symptoms, aversive memory deficits and hippocampus atrophy in adult rats: New insights into physiopathological mechanisms.

In the last decade, increased homocysteine levels have been implicated as a risk factor for neurodegenerative and psychiatric disorders. We have developed an experimental model of chronic mild hyperhomocysteinemia (HHcy) in order to observe metabolic impairments in the brain of adult rodents. Besides its known effects on brain metabolism, the present study sought to investigate whether chronic mild HHcy could induce learning/memory impairments associated with biochemical and histological damage to the hippocampus. Adult male Wistar rats received daily subcutaneous injections of homocysteine (0.03 µmol/g of body weight) twice a day, from the 30th to the 60th day of life or saline solution (Controls). After injections, anxiety-like and memory tests were performed. Following behavioral analyses, brains were sliced and hippocampal volumes assessed and homogenized for redox state assessment, antioxidant activity, mitochondrial functioning (chain respiratory enzymes and ATP levels) and DNA damage analyses. Behavioral analyses showed that chronic mild HHcy may induce anxiety-like behavior and impair long-term aversive memory (24 h) that was evaluated by inhibitory avoidance task. Mild HHcy decreased locomotor and/or exploratory activities in elevated plus maze test and caused hippocampal atrophy. Decrease in cytochrome c oxidase, DNA damage and redox state changes were also observed in hippocampus of adult rats subjected to mild HHcy. Our findings show that chronic mild HHcy alters biochemical and histological parameters in the hippocampus, leading to behavioral impairments. These findings might be considered in future studies aiming to search for alternative strategies for treating the behavioral impairments in patients with mild elevations in homocysteine levels.

Prenatal and Early Postnatal Environmental Enrichment Reduce Acute Cell Death and Prevent Neurodevelopment and Memory Impairments in Rats Submitted to Neonatal Hypoxia Ischemia.

Environmental enrichment (EE) is an experimental strategy to attenuate the negative effects of different neurological conditions including neonatal hypoxia ischemia encephalopathy (HIE). The aim of the present study was to investigate the influence of prenatal and early postnatal EE in animals submitted to neonatal HIE model at postnatal day (PND) 3. Wistar rats were housed in EE or standard conditions (SC) during pregnancy and lactation periods. Pups of both sexes were assigned to one of four experimental groups, considering the early environmental conditions and the injury: SC-Sham, SC-HIE, EE-sham, and EE-HIE. The offspring were euthanized at two different time points: 48 h after HIE for biochemical analyses or at PND 67 for histological analyses. Behavioral tests were performed at PND 7, 14, 21, and 60. Offspring from EE mothers had better performance in neurodevelopmental and spatial memory tests when compared to the SC groups. HIE animals showed a reduction of IGF-1 and VEGF in the parietal cortex, but no differences in BDNF and TrkB levels were found. EE-HIE animals showed reduction in cell death, lower astrocyte reactivity, and an increase in AKTp levels in the hippocampus and parietal cortex. In addition, the EE was also able to prevent the hippocampus tissue loss. Altogether, present findings point to the protective potential of the prenatal and early postnatal EE in attenuating molecular and histological damage, as well as the neurodevelopmental impairments and the cognitive deficit, caused by HIE insult at PND 3.

Human dental pulp stem cells transplantation combined with treadmill training in rats after traumatic spinal cord injury.

Spinal cord injury (SCI) is a disabling condition resulting in deficits of sensory and motor functions, and has no effective treatment. Considering that protocols with stem cell transplantation and treadmill training have shown promising results, the present study evaluated the effectiveness of stem cells from human exfoliated deciduous teeth (SHEDs) transplantation combined with treadmill training in rats with experimental spinal cord injury. Fifty-four Wistar rats were spinalized using NYU impactor. The rats were randomly distributed into 5 groups: Sham (laminectomy with no SCI, n=10); SCI (laminectomy followed by SCI, n=12); SHEDs (SCI treated with SHEDs, n=11); TT (SCI treated with treadmill training, n=11); SHEDs+TT (SCI treated with SHEDs and treadmill training; n=10). Treatment with SHEDs alone or in combination with treadmill training promoted functional recovery, reaching scores of 15 and 14, respectively, in the BBB scale, being different from the SCI group, which reached 11. SHEDs treatment was able to reduce the cystic cavity area and glial scar, increase neurofilament. Treadmill training alone had no functional effectiveness or tissue effects. In a second experiment, the SHEDs transplantation reduced the TNF-α levels in the cord tissue measured 6 h after the injury. Contrary to our hypothesis, treadmill training either alone or in combination, caused no functional improvement. However, SHEDs showed to be neuroprotective, by the reduction of TNF-α levels, the cystic cavity and the glial scar associated with the improvement of motor function after SCI. These results provide evidence that grafted SHEDs might be an effective therapy to spinal cord lesions, with possible anti-inflammatory action.

Human dental pulp stem cells transplantation combined with treadmill training in rats after traumatic spinal cord injury

Spinal cord injury (SCI) is a disabling condition resulting in deficits of sensory and motor functions, and has no effective treatment. Considering that protocols with stem cell transplantation and treadmill training have shown promising results, the present study evaluated the effectiveness of stem cells from human exfoliated deciduous teeth (SHEDs) transplantation combined with treadmill training in rats with experimental spinal cord injury. Fifty-four Wistar rats were spinalized using NYU impactor. The rats were randomly distributed into 5 groups: Sham (laminectomy with no SCI, n=10); SCI (laminectomy followed by SCI, n=12); SHEDs (SCI treated with SHEDs, n=11); TT (SCI treated with treadmill training, n=11); SHEDs+TT (SCI treated with SHEDs and treadmill training; n=10). Treatment with SHEDs alone or in combination with treadmill training promoted functional recovery, reaching scores of 15 and 14, respectively, in the BBB scale, being different from the SCI group, which reached 11. SHEDs treatment was able to reduce the cystic cavity area and glial scar, increase neurofilament. Treadmill training alone had no functional effectiveness or tissue effects. In a second experiment, the SHEDs transplantation reduced the TNF-α levels in the cord tissue measured 6 h after the injury. Contrary to our hypothesis, treadmill training either alone or in combination, caused no functional improvement. However, SHEDs showed to be neuroprotective, by the reduction of TNF-α levels, the cystic cavity and the glial scar associated with the improvement of motor function after SCI. These results provide evidence that grafted SHEDs might be an effective therapy to spinal cord lesions, with possible anti-inflammatory action.

Environmental stimulation improves performance in the ox-maze task and recovers Na+,K+-ATPase activity in the hippocampus of hypoxic-ischemic rats.

In animal models, environmental enrichment (EE) has been found to be an efficient treatment for alleviating the consequences of neonatal hypoxia-ischemia (HI). However the potential for this therapeutic strategy and the mechanisms involved are not yet clear. The aim of present study is to investigate behavioral performance in the ox-maze test and Na+,K+-ATPase, catalase (CAT) and glutathione peroxidase (GPx) activities in the hippocampus of rats that suffered neonatal HI and were stimulated in an enriched environment. Seven-day-old rats were submitted to the HI procedure and divided into four groups: control maintained in standard environment (CTSE), control submitted to EE (CTEE), HI in standard environment (HISE) and HI in EE (HIEE). Animals were stimulated with EE for 9 weeks (1 h/day for 6 days/week) and then behavioral and biochemical parameters were evaluated. Present results indicate learning and memory in the ox-maze task were impaired in HI rats and this effect was recovered after EE. Hypoxic-ischemic event did not alter the Na+,K+-ATPase activity in the right hippocampus (ipsilateral to arterial occlusion). However, on the contralateral hemisphere, HI caused a decrease in this enzyme activity that was recovered by EE. The activities of GPx and CAT were not changed by HI in any group evaluated. In conclusion, EE was effective in recovering learning and memory impairment in the ox-maze task and Na+,K+-ATPase activity in the hippocampus caused by HI. The present data provide further support for the therapeutic potential of environmental stimulation after neonatal HI in rats.

Are the consequences of neonatal hypoxia-ischemia dependent on animals' sex and brain lateralization?

Hypoxia-ischemia on 3-day-old rats (HIP3) allows the investigation of HI damage in the immature brain. HIP3 is characterized for neurological disabilities caused by white matter injury. This study investigates the relationship between animals' sex and injured hemisphere on HIP3 consequences. Male and female Wistar rats had their right or left common carotid artery occluded under halotane anesthesia and exposed to 8% O2 for 1.5 h. Control rats received sham surgery and exposure to 1.5 h of room air in isolation of their mothers. Sex and injured hemisphere influence in Na+/K+ -ATPase activity 24h after lesion: females and the right brain hemispheres showed decreased enzymatic activity after HIP3. Cognitive impairment was observed in step-down inhibitory avoidance, in which females HIP3 left injured were the most damaged. Histological analysis showed a trend to white matter damage in females left injured without hemispherical nor hippocampal volume decrease in HIP3 rats at postnatal day 21. However, at PND90, hemisphere and sex effects were noted in hemispherical volume and myelination: left brain hemisphere and the females evidenced higher histological damage. Our results points to an increased resistance of male rats and right brain hemisphere to support the impairment caused in Na+/K+ -ATPase activity early after HIP3, and evidencing more discrete behavioral impairments and histological damage at adulthood. Present data adds new evidence of distinct effects of brain lateralization and sex vulnerability on biochemical, behavioral and histological parameters after hypoxia-ischemia.

Early hypoxia-ischemia causes hemisphere and sex-dependent cognitive impairment and histological damage.

Neonatal cerebral hypoxia-ischemia (HI) is an important cause of neurological disorders. In the preterm children, HI causes preferentially white matter damage and late cognitive impairments. Rodent HI performed at postnatal day 3 (HIP3) provides valuable information on the brain response to injury in immature animals as related to sensory, motor and cognitive impairments observed in humans born prematurely. The present study aimed to observe the effects of brain lateralization and sexual dimorphism following HIP3 on behavior and histological damage assessed in adulthood. Male and female Wistar rats had their right or left common carotid artery occluded and exposed to 8% oxygen for 1.5h; control rats received sham surgery and exposure to 1.5h of room air in isolation of their dams. Sensory and cognitive parameters were assessed by the use of elevated plus maze, cylinder test and Morris water maze. After behavioral testing, hemisphere and hippocampus volumes were used to define brain damage extension; white matter damage was estimated through corpus callosum area ratio. No motor impairments were shown in HIP3 rats and anxiety-related changes were observed only in right injured animals. Females having left occlusion were more vulnerable to HIP3 injury since they presented spatial memory impairment and greater histological damage. These results show the modulation exerted by sex and brain lateralization following early HI at postnatal day 3.

Effect of skilled and unskilled training on nerve regeneration and functional recovery

The most disabling aspect of human peripheral nerve injuries, the majority of which affect the upper limbs, is the loss of skilled hand movements. Activity-induced morphological and electrophysiological remodeling of the neuromuscular junction has been shown to influence nerve repair and functional recovery. In the current study, we determined the effects of two different treatments on the functional and morphological recovery after median and ulnar nerve injury. Adult Wistar male rats weighing 280 to 330 g at the time of surgery (N = 8-10 animals/group) were submitted to nerve crush and 1 week later began a 3-week course of motor rehabilitation involving either "skilled" (reaching for small food pellets) or "unskilled" (walking on a motorized treadmill) training. During this period, functional recovery was monitored weekly using staircase and cylinder tests. Histological and morphometric nerve analyses were used to assess nerve regeneration at the end of treatment. The functional evaluation demonstrated benefits of both tasks, but found no difference between them (P > 0.05). The unskilled training, however, induced a greater degree of nerve regeneration as evidenced by histological measurement (P < 0.05). These data provide evidence that both of the forelimb training tasks used in this study can accelerate functional recovery following brachial plexus injury.

Effect of skilled and unskilled training on nerve regeneration and functional recovery.

The most disabling aspect of human peripheral nerve injuries, the majority of which affect the upper limbs, is the loss of skilled hand movements. Activity-induced morphological and electrophysiological remodeling of the neuromuscular junction has been shown to influence nerve repair and functional recovery. In the current study, we determined the effects of two different treatments on the functional and morphological recovery after median and ulnar nerve injury. Adult Wistar male rats weighing 280 to 330 g at the time of surgery (N = 8-10 animals/group) were submitted to nerve crush and 1 week later began a 3-week course of motor rehabilitation involving either "skilled" (reaching for small food pellets) or "unskilled" (walking on a motorized treadmill) training. During this period, functional recovery was monitored weekly using staircase and cylinder tests. Histological and morphometric nerve analyses were used to assess nerve regeneration at the end of treatment. The functional evaluation demonstrated benefits of both tasks, but found no difference between them (P > 0.05). The unskilled training, however, induced a greater degree of nerve regeneration as evidenced by histological measurement (P < 0.05). These data provide evidence that both of the forelimb training tasks used in this study can accelerate functional recovery following brachial plexus injury.

Viability of mesenchymal stem cells during electrospinning

Tissue engineering is a technique by which a live tissue can be re-constructed and one of its main goals is to associate cells with biomaterials. Electrospinning is a technique that facilitates the production of nanofibers and is commonly used to develop fibrous scaffolds to be used in tissue engineering. In the present study, a different approach for cell incorporation into fibrous scaffolds was tested. Mesenchymal stem cells were extracted from the wall of the umbilical cord and mononuclear cells from umbilical cord blood. Cells were re-suspended in a 10 percent polyvinyl alcohol solution and subjected to electrospinning for 30 min under a voltage of 21 kV. Cell viability was assessed before and after the procedure by exclusion of dead cells using trypan blue staining. Fiber diameter was observed by scanning electron microscopy and the presence of cells within the scaffolds was analyzed by confocal laser scanning microscopy. After electrospinning, the viability of mesenchymal stem cells was reduced from 88 to 19.6 percent and the viability of mononuclear cells from 99 to 8.38 percent. The loss of viability was possibly due to the high viscosity of the polymer solution, which reduced the access to nutrients associated with electric and mechanical stress during electrospinning. These results suggest that the incorporation of cells during fiber formation by electrospinning is a viable process that needs more investigation in order to find ways to protect cells from damage.

Transplantation of mononuclear cells from human umbilical cord blood promotes functional recovery after traumatic spinal cord injury in Wistar rats

Cell transplantation is a promising experimental treatment for spinal cord injury. The aim of the present study was to evaluate the efficacy of mononuclear cells from human umbilical cord blood in promoting functional recovery when transplanted after a contusion spinal cord injury. Female Wistar rats (12 weeks old) were submitted to spinal injury with a MASCIS impactor and divided into 4 groups: control, surgical control, spinal cord injury, and one cell-treated lesion group. Mononuclear cells from umbilical cord blood of human male neonates were transplanted in two experiments: a) 1 h after surgery, into the injury site at a concentration of 5 x 10(6) cells diluted in 10 µL 0.9 percent NaCl (N = 8-10 per group); b) into the cisterna magna, 9 days after lesion at a concentration of 5 x 10(6) cells diluted in 150 µL 0.9 percent NaCl (N = 12-14 per group). The transplanted animals were immunosuppressed with cyclosporin-A (10 mg/kg per day). The BBB scale was used to evaluate motor behavior and the injury site was analyzed with immunofluorescent markers to label human transplanted cells, oligodendrocytes, neurons, and astrocytes. Spinal cord injury rats had 25 percent loss of cord tissue and cell treatment did not affect lesion extension. Transplanted cells survived in the injured area for 6 weeks after the procedure and both transplanted groups showed better motor recovery than the untreated ones (P < 0.05). The transplantation of mononuclear cells from human umbilical cord blood promoted functional recovery with no evidence of cell differentiation.

Transplantation of mononuclear cells from human umbilical cord blood promotes functional recovery after traumatic spinal cord injury in Wistar rats.

Cell transplantation is a promising experimental treatment for spinal cord injury. The aim of the present study was to evaluate the efficacy of mononuclear cells from human umbilical cord blood in promoting functional recovery when transplanted after a contusion spinal cord injury. Female Wistar rats (12 weeks old) were submitted to spinal injury with a MASCIS impactor and divided into 4 groups: control, surgical control, spinal cord injury, and one cell-treated lesion group. Mononuclear cells from umbilical cord blood of human male neonates were transplanted in two experiments: a) 1 h after surgery, into the injury site at a concentration of 5 x 10(6) cells diluted in 10 µL 0.9% NaCl (N = 8-10 per group); b) into the cisterna magna, 9 days after lesion at a concentration of 5 x 10(6) cells diluted in 150 µL 0.9% NaCl (N = 12-14 per group). The transplanted animals were immunosuppressed with cyclosporin-A (10 mg/kg per day). The BBB scale was used to evaluate motor behavior and the injury site was analyzed with immunofluorescent markers to label human transplanted cells, oligodendrocytes, neurons, and astrocytes. Spinal cord injury rats had 25% loss of cord tissue and cell treatment did not affect lesion extension. Transplanted cells survived in the injured area for 6 weeks after the procedure and both transplanted groups showed better motor recovery than the untreated ones (P < 0.05). The transplantation of mononuclear cells from human umbilical cord blood promoted functional recovery with no evidence of cell differentiation.

Viability of mesenchymal stem cells during electrospinning.

Tissue engineering is a technique by which a live tissue can be re-constructed and one of its main goals is to associate cells with biomaterials. Electrospinning is a technique that facilitates the production of nanofibers and is commonly used to develop fibrous scaffolds to be used in tissue engineering. In the present study, a different approach for cell incorporation into fibrous scaffolds was tested. Mesenchymal stem cells were extracted from the wall of the umbilical cord and mononuclear cells from umbilical cord blood. Cells were re-suspended in a 10% polyvinyl alcohol solution and subjected to electrospinning for 30 min under a voltage of 21 kV. Cell viability was assessed before and after the procedure by exclusion of dead cells using trypan blue staining. Fiber diameter was observed by scanning electron microscopy and the presence of cells within the scaffolds was analyzed by confocal laser scanning microscopy. After electrospinning, the viability of mesenchymal stem cells was reduced from 88 to 19.6% and the viability of mononuclear cells from 99 to 8.38%. The loss of viability was possibly due to the high viscosity of the polymer solution, which reduced the access to nutrients associated with electric and mechanical stress during electrospinning. These results suggest that the incorporation of cells during fiber formation by electrospinning is a viable process that needs more investigation in order to find ways to protect cells from damage.

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.

Effects of global cerebral ischemia and preconditioning on heat shock protein 27 immunocontent and phosphorylation in rat hippocampus.

Global cerebral ischemia, with or without preconditioning, leads to an increase in heat shock protein 27 (HSP27) immunocontent and alterations in HSP27 phosphorylation in CA1 and dentate gyrus areas of the hippocampus. We studied different times of reperfusion (1, 4, 7, 14, 21 and 30 days) using 2 min, 10 min or 2+10 min of ischemia. The results showed an increase in HSP27 immunocontent of about 300% after 10 min of ischemia in CA1 and dentate gyrus. CA1, a hippocampal vulnerable area, showed an increase in HSP27 phosphorylation, parallel with immunocontent. In dentate gyrus, a resistant area, the increase in HSP phosphorylation was lower than immunocontent. After preconditioned ischemia (2+10 min), when CA1 neurons are protected to a lethal, 10 min insult, we observed an increase in HSP immunocontent and a decrease in phosphorylation in both regions of the hippocampus, suggesting that, when there is no neuronal death, HSP27 in a vulnerable area responds similarly to the resistant area.When dephosphorylated, HSP27 acts as a chaperone, protecting other proteins from denaturation. As it is markedly expressed in astrocytes, we suggest that HSP27 could be protecting hippocampal astrocytes, which could then be helping neurons to resist to the insult, maintaining tissue normal homeostasis.

In vivo and in vitro effect of imipramine and fluoxetine on Na+,K+-ATPase activity in synaptic plasma membranes from the cerebral cortex of rats.

The effects of in vivo chronic treatment and in vitro addition of imipramine, a tricyclic antidepressant, or fluoxetine, a selective serotonin reuptake inhibitor, on the cortical membrane-bound Na+,K+-ATPase activity were studied. Adult Wistar rats received daily intraperitoneal injections of 10 mg/kg of imipramine or fluoxetine for 14 days. Twelve hours after the last injection rats were decapitated and synaptic plasma membranes (SPM) from cerebral cortex were prepared to determine Na+,K+-ATPase activity. There was a significant decrease (10%) in enzyme activity after imipramine but fluoxetine treatment caused a significant increase (27%) in Na+,K+-ATPase activity compared to control (P<0.05, ANOVA; N = 7 for each group). When assayed in vitro, the addition of both drugs to SPM of naive rats caused a dose-dependent decrease in enzyme activity, with the maximal inhibition (60-80%) occurring at 0.5 mM. We suggest that a) imipramine might decrease Na+,K+-ATPase activity by altering membrane fluidity, as previously proposed, and b) stimulation of this enzyme might contribute to the therapeutic efficacy of fluoxetine, since brain Na+,K+-ATPase activity is decreased in bipolar patients.

In vivo and in vitro effect of imipramine and fluoxetine on Na+, K+-ATPase activity in synaptic plasma membranes from the cerebral cortex of rats

The effects of in vivo chronic treatment and in vitro addition of imipramine, a tricyclic antidepressant, or fluoxetine, a selective serotonin reuptake inhibitor, on the cortical membrane-bound Na+,K+-ATPase activity were studied. Adult Wistar rats received daily intraperitoneal injections of 10 mg/kg of imipramine or fluoxetine for 14 days. Twelve hours after the last injection rats were decapitated and synaptic plasma membranes (SPM) from cerebral cortex were prepared to determine Na+,K+-ATPase activity. There was a significant decrease (10 percent) in enzyme activity after imipramine but fluoxetine treatment caused a significant increase (27 percent) in Na+,K+-ATPase activity compared to control (P<0.05, ANOVA; N = 7 for each group). When assayed in vitro, the addition of both drugs to SPM of naive rats caused a dose-dependent decrease in enzyme activity, with the maximal inhibition (60-80 percent) occurring at 0.5 mM. We suggest that a) imipramine might decrease Na+,K+-ATPase activity by altering membrane fluidity, as previously proposed, and b) stimulation of this enzyme might contribute to the therapeutic efficacy of fluoxetine, since brain Na+,K+-ATPase activity is decreased in bipolar patients