Postinjury magnesium sulfate treatment is not markedly neuroprotective for striatal medium spiny neurons after perinatal hypoxia/ischemia in the rat

The Role of the Thioredoxin System in Brain Diseases

The thioredoxin system, consisting of thioredoxin (Trx), thioredoxin reductase (TrxR), and NADPH, plays a fundamental role in the control of antioxidant defenses, cell proliferation, redox states, and apoptosis. Aberrations in the Trx system may lead to increased oxidative stress toxicity and neurodegenerative processes. This study reviews the role of the Trx system in the pathophysiology and treatment of Alzheimer's, Parkinson's and Huntington's diseases, brain stroke, and multiple sclerosis. Trx system plays an important role in the pathophysiology of those disorders via multiple interactions through oxidative stress, apoptotic, neuro-immune, and pro-survival pathways. Multiple aberrations in Trx and TrxR systems related to other redox systems and their multiple reciprocal relationships with the neurodegenerative, neuro-inflammatory, and neuro-oxidative pathways are here analyzed. Genetic and environmental factors (nutrition, metals, and toxins) may impact the function of the Trx system, thereby contributing to neuropsychiatric disease. Aberrations in the Trx and TrxR systems could be a promising drug target to prevent and treat neurodegenerative, neuro-inflammatory, neuro-oxidative stress processes, and related brain disorders.

Current Therapies for Neonatal Hypoxic-Ischaemic and Infection-Sensitised Hypoxic-Ischaemic Brain Damage

Neonatal hypoxic-ischaemic brain damage is a leading cause of child mortality and morbidity, including cerebral palsy, epilepsy, and cognitive disabilities. The majority of neonatal hypoxic-ischaemic cases arise as a result of impaired cerebral perfusion to the foetus attributed to uterine, placental, or umbilical cord compromise prior to or during delivery. Bacterial infection is a factor contributing to the damage and is recorded in more than half of preterm births. Exposure to infection exacerbates neuronal hypoxic-ischaemic damage thus leading to a phenomenon called infection-sensitised hypoxic-ischaemic brain injury. Models of neonatal hypoxia-ischaemia (HI) have been developed in different animals. Both human and animal studies show that the developmental stage and the severity of the HI insult affect the selective regional vulnerability of the brain to damage, as well as the subsequent clinical manifestations. Therapeutic hypothermia (TH) is the only clinically approved treatment for neonatal HI. However, the number of HI infants needed to treat with TH for one to be saved from death or disability at age of 18-22 months, is approximately 6-7, which highlights the need for additional or alternative treatments to replace TH or increase its efficiency. In this review we discuss the mechanisms of HI injury to the immature brain and the new experimental treatments studied for neonatal HI and infection-sensitised neonatal HI.

Delayed Double Treatment with Adult-Sourced Adipose-Derived Mesenchymal Stem Cells Increases Striatal Medium-Spiny Neuronal Number, Decreases Striatal Microglial Number, and Has No Subventricular Proliferative Effect, after Acute Neonatal Hypoxia-Ischemia in Male Rats

Perinatal hypoxia-ischemia (HI) is a major cause of striatal injury. Delayed post-treatment with adult-sourced bone marrow-derived mesenchymal stem cells (BMSCs) increased the absolute number of striatal medium-spiny neurons (MSNs) following perinatal HI-induced brain injury. Yet extraction of BMSCs is more invasive and difficult compared to extraction of adipose-derived mesenchymal stem cells (AD-MSCs), which are easily sourced from subcutaneous tissue. Adult-sourced AD-MSCs are also superior to BMSCs in the treatment of adult ischemic stroke. Therefore, we investigated whether delayed post-treatment with adult-sourced AD-MSCs increased the absolute number of striatal MSNs following perinatal HI-induced brain injury. This included investigation of the location of injected AD-MSCs within the brain, which were widespread in the dorsolateral subventricular zone (dlSVZ) at 1 day after their injection. Cells extracted from adult rat tissue were verified to be stem cells by their adherence to tissue culture plastic and their expression of specific ‘cluster of differentiation’ (CD) markers. They were verified to be AD-MSCs by their ability to differentiate into adipocytes and osteocytes in vitro. Postnatal day (PN) 7/8, male Sprague-Dawley rats were exposed to either HI right-sided brain injury or no HI injury. The HI rats were either untreated (HI + Diluent), single stem cell-treated (HI + MSCs×1), or double stem cell-treated (HI + MSCs×2). Control rats that were matched-for-weight and litter had no HI injury and were treated with diluent (Uninjured + Diluent). Treatment with AD-MSCs or diluent occurred either 7 days, or 7 and 9 days, after HI. There was a significant increase in the absolute number of striatal dopamine and cyclic AMP-regulated phosphoprotein (DARPP-32)-positive MSNs in the double stem cell-treated (HI + MSCs×2) group and the normal control group compared to the HI + Diluent group at PN21. We therefore investigated two potential mechanisms for this effect of double-treatment with AD-MSCs. Specifically, did AD-MSCs: (i) increase the proliferation of cells within the dlSVZ, and (ii) decrease the microglial response in the dlSVZ and striatum? It was found that a primary repair mechanism triggered by double treatment with AD-MSCs involved significantly decreased striatal inflammation. The results may lead to the development of clinically effective and less invasive stem cell therapies for neonatal HI brain injury.

Fetal Neuroprotective Strategies: Therapeutic Agents and Their Underlying Synaptic Pathways

Synaptic signaling is integral for proper brain function. During fetal development, exposure to inflammation or mild hypoxic-ischemic insult may lead to synaptic changes and neurological damage that impairs future brain function. Preterm neonates are most susceptible to these deleterious outcomes. Evaluating clinically used and novel fetal neuroprotective measures is essential for expanding treatment options to mitigate the short and long-term consequences of fetal brain injury. Magnesium sulfate is a clinical fetal neuroprotective agent utilized in cases of imminent preterm birth. By blocking N-methyl-D-aspartate receptors, magnesium sulfate reduces glutamatergic signaling, which alters calcium influx, leading to a decrease in excitotoxicity. Emerging evidence suggests that melatonin and N-acetyl-L-cysteine (NAC) may also serve as novel putative fetal neuroprotective candidates. Melatonin has important anti-inflammatory and antioxidant properties and is a known mediator of synaptic plasticity and neuronal generation. While NAC acts as an antioxidant and a precursor to glutathione, it also modulates the glutamate system. Glutamate excitotoxicity and dysregulation can induce perinatal preterm brain injury through damage to maturing oligodendrocytes and neurons. The improved drug efficacy and delivery of the dendrimer-bound NAC conjugate provides an opportunity for enhanced pharmacological intervention. Here, we review recent literature on the synaptic pathways underlying these therapeutic strategies, discuss the current gaps in knowledge, and propose future directions for the field of fetal neuroprotective agents.

Long-Term Fine Motor Capability on the Staircase Test Correlates with the Absolute Number, but Not the Density, of DARPP-Positive Neurons in the Caudate-Putamen

Measurement of long-term functional and anatomical outcomes in the same animal is considered a powerful strategy for correlating structure with function. In a neonatal animal model of hypoxic-ischemic brain injury that is relevant to cerebral palsy, long-term functional deficits on the staircase test and long-term anatomical deficits in the absolute number of medium-spiny projection neurons in the caudate-putamen were reported in different animals due to logistical constraints. Here, we investigated if these functional and anatomical measures were correlated when measured in the same animals. The medium-spiny projection neurons were investigated because (1) they comprise the vast majority (>97%) of all neurons in the caudate-putamen and (2) motor deficits observed during staircase testing are likely to involve these striatal medium-spiny projection neurons through their connections. We found that long-term skilled forepaw capability on the staircase test was correlated with the absolute number of DARPP-32-positive medium-spiny projection neurons in the caudate-putamen. Specifically, deficits in skilled forepaw ability for the number of sugar pellets eaten and retrieved, and for the maximum staircase level reached, were significantly correlated with a lower absolute neuronal number. We also found that skilled forepaw ability on the staircase test was not correlated with the neuronal density (i.e., number per unit volume) of DARPP-32-positive medium-spiny projection neurons. Since neuronal density is an indirect measure of neuronal survival that is used in the literature, and absolute neuronal number is a direct measure, the results also highlight the scientific value of measuring absolute neuronal number. Anat Rec, 302:2040-2048, 2019. © 2019 American Association for Anatomy.

Magnesium induces preconditioning of the neonatal brain via profound mitochondrial protection

Magnesium sulphate (MgSO₄) given to women in preterm labor reduces cerebral palsy in their offspring but the mechanism behind this protection is unclear, limiting its effective, safe clinical implementation. Previous studies suggest that MgSO₄ is not neuroprotective if administered during or after the insult, so we hypothesised that MgSO₄ induces preconditioning in the immature brain. Therefore, we administered MgSO₄ at various time-points before/after unilateral hypoxia-ischemia (HI) in seven-day-old rats. We found that MgSO₄ treatment administered as a bolus between 6 days and 12 h prior to HI markedly reduced the brain injury, with maximal protection achieved by 1.1 mg/g MgSO₄ administered 24 h before HI. As serum magnesium levels returned to baseline before the induction of HI, we ascribed this reduction in brain injury to preconditioning. Cerebral blood flow was unaffected, but mRNAs/miRNAs involved in mitochondrial function and metabolism were modulated by MgSO₄. Metabolomic analysis (H⁺-NMR) disclosed that MgSO₄ attenuated HI-induced increases in succinate and prevented depletion of high-energy phosphates. MgSO₄ pretreatment preserved mitochondrial respiration, reducing ROS production and inflammation after HI. Therefore, we propose that MgSO₄ evokes preconditioning via induction of mitochondrial resistance and attenuation of inflammation.

Magnesium sulphate induces preconditioning in preterm rodent models of cerebral hypoxia-ischemia

BACKGROUND

Brain injury in preterm infants represents a substantial clinical problem associated with development of motor impairment, cognitive deficits and psychiatric problems. According to clinical studies, magnesium sulphate (MgSO₄) given to women in preterm labor reduces the risk of cerebral palsy in the offspring but the mechanisms behind its neuroprotective effects are still unclear. Our aim was to explore whether MgSO₄ induces tolerance (preconditioning) in the preterm rodent brain. For this purpose we established a model of perinatal hypoxia-ischemia (HI) in postnatal day 4 rats and also applied a recently developed postnatal day 5 mouse model of perinatal brain injury.

METHODS

Postnatal day 4 Wistar rats were exposed to unilateral carotid artery ligation followed by 60, 70 or 80 min of hypoxia (8% O₂). On postnatal day 11, brains were collected and macroscopically visible damage as well as white and grey matter injury was examined using immunohistochemical staining. Once the model had been established, a possible preconditioning protection induced by a bolus MgSO₄ injection prior to 80 min HI was examined 7 days after the insult. Next, a MgSO₄ bolus was injected in C57Bl6 mice on PND 4 followed by exposure to unilateral carotid artery ligation and hypoxia, (10% O₂) for 70 min on PND 5. Brains were collected 7 days after the insult and examined with immunohistochemistry for grey and white matter injury.

RESULTS

In rats, a 60 min period of hypoxia resulted in very few animals with brain injury and although 70 min of hypoxia resulted in a higher percentage of injured animals, the brains were marginally damaged. An 80 min exposure of hypoxia caused cortical tissue damage combined with hippocampal atrophy and neuronal loss in the C3 hippocampal layer. In the rat model, MgSO₄ (1.1 mg/g administered i.p. 24 h prior to the induction of HI, resulting in a transient serum Mg²⁺ concentration elevation to 4.1 ± 0.2 mmol/l at 3 h post i.p. injection) reduced brain injury by 74% in grey matter and 64% in white matter. In the mouse model, MgSO₄ (0.92 mg/g) i.p. injection given 24 h prior to the HI insult resulted in a Mg²⁺ serum concentration increase reaching 2.7 ± 0.3 mmol/l at 3 h post injection, which conferred a 40% reduction in grey matter injury.

CONCLUSIONS

We have established a postnatal day 4 rat model of HI for the study of preterm brain injury. MgSO₄ provides a marked preconditioning protection both in postnatal day 4 rats and in postnatal day 5 mice.

Marked differences in the number and type of synapses innervating the somata and primary dendrites of midbrain dopaminergic neurons, striatal cholinergic interneurons, and striatal spiny projection neurons in the rat

Elucidating the link between cellular activity and goal-directed behavior requires a fuller understanding of the mechanisms underlying burst firing in midbrain dopaminergic neurons and those that suppress activity during aversive or non-rewarding events. We have characterized the afferent synaptic connections onto these neurons in the rat substantia nigra pars compacta (SNpc) and ventral tegmental area (VTA), and compared these findings with cholinergic interneurons and spiny projection neurons in the striatum. We found that the average absolute number of synapses was three to three and one-half times greater onto the somata of dorsal striatal spiny projection neurons than onto the somata of dopaminergic neurons in the SNpc or dorsal striatal cholinergic interneurons. A similar comparison between populations of dopamine neurons revealed a two times greater number of somatic synapses on VTA dopaminergic neurons than SNpc dopaminergic neurons. The percentage of symmetrical, presumably inhibitory, synaptic inputs on somata was significantly higher on spiny projection neurons and cholinergic interneurons compared with SNpc dopaminergic neurons. Synaptic data on the primary dendrites yielded similar significant differences for the percentage of symmetrical synapses for VTA dopaminergic vs. striatal neurons. No differences in the absolute number or type of somatic synapses were evident for dopaminergic neurons in the SNpc of Wistar vs. Sprague-Dawley rat strains. These data from identified neurons are pivotal for interpreting their electrophysiological responses to afferent activity and for generating realistic computer models of neuronal networks of striatal and midbrain dopaminergic function.

Delayed post-treatment with bone marrow-derived mesenchymal stem cells is neurorestorative of striatal medium-spiny projection neurons and improves motor function after neonatal rat hypoxia-ischemia

Perinatal hypoxia-ischemia is a major cause of striatal injury and may lead to cerebral palsy. This study investigated whether delayed administration of bone marrow-derived mesenchymal stem cells (MSCs), at one week after neonatal rat hypoxia-ischemia, was neurorestorative of striatal medium-spiny projection neurons and improved motor function. The effect of a subcutaneous injection of a high-dose, or a low-dose, of MSCs was investigated in stereological studies. Postnatal day (PN) 7 pups were subjected to hypoxia-ischemia. At PN14, pups received treatment with either MSCs or diluent. A subset of high-dose pups, and their diluent control pups, were also injected intraperitoneally with bromodeoxyuridine (BrdU), every 24h, on PN15, PN16 and PN17. This permitted tracking of the migration and survival of neuroblasts originating from the subventricular zone into the adjacent injured striatum. Pups were euthanized on PN21 and the absolute number of striatal medium-spiny projection neurons was measured after immunostaining for DARPP-32 (dopamine- and cAMP-regulated phosphoprotein-32), double immunostaining for BrdU and DARPP-32, and after cresyl violet staining alone. The absolute number of striatal immunostained calretinin interneurons was also measured. There was a statistically significant increase in the absolute number of DARPP-32-positive, BrdU/DARPP-32-positive, and cresyl violet-stained striatal medium-spiny projection neurons, and fewer striatal calretinin interneurons, in the high-dose mesenchymal stem cell (MSC) group compared to their diluent counterparts. A high-dose of MSCs restored the absolute number of these neurons to normal uninjured levels, when compared with previous stereological data on the absolute number of cresyl violet-stained striatal medium-spiny projection neurons in the normal uninjured brain. For the low-dose experiment, in which cresyl violet-stained striatal medium-spiny neurons alone were measured, there was a lower statistically significant increase in their absolute number in the MSC group compared to their diluent controls. Investigation of behavior in another cohort of animals showed that delayed administration of a high-dose of bone marrow-derived MSCs, at one week after neonatal rat hypoxia-ischemia, improved motor function on the cylinder test. Thus, delayed therapy with a high- or low-dose of adult MSCs, at one week after injury, is effective in restoring the loss of striatal medium-spiny projection neurons after neonatal rat hypoxia-ischemia and a high-dose of MSCs improved motor function.

Magnesium is not consistently neuroprotective for perinatal hypoxia-ischemia in term-equivalent models in preclinical studies: a systematic review

There is an important unmet need to further improve the outcome of neonatal encephalopathy in term infants. Meta-analyses of large controlled trials now suggest that maternal magnesium sulfate (MgSO4) therapy is associated with a reduced risk of cerebral palsy and gross motor dysfunction after premature birth, but that it has no effect on death or disability. Because of this inconsistency, it remains controversial whether MgSO4 is clinically neuroprotective and, thus, it is unclear whether it would be appropriate to test MgSO4 for treatment of encephalopathy in term infants. We therefore systematically reviewed the preclinical evidence for neuroprotection with MgSO4 before or after hypoxic-ischemic encephalopathy (HIE) in term-equivalent perinatal and adult animals. The outcomes were highly inconsistent between studies. Although there were differences in dose and timing of administration, there was evidence that beneficial effects of MgSO4 were associated with confounding mild hypothermia and, strikingly, the studies that included rigorous maintenance of environmental temperature or body temperature consistently suggested a lack of effect. On balance, these preclinical studies suggest that peripherally administered MgSO4 is unlikely to be neuroprotective. Rigorous testing in translational animal models of perinatal HIE is needed before MgSO4 should be considered in clinical trials for encephalopathy in term infants.

Research in people with psychosis risk syndrome: a review of the current evidence and future directions

After decades of research, schizophrenia and related psychotic disorders are still among the most debilitating disorders in medicine. The chronic illness course in most individuals, greater treatment responsiveness during the first episode, progressive gray matter decline during early disease stages, and retrospective accounts of 'prodromal' or early illness signs and symptoms formed the basis for research on the psychosis risk syndrome (PRS), known variably as 'clinical high risk' (CHR), or 'ultra-high risk' (UHR), or 'prodromal'. The pioneering era of research on PRS focused on the development and validation of specific assessment tools and the delineation of high risk criteria. This was followed by the examination of conversion rates in psychosis risk cohorts followed naturalistically, identification of predictors of conversion to psychosis, and investigation of interventions able to abort or delay the development of full psychosis. Despite initially encouraging results concerning the predictive validity of PRS criteria, recent findings of declining conversion rates demonstrate the need for further investigations. Results from intervention studies, mostly involving second-generation antipsychotics and cognitive behavioral therapy, are encouraging, but are currently still insufficient to make treatment recommendations for this early, relatively non-specific illness phase. The next phase of research on PRS, just now beginning, has moved to larger, 'multisite' projects to increase generalizability and to ensure that sufficiently large samples at true risk for psychosis are included. Emphasis in these emerging studies is on: 1) identification of biomarkers for conversion to psychosis; 2) examination of non-antipsychotic, neuroprotective and low-risk pharmacologic and non-pharmacologic interventions; 3) testing of potentially phase-specific interventions; 4) examination of the relationship between treatment response during PRS and prognosis for the course of illness; 5) follow-up of patients who developed schizophrenia despite early interventions and comparison of illness trajectories with patients who did not receive early interventions; 6) characterization of individuals with outcomes other than schizophrenia-spectrum disorders, such as bipolar disorder and remission from PRS, including false positive cases; and 7) assessment of meaningful social and role functioning outcomes. While the research conducted to date has already yielded crucial information, the translation of the concept of a clinically identifiable PRS into clinical practice does not seem justified at this point.

Neonatal rat hypoxia-ischemia: Effect of the anti-oxidant mitoquinol, and S-PBN

BACKGROUND

The production of oxygen free radicals after perinatal hypoxia-ischemia is thought to play a critical role in the pathogenesis of the brain injury. Administration of anti-oxidants may thus be neuroprotective. The aim of the present study was to investigate the effect of a mitochondria-targeted anti-oxidant mitoquinol (mitoQ) administered in the form of the prodrug mitoquinone, and an extracellular anti-oxidant N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN; Aldrich, St Louis, MO, USA), on neuronal survival in the rat striatum after acute perinatal hypoxia-ischemia.

METHODS

Mitoquinone at 17 micromol/L (n = 6) or 51 micromol/L (n = 6), or its diluent (n = 12), was continuously infused over 3 days into the right striatum of Sprague-Dawley rats. Infusion was via an Alzet micro-osmotic pump (Alza, Los Angeles, CA, USA), stereotaxically implanted on postnatal day (PN) 7 under anesthesia. In another experiment, S-PBN (100 mg/kg) (n = 8) or its diluent (n = 8) was administered in six s.c. injections every 12 h from the evening of PN7. Hypoxia-ischemia was induced on PN8 by right common carotid artery ligation under anesthesia, followed 2.5 h later by exposure to 8% oxygen for 1.5 h. On PN14 the pups were euthanased and 40 microm serial sections were cut through the entire striatum. The total number of medium-spiny neurons within the right striatum was stereologically determined using the optical disector/Cavalieri method.

RESULTS

No significant difference was seen in the total number of striatal medium-spiny neurons between the 17 micromol/L or 51 micromol/L mitoQ-treated pups and their respective diluent-treated controls. No significant difference was seen in the total number of striatal medium-spiny neurons between the S-PBN-treated and diluent-treated pups.

CONCLUSION

Solely targeting mitochondrial oxidants with mitoQ, or extracellular oxidants with S-PBN, is not protective for striatal medium-spiny neurons after perinatal hypoxia-ischemia.

Neonatal rat hypoxia-ischemia: long-term rescue of striatal neurons and motor skills by combined antioxidant-hypothermia treatment

Perinatal hypoxia-ischemia can cause long-term neurological and behavioral disability. Recent multicenter clinical trials suggest that moderate hypothermia, within 6 h of birth, offers significant yet incomplete protection. We investigated the effect of combined treatment with the antioxidant N-tert-butyl-(2-sulfophenyl)-nitrone (S-PBN) and moderate hypothermia on long-term neuronal injury and behavioral disability. S-PBN or its diluent was administered 12-hourly to rats from postnatal day (PN) 7 to 10. On PN8, hypoxia-ischemia was induced. Immediately post-hypoxia, additional S-PBN and 6 h of moderate hypothermia or additional diluent and 6 h of normothermia were administered. At 1 week, and at 11 weeks, after hypoxia-ischemia, the absolute number of surviving medium-spiny neurons was measured in the coded right striatum. In a separate experiment, skilled forepaw ability was investigated in coded 9- to 11-week-old rats. Normal, uninjured animals were also tested for motor skills at 9- to 11-weeks-of-age. The combination of S-PBN and moderate hypothermia provided statistically significant short- and long-term protection of the striatal medium-spiny neurons to normal control levels. This combinatorial treatment also preserved fine motor skills to normal control levels. The impressive histological and functional preservation suggests that S-PBN and moderate hypothermia is a safe and attractive combination therapy for perinatal hypoxia-ischemia.

Neuroprotective effect of long-term MgSO4 administration after cerebral hypoxia-ischemia in newborn rats is related to the severity of brain damage

Previous studies have shown contradictory results regarding magnesium-mediated neuroprotection in animal models of perinatal asphyxia. The aim of this study is to investigate the effects of MgSO(4) postasphyxial treatment on hypoxia-ischemia (HI)-induced brain injury in neonatal rats and the possibility that this effect is related to the severity of brain damage. Seven-day-old rats underwent unilateral carotid artery ligation followed by 1 or 2 hours of hypoxia (8% O(2)) and MgSO(4) administration. Adenosine triphosphate/phosphocreatine and glutamate/glutamine measurements and neuropathological evaluation of the hippocampus were used to assess the effects of HI and MgSO(4). HI caused time-dependent changes in energy stores, amino acid concentrations, and brain damage. Administration of MgSO(4) after 1 hour but not after 2 hours of hypoxia resulted in significant prevention of HI-induced brain injury. MgSO(4) administration results in a significant protection against moderate HI-induced brain damage, whereas it fails to offer a similar effect against severe brain damage.

Effect of hypothermic post-treatment on hypoxic-ischemic striatal injury, and normal striatal development, in neonatal rats: a stereological study

Fundamental questions remain about the optimal temperature, duration, and mode of delivery that provide the best striatal neuroprotection from hypothermia after perinatal hypoxia-ischemia. This study used stereological methods to investigate whether a mild (i.e. 2 degrees C) or a moderate (5 degrees C) decrease in whole body temperature, for 6 h immediately postinsult, was neuroprotective for striatal medium-spiny neurons after perinatal hypoxia-ischemia in the rat. This study also investigated whether moderate hypothermia had any effect on normal striatal development. Hypoxia-ischemia or sham hypoxia-ischemia was induced on postnatal day (PN) 7. Pups were kept either normothermic, mildly hypothermic, or moderately hypothermic for 6 h immediately postinsult. The absolute number of striatal medium-spiny neurons was calculated using modern stereological methods. There was no significant difference in the absolute number of medium-spiny neurons in the right striatum after either mild hypothermia or moderate hypothermia. There was also no significant difference in the absolute number of medium-spiny neurons between the control normothermic and the control moderately hypothermic pups. The latter results suggest that moderate hypothermia for 6 h immediately postinsult may be a safe treatment for striatal medium-spiny neurons. Yet, neither mild nor moderate hypothermia alone for 6 h immediately posthypoxia-ischemia is neuroprotective for striatal medium-spiny neurons.

Nonoperative management of spasticity in children

Central to the longitudinal management of childhood hypertonia are nonsurgical treatments. These include physical and occupational therapy, electrical stimulation, orthotics, botulium toxin, and drugs. This manuscripts reviews these treatment modalities as well as evaluation tools available to assess their impact on a child's hypertonia.

Antenatal magnesium sulphate neuroprotection in the preterm infant

Very preterm infants have high rates of neurological impairments and disabilities. These rates have not diminished as the survival rates have improved. Basic science research suggests that magnesium sulphate before birth can be neuroprotective for the preterm fetus. Some, but not all, observational studies in humans also suggest a protective effect of antenatal magnesium sulphate on cerebral palsy. Four randomised controlled trials of antenatal magnesium sulphate have reported long-term neurological effects in surviving infants, but only one of these was designed specifically to evaluate the long-term effects of treatment. These studies found that, overall, antenatal magnesium sulphate therapy had no significant effect on paediatric mortality or neurological outcomes in the first few years of life, including cerebral palsy, but it was found to lower the rate of motor problems at 2 years of age in one study. The role for antenatal magnesium sulphate therapy as a neuroprotective agent for the preterm fetus is not yet established.

Magnesium sulphate reduces cell volume in physiological conditions but not in the cytotoxic oedema during global brain ischemia

PRIMARY OBJECTIVE

To establish the effect of MgSO4 on brain cellular volume during physiological and global ischemia using impedanciometric method.

RESEARCH DESIGN

Impedanciometric measure in the brain before and during global brain ischemia, with or without intravenous infusion of MgSO4.

METHODS AND PROCEDURES

Male Sprague-Dawley rats were anaesthetized (thiobarbital, 60 mg kg-1 i.p.). Ringer solution (n=9) or MgSO4 (n=8; 1 mmol Kg-1) where i.v. isovolumetrically administered. Sub-cortical impedance was recorded before and after the infusion of ringer or MgSO4 and during global cerebral ischemia induced by a cardiopulmonary arrest.

MAIN OUTCOMES AND RESULTS

In non-ischemic conditions, MgSO4 infusion induced higher voltage values than those of ringer infusion (Wilcoxon, Z=2.49; p=0.01). During global cerebral ischemia, the MgSO4 infused animals showed a fast drop of voltages (82%) in the first 5 minutes, 4-fold the values of ringer infused animals (p<0.0001). In the following 15 minutes no differences were found between ringer and MgSO4 infused animals.

CONCLUSIONS

The results suggest that MgSO4 significantly reduced brain cell volume in physiological conditions but not in global brain ischemia.

Anesthetic-mediated protection/preconditioning during cerebral ischemia

Cerebral ischemia is a multi-faceted neurodegenerative pathology that causes cellular injury to neurons within the central nervous system. In light of the underlying mechanisms being elucidated, clinical trials to find possible neuroprotectants to date have failed, thus highlighting the need for new putative targets to offer protection. Recent evidence has clearly shown that anesthetics can confer significant protection and or induce a preconditioning effect against cerebral ischemia-induced injury. This review will focus on the putative protection/preconditioning that is afforded by anesthetics, their possible interaction with GABA(A) and glutamate receptors and two-pore potassium channels. In addition, the interaction with inflammatory, apoptotic and underlying molecular (particularly immediately early genes and inducible nitric oxide synthase etc) pathways, the activation of K(ATP) channels and the ability to provide lasting protection will also be addressed.

Effect of the mitochondrial antioxidant, Mito Vitamin E, on hypoxic-ischemic striatal injury in neonatal rats: a dose-response and stereological study

A mitochondria-targeted antioxidant, Mito Vitamin E (MitoVit E), has previously been shown to prevent mitochondrial oxidative damage. The aim of this study was to investigate the effect of MitoVit E on neuronal survival in the rat striatum after acute perinatal hypoxia-ischemia. Continuous striatal infusion with 4.35 microM, 43.5 microM, or 148 microM of MitoVit E before, during, and after hypoxia-ischemia was not neuroprotective for striatal medium-spiny neurons. Pre- or posttreatment with 435 microM MitoVit E was neurotoxic. These results suggest that MitoVit E is not significantly neuroprotective for striatal medium-spiny neurons after acute perinatal hypoxic-ischemic brain injury. The results also suggest that mitochondrial oxidative damage does not contribute significantly to the death of striatal medium-spiny neurons after perinatal hypoxia-ischemia.

Neurodevelopmental outcome of infants with birth asphyxia treated with magnesium sulfate

BACKGROUND

A neuroprotective effect of MgSO(4) has been shown in some animal models of perinatal hypoxic-ischemic brain damage. The aim of the present paper was to determine whether postnatal MgSO(4) infusion (250 mg/kg per day i.v. for 3 days, in combination with dopamine) is safe in infants with severe birth asphyxia, and also observe effects on neurodevelopmental outcome at 18 months.

METHODS

Inclusion criteria were clinical history consistent with perinatal asphyxia; gestational age at least 37 weeks; 5 min Apgar score < or =6; failure to initiate spontaneous respiration within 10 min after birth; and symptoms of encephalopathy. On each day MgSO(4) was infused over 1 h in combination with dopamine (5 microg/kg per min). Changes in vital signs, clinical course of encephalopathy, laboratory variables, and adverse events were monitored. Infants were followed for 18 months.

RESULTS

Thirty infants were studied. Mean birthweight was 2878 g; mean gestational age, 39.6 weeks, and median 5 min Apgar score, 3. All required endotracheal intubation for resuscitation. Median age at MgSO(4) initiation was 5 h. All infants had moderate or severe hypoxic-ischemic encephalopathy. Mean serum Mg(2+) concentration remained at least 1.3 mmol/L. MgSO(4) caused no change in physiological variables including mean arterial pressure. Two infants died as neonates, while six of 28 survivors had severe neurodevelopmental disability at 18 months; the remaining 22 had no neurodevelopmental disability.

CONCLUSION

Postnatal infusion of MgSO(4) with dopamine caused no change in physiological variables. Deaths and severe sequelae were less frequent than in reported cases with the same grade of hypoxic-ischemic encephalopathy severity, and this treatment may improve neurodevelopmental outcome in infants with severe birth asphyxia.

Clomethiazole: mechanisms underlying lasting neuroprotection following hypoxia-ischemia

Damage after hypoxia-ischemia (HI) is observed in both cortical and subcortical regions. In this study, we employed a "Levine" rat model of HI (left carotid ligation + 1 h global hypoxia on PND-26) and used histological and electrophysiological paradigms to assess the long-term neuroprotective properties of clomethiazole (CMZ; a GABA(A) receptor modulator). Key enzymes involved in inflammation, namely nitric oxide synthase (NOS) and arginase, were also examined to assess potential CMZ mechanisms not involving GABA-R activation. Assessments were carried out 3 and 90 days post-HI. Extensive CNS lesions were evident after HI ipsilaterally at both short- and long-term intervals. CMZ significantly decreased the lesion size at 3 and 90 days (P<0.01; P<0.05). Evoked field potential analyses were used to assess hippocampal CA1 neuronal activity ex vivo. Electrophysiological measurements contralateral to the occlusion revealed impaired neuronal function after HI relative to short- and long-term controls (P<0.001, 3 and 14 days; P<0.01, 90 days), with CMZ treatment providing near complete protection (P<0.001 at 3 and 14 days; P<0.01 at 90 days). Both NOS and arginase activities were significantly increased at 3 days (P<0.01), with arginase remaining elevated at 90 days post-HI (P<0.05) ipsilaterally. CMZ suppressed the HI-induced increase in iNOS and arginase activities (P<0.001; P<0.05). These data provide evidence of long-term functional neuroprotection by CMZ in a model of HI. We further conclude that under conditions of HI, functional deficits are not restricted to the ipsilateral hemisphere and are due, at least in part, to changes in the activity of NOS and arginase.

Continuous low-dose treatment with brain-derived neurotrophic factor or neurotrophin-3 protects striatal medium spiny neurons from mild neonatal hypoxia/ischemia: a stereological study

This study aimed to investigate whether continuous, low-dose, intracerebral infusion of either brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3) could protect against striatal neuronal loss in mild neonatal hypoxic/ischaemic brain injury. Continuous, low-dose, intracerebral treatment is likely to minimise unwanted side effects of a single high dose and lengthen the time window for neuroprotection. A milder, albeit brain damage-inducing, hypoxic/ischaemic injury paradigm was used since this situation is likely to produce the highest survival rates and thus the greatest prevalence. Anaesthetised postnatal day 7 rats were each stereotaxically implanted with a brain infusion kit connected to a micro-osmotic pump. The pump continuously infused either BDNF (4.5 microg/day), NT-3 (12 microg/day), or vehicle solution into the right striatum for 3 days from postnatal day 7. The intrastriatal presence of BDNF or NT-3 was verified immunohistochemically. On postnatal day 8, the rats underwent right common carotid artery ligation followed by hypoxic exposure for 1.5 h. Animals were weighed daily thereafter and killed 1 week later on postnatal day 14. The total number of medium spiny neurons within the right striatum was stereologically determined using an optical disector/Cavalieri combination. Other measures of neuroprotection such as brain weight and striatal infarct volume were also undertaken. BDNF or NT-3 significantly increased the total number of surviving medium spiny neurons by 43% and 33% respectively. This significant neuroprotection was not evident when brain weight, striatal volume, striatal infarct volume, and neuronal density measures for NT-3, were compared. These measures therefore missed the protective effect demonstrated by the total neuronal count. This suggests that stereological measurement of total neuronal number is needed to detect neuroprotection at 1 week after low-dose, continuously infused, neurotrophin treatment and mild hypoxic/ischaemic injury. The results also suggest that lower treatment doses may be more useful than previously thought. BDNF may be particularly useful since it fostered both neuroprotection and normal weight gain. The ability to rescue striatal neurons from death may contribute toward a potential short-term, low-dose neurotrophin treatment for mild perinatal hypoxic/ischaemic brain injury in humans.

Magnesium sulfate therapy is of mild benefit to young rats with kaolin-induced hydrocephalus

Hydrocephalus causes damage to periventricular white matter at least in part through chronic ischemia. Magnesium sulfate (MgSO4) has been shown to be protective in various models of neurologic injury. We hypothesized that this agent would ameliorate the effects of experimental childhood-onset hydrocephalus. Hydrocephalus was induced in 3- and 4-wk-old rats by injection of kaolin into the cisterna magna. Tests of cognitive and motor function were performed on a weekly basis. In a blinded and randomized manner, MgSO4 was administered in two separate experiments (s.c. injection 0.85, 4.1, or 8.2 mM/kg/d), supplemented by osmotic minipump infusion (0.03 mM/d) to prevent low trough levels for 2 wk, beginning 2 wk after induction of hydrocephalus. The brains were then subjected to histopathological and biochemical analyses. With the 4.1 mM/kg/d dose, serum Mg++ levels were elevated transiently from 1.3 to approximately 7 mM/L. We observed statistically significant improvement in gait performance and reduced astroglial reaction. There was also a trend to improved memory performance, but no evidence of increased myelin or synaptic protein content. The 8.2 mM/kg/d dose was associated with sedation and there was no evidence of improvement in any parameter. We conclude that MgSO4 might be mildly protective in experimental hydrocephalus.

The postnatal management of the asphyxiated term infant

Investigations in animal models of hypoxic-ischemic injury have not translated into clinical trials of success because of the complex pathology of hypoxic-ischemic brain injury in neonates, the difficulty in defining the onset and duration and severity of the injury, the underlying predisposing disorders of the mothers or the infant, the side effects of many of the investigational drugs precluded clinical use, and many of the investigational agents interfered with only one step of the cascade of events that lead to brain injury. It is possible that a combination of therapeutic agents, including those that affect different levels of the cascade to cell death, will have the greatest neuroprotective effects. Modest hypothermia postpones secondary energy failure and can prolong the window while pharmacotherapeutic agents can be used. It is possible that in the future, sequential administration of agents or strategies that are initiated in the intrapartum period and continued postnatally will be the optimum method for treating infants who are at highest risk for brain injury following acute hypoxic-ischemic asphyxia.

Randomized controlled trial of magnesium sulfate infusion for severe birth asphyxia

OBJECTIVE

To determine whether postnatal MgSO(4) infusion (250 mg/kg per day) for 3 days is both safe and able to improve outcome in infants with severe birth asphyxia, as had been suggested by a small pilot study.

METHODS

A multicenter randomized controlled trial was conducted. Entry criteria included 5-min Apgar score of seven or less and either failure to initiate spontaneous respiration at 10 min after birth because of asphyxia, or occurrence of clinically apparent seizures within 24 h after birth. Number of subjects was calculated to detect a 50% reduction in incidence of adverse outcomes.

RESULTS

Distributions of perinatal factors, neonatal baseline characteristics and severity of hypoxic-ischemic encephalopathy were similar in treated and control groups. No significant differences were observed in duration of clinical seizures, or need for assisted ventilation. Survival with normal results of cranial computed tomography, electroencephalography and establishment of oral feeding by 14 days of age, was significantly more frequent in the treated group than in the control group (12/17 vs 5/16, P = 0.04). No significant differences in blood pressure, heart rate or respiratory rate were observed between groups.

CONCLUSION

Postnatal MgSO(4) infusion as above is safe and can improve short-term outcome in infants with severe birth asphyxia.

Advances in prevention and treatment of cerebral palsy

In recent years there have been a number of advances in understanding of predisposing and protective factors in the development of cerebral palsy in infants. Multiple gestation births, maternal infection, and maternal and fetal thrombophilic conditions all predispose to the development of CP in the infant. Opportunities for prevention of CP may develop from an improved understanding of these factors and their mechanisms of operation. Similar progress has been made in the evaluation of treatments for CP and the effects of these treatments on the individual's impairment, function, and disability. Selective posterior rhizotomy and Botulinum toxin A are now widely used in the treatment of spasticity. The challenge remains to determine how effectively these promising interventions can alter long-term function and quality of life outcomes in children and adults with CP.

Perinatal brain injury: from pathogenesis to neuroprotection

Brain injury secondary to hypoxic-ischemic disease is the predominant form of all brain injury encountered in the perinatal period. The focus of this article is the most recent research developments in this field and especially those developments that should lead to the most profound effects on interventions in the first years of the new millennium. Neuronal injury is the predominant form of cellular injury in the term infant. The principal mechanisms leading to neuronal death after hypoxia-ischemia/reperfusion are initiated by energy depletion, accumulation of extracellular glutamate, and activation of glutamate receptors. The cascade of events that follows involves accumulation of cytosolic calcium and activation of a variety of calcium-mediated deleterious events. Notably this deleterious cascade, which evolves over many hours, may be interrupted even if interventions are instituted after termination of the insult, an important clinical point. Of the potential interventions, the leading candidates for application to the human infant in the relative short-term are mild hypothermia, inhibitors of free radical production, and free radical scavengers. Promising clinical data are available for the use of mild hypothermia.

Magnesium sulfate treatment after transient hypoxia-ischemia in the newborn piglet does not protect against cerebral damage

Transient perinatal hypoxia-ischemia (HI) can lead to delayed cerebral damage beginning 8-24 h after resuscitation. Cerebroprotective therapies applied soon after HI may thus reduce the severity of brain injury. We have previously shown that MgSO4 administration to newborn piglets after HI fails to prevent the delayed global impairment in cerebral energy metabolism characteristic of severe brain damage. However, high extracellular concentrations of magnesium ions have been found to prevent specific excitotoxic neural cell death in vivo and in vitro. This study therefore examined the hypothesis that MgSO4 administration after HI reduces damage in some regions of the brain even though global energy metabolism is unaffected. Twelve newborn piglets were subjected to global cerebral HI by transient occlusion of both common carotid arteries and reduction of the inspired oxygen fraction to 0.12 until cerebral high-energy phosphates, measured by magnetic resonance spectroscopy, were significantly depleted. Subjects were randomly assigned to two groups of six: the first received MgSO4 (three doses, 400 mg/kg 1 h after resuscitation and 200 mg/kg at 12 and 24 h), and the second received placebo infusions. At 48 h after the start of the experiment, the piglets were killed and their brains were perfused, fixed, and embedded in paraffin wax. Five-micrometer sections were stained with hematoxylin and eosin to allow semiquantitative analysis of the severity and extent of injury to the hippocampus, cerebellum, cerebral cortex, caudate nucleus, thalamus, and striatum and the white matter tracts. There was no difference in the severity of tissue damage between the MgSO4-treated group and the placebo-treated animals in any brain region.

Is Fos protein expressed by dying striatal neurons after immature hypoxic-ischemic brain injury?

The transient induction of mRNA for the immediate-early gene c-fos has been reported following hypoxic-ischemic brain injury in the immature brain. However, no studies have examined the temporal expression of Fos protein, which is the functionally relevant product of c-fos gene expression. Increased expression of Fos protein has been linked to cell death. We therefore examined whether Fos protein is expressed by dying neurons after immature hypoxic-ischemic brain injury. A well characterized immature rat model of hypoxic-ischemic injury at postnatal day (PN) 7 was used. Three hypoxic-ischemic and three normoxic control pups were studied per time point (i.e., 0, 2, 12, 24, 48, and 72 h posttreatment). Expression of Fos within striatal and other neurons was detected immunocytochemically. Fos protein was expressed within dying striatal neurons at 0-12 h after hypoxia-ischemia. However, detection was only seen in 2 of 17 hypoxic-ischemic pups. These 2 pups had >/=80% of their striatal neurons dying within their right, hypoxic-ischemic-exposed hemisphere. Fos protein expression after severe injury may, therefore, be a response to extraordinary or extreme stress. The absence of Fos protein expression in the majority of hypoxic-ischemic pups, which all exhibited striatal neuronal death, suggests that Fos expression is not necessary for cell death to occur. Therapies directed against Fos protein expression may therefore have limited usefulness in immature hypoxic-ischemic brain injury.