Enriched environment and the effect of age on ischemic brain damage

Association between GFAP-positive astrocytes with clinically important parameters including neurological deficits and/or infarct volume in stroke-induced animals

The effect of GFAP-positive astrocytes, as positive or negative factors on stroke complications such as infarct volume and neurological deficits is currently under debate. This review was aimed to evaluate and compare the frequency of studies that showed a positive or negative relationship between astrocyte activation with the improvement of neurological deficits and/or the decrease of infarct volume. In addition, we reviewed two possible causes of differences in results including timepoint of stroke and stroke severity. Time of GFAP assessment was considered as time point and type of stroke induction and duration of stroke as stroke severity. According to our review in the most relevant English-language studies in the PubMed, Web of Science, and Google Scholar databases from 2005 to 2020, the majority of studies (77 vs. 28) showed a negative coincidence or correlation between GFAP-positive cells with neurological improvement as well as between GFAP-positive cells with infarct volume reduction. In most reviewed studies, GFAP expression was reported as a marker related to or coinciding with worse neurological function, or greater infarct volume. However, there were also studies that showed helpful effects of GFAP-positive cells on neurological function or stroke lesion. Although there are some elucidations that the difference in these findings is due to the time point of stroke and stroke severity, our review did not confirm these interpretations.

Laminarin Pretreatment Provides Neuroprotection against Forebrain Ischemia/Reperfusion Injury by Reducing Oxidative Stress and Neuroinflammation in Aged Gerbils

Laminarin is a polysaccharide isolated from brown algae that has various biological and pharmacological activities, such as antioxidant and anti-inflammatory properties. We recently reported that pretreated laminarin exerted neuroprotection against transient forebrain ischemia/reperfusion (IR) injury when we pretreated with 50 mg/kg of laminarin once a day for seven days in adult gerbils. However, there have been no studies regarding a neuroprotective effect of pretreated laminarin against IR injury in aged animals and its related mechanisms. Therefore, in this study, we intraperitoneally inject laminarin (50 mg/kg) once a day to aged gerbils for seven days before IR (5-min transient ischemia) surgery and examine the neuroprotective effect of laminarin treatment and the mechanisms in the gerbil hippocampus. IR injury in vehicle-treated gerbils causes loss (death) of pyramidal neurons in the hippocampal CA1 field at five days post-IR. Pretreatment with laminarin effectively protects the CA1 pyramidal neurons from IR injury. Regarding the laminarin-treated gerbils, production of superoxide anions, 4-hydroxy-2-nonenal expression and pro-inflammatory cytokines [interleukin(IL)-1β and tumor necrosis factor-α] expressions are significantly decreased in the CA1 pyramidal neurons after IR. Additionally, laminarin treatment significantly increases expressions of superoxide dismutase and anti-inflammatory cytokines (IL-4 and IL-13) in the CA1 pyramidal neurons before and after IR. Taken together, these findings indicate that laminarin can protect neurons from ischemic brain injury in an aged population by attenuating IR-induced oxidative stress and neuroinflammation.

Using senses to encourage head and upper limb voluntary movement in young infants: Implications for early intervention

PRIMARY OBJECTIVE

It has long been suggested that a neonate's movement and responses to external stimuli are the product of reflexive reactions rather than purposeful movements. However, several studies have demonstrated that this is not the case. Rationale of literature included: This study seeks to review reports showing that sensory stimuli resulted in newborns recognising and responding to different stimuli with active head or upper limb movements. We also discuss this in the context of current literature about early training on the advancement of movement and brain development. Results and outcomes: Taken together, it is clear that early active experience shapes learning in newborns.

CONCLUSIONS

The impact of this research is most exciting for applications that would induce infants to make purposeful movements, especially as a means for early intervention and rehabilitation for the treatment of infants with or at high risk for developmental delay.

Gender-dependent effects of enriched environment and social isolation in ischemic retinal lesion in adult rats

Exposure to an enriched environment has been shown to have many positive effects on brain structure and function. Numerous studies have proven that enriched environment can reduce the lesion induced by toxic and traumatic injuries. Impoverished environment, on the other hand, can have deleterious effects on the outcome of neuronal injuries. We have previously shown that enriched conditions have protective effects in retinal injury in newborn rats. It is well-known that the efficacy of neuroprotective strategies can depend on age and gender. The aim of the present study, therefore, was to examine the effects of environmental enrichment and social isolation in retinal ischemia. We used bilateral common carotid artery occlusion to induce retinal hypoperfusion in adult Wistar rats of both genders. Groups were housed in standard, enriched or impoverished conditions. Impoverished environment was induced by social isolation. Retinas were processed for histological analysis after two weeks of survival. In the present study, we show that (1) enriched environment has protective effects in adult ischemic retinal lesion, while (2) impoverished environment further increases the degree of ischemic injury, and (3) that these environmental effects are gender-dependent: females are less responsive to the positive effects of environmental enrichment and more vulnerable to retinal ischemia in social isolation. In summary, our present study shows that the effects of both positive and negative environmental stimuli are gender-dependent in ischemic retinal lesions.

Evidence for therapeutic intervention in the prevention of cerebral palsy: hope from animal model research

Knowledge translation, as defined by the Canadian Institute of Health Research, is defined as the exchange, synthesis, and ethically sound application of knowledge--within a complex system of interactions among researchers and users--to accelerate the capture of the benefits of research through improved health, more effective services and products, and a strengthened healthcare system. The requirement for this to occur lies in the ability to continue to determine mechanistic actions at the molecular level, to understand how they fit at the in vitro and in vivo levels, and for disease states, to determine their safety, efficacy, and long-term potential at the preclinical animal model level. In this regard, particularly as it relates to long-term disabilities such as cerebral palsy that begin in utero, but only express their full effect in adulthood, animal models must be used to understand and rapidly evaluate mechanisms of injury and therapeutic interventions. In this review, we hope to provide the reader with a background of animal data upon which therapeutic interventions for the prevention and treatment of cerebral palsy, benefit this community, and increasingly do so in the future.

Impacts of perinatal induced photothrombotic stroke on sensorimotor performance in adult rats

Perinatal ischemic stroke is a leading cerebrovascular disorder occurring in infants around the time of birth associated with long term comorbidities including motor, cognitive and behavioral deficits. We sought to determine the impact of perinatal induced stroke on locomotion, behavior and motor function in rats. A photothrombotic model of ischemic stroke was used in rat at postnatal day 7. Presently, we induced two lesions of different extents, to assess the consequences of stroke on motor function, locomotion and possible correlations to morphological changes. Behavioral tests sensitive to sensorimotor changes were used; locomotion expressed as distance moved in the open field was monitored and histological changes were also assessed. Outcomes depicted two kinds of lesions of different shapes and sizes, relative to laser illumination. Motor performance of rats submitted to stroke was poor when compared to controls; a difference in motor performance was also noted between rats with small and large lesions. Correlations were observed between: motor performance and exposition time; volume ratio and exposition time; and in the rotarod between motor performance and volume ratio. Outcomes demonstrate that photothrombotic cerebral ischemic stroke induced in early postnatal period and tested in adulthood, indeed influenced functional performance governed by the affected brain regions.

Comparison of glial activation in the hippocampal CA1 region between the young and adult gerbils after transient cerebral ischemia

It has been reported that young animals are less vulnerable to brain ischemia. In the present study, we compared gliosis in the hippocampal CA1 region of the young gerbil with those in the adult gerbil induced by 5 min of transient cerebral ischemia by immunohistochemistry and western blot for glial cells. We used male gerbils of postnatal month 1 (PM 1) as the young and PM 6 as the adult. Neuronal death in CA1 pyramidal neurons in the adult gerbil occurred at 4 days post-ischemia; the neuronal death in the young gerbil occurred at 7 days post-ischemia. The findings of glial changes in the young gerbil after ischemic damage were distinctively different from those in the adult gerbil. Glial fibrillary acidic protein-immunoreactive astrocytes, ionized calcium-binding adapter molecule (Iba-1), and isolectin B4-immunoreactive microglia in the ischemic CA1 region were activated much later in the young gerbil than in the adult gerbil. In brief, very less gliosis occurred in the hippocampal CA1 region of the young gerbil than in the adult gerbil after transient cerebral ischemia.

Short-term enrichment makes male rats more attractive, more defensive and alters hypothalamic neurons

Innate behaviors are shaped by contingencies built during evolutionary history. On the other hand, environmental stimuli play a significant role in shaping behavior. In particular, a short period of environmental enrichment can enhance cognitive behavior, modify effects of stress on learned behaviors and induce brain plasticity. It is unclear if modulation by environment can extend to innate behaviors which are preserved by intense selection pressure. In the present report we investigate this issue by studying effects of relatively short (14-days) environmental enrichment on two prominent innate behaviors in rats, avoidance of predator odors and ability of males to attract mates. We show that enrichment has strong effects on both the innate behaviors: a) enriched males were more avoidant of a predator odor than non-enriched controls, and had a greater rise in corticosterone levels in response to the odor; and b) had higher testosterone levels and were more attractive to females. Additionally, we demonstrate decrease in dendritic length of neurons of ventrolateral nucleus of hypothalamus, important for reproductive mate-choice and increase in the same in dorsomedial nucleus, important for defensive behavior. Thus, behavioral and hormonal observations provide evidence that a short period of environmental manipulation can alter innate behaviors, providing a good example of gene-environment interaction.

The effect of postischemic hypothermia on apoptotic cell death in the neonatal rat brain

BACKGROUND AND OBJECTIVE

Hypothermia is the most effective neuroprotective therapy against ischemic injury in the developing brain. However, the mechanism of hypothermic neuroprotection is not well understood. We sought to investigate whether hypothermia mediates neuroprotection by modulating ischemia-induced apoptosis.

METHODS

Seven-day-old rat pups were randomly assigned to either control or hypoxia-ischemia (HI) groups. In the HI group, the internal carotid artery was ligated and cut. This was followed by transient hypoxia at 8% oxygen for 90 min. In the control rats, the internal carotid was isolated but not ligated. Immediately after the hypoxic episode, pups in the HI group were either placed in water baths maintained at 28°C for 24 h (core temperatures at 31°C) or they remained in a normothermic environment. Animals were sacrificed at 24, 48 and 72 h and 1 week after the HI insult. Brain sections were processed for immunohistochemistry and Western blots.

RESULTS

Caspase 3 expression was significantly higher in the core compared with the peri-infarct area at all time points in normothermic rats. Hypothermia reduced caspase 3 expression in the core but had little effect in the peri-infarct area. Hypothermia reduced apoptosis-inducing factor translocation to the nucleus in the core and peri-infarct area. Concurrently, X-linked inhibitor of apoptosis (XIAP) expression was significantly potentiated in the hypothermic-ischemic core but not in the peri-infarct area.

CONCLUSION

Hypothermic modulation of caspase-dependent apoptosis may be mediated by upregulating XIAP. However, the effect of hypothermia on caspase-independent apoptosis may be mediated by XIAP-independent mechanisms. Importantly, these effects are mediated in both the core and the penumbral regions of ischemic lesion.

Perturbed cellular response to brain injury during aging

Old age is associated with an enhanced susceptibility to stroke and poor recovery from brain injury, but the cellular processes underlying these phenomena are only partly understood. Therefore, studying the basic mechanisms underlying structural and functional recovery after brain injury in aged subjects is of considerable clinical interest. Behavioral and cytological analyses of rodents that have undergone experimental injury show that: (a) behaviorally, aged rodents are more severely impaired by ischemia than are young animals, and older rodents also show diminished functional recovery; (b) compared to young animals, aged animals develop a larger infarct area, as well as a necrotic zone characterized by a higher rate of cellular degeneration and a larger number of apoptotic cells; (c) both astrocytes and macrophages are activated strongly and early following stroke in aged rodents; (d) in older animals, the premature, intense cytoproliferative activity following brain injury leads to the precipitous formation of growth-inhibiting scar tissue, a phenomenon amplified by the persistent expression of neurotoxic factors; (e) though the timing is altered, the regenerative capability of the brain is largely preserved in rats, at least into early old age. Whether endogenous neurogenesis contributes to spontaneous recovery after stroke has not yet been established. If neurogenesis from endogenous neuronal stem cells is to be used therapeutically, an individual approach will be required to assess the possible extent of neurogenic response as well as the possibilities to alter this response for functional improvement or prevention of further loss of brain function.

An enriched environment improves sensorimotor function post-ischemic stroke

OBJECTIVE

An enriched environment (EE) refers to conditions that facilitate or enhance sensory, cognitive, motor, and social stimulation relative to standard (laboratory) conditions. Despite numerous published studies investigating this concept in animal stroke models, there is still debate around its efficacy. The authors performed a systematic review and meta-analysis to determine the efficacy of an EE on neurobehavioral scores, learning, infarct size, and mortality in animal models of ischemic stroke.

METHODS

Systematic review of controlled studies of the use of an EE in experimental stroke was conducted. Data extracted were analyzed using weighted mean difference meta-analysis. For pooled tests of neurobehavioral scores, a random effects standardized method was used.

RESULTS

Animals recovering in an EE poststroke had mean neurobehavioral scores 0.9 standard deviations (95% confidence interval [CI] = 0.5-1.3; P < .001) above the mean scores of animals recovering in standard conditions and showed a trend toward improvement in learning (25.1% improvement; 95% CI = 3.7-46.6; P = .02). There was no significant increase in death. Animals exposed to an EE had 8.0% larger infarcts than control animals (95% CI = 1.8-14.1; P = .015).

CONCLUSIONS

The results indicate significant improvements in sensorimotor function with EE poststroke but suggest a small increase in infarct volume. Clarification of the underlying mechanisms requires further study but should not overshadow the observed functional improvements and their application to clinical trials during stroke rehabilitation.

The neurobiology of brain and cognitive reserve: mental and physical activity as modulators of brain disorders

The concept of 'cognitive reserve', and a broader theory of 'brain reserve', were originally proposed to help explain epidemiological data indicating that individuals who engaged in higher levels of mental and physical activity via education, occupation and recreation, were at lower risk of developing Alzheimer's disease and other forms of dementia. Subsequently, behavioral, cellular and molecular studies in animals (predominantly mice and rats) have revealed dramatic effects of environmental enrichment, which involves enhanced levels of sensory, cognitive and motor stimulation via housing in novel, complex environments. Furthermore, increasing levels of voluntary physical exercise, via ad libitum access to running wheels, can have significant effects on brain and behavior, thus informing the relative effects of mental and physical activity. More recently, animal models of brain disorders have been compared under environmentally stimulating and standard housing conditions, and this has provided new insights into environmental modulators and gene-environment interactions involved in pathogenesis. Here, we review animal studies that have investigated the effects of modifying mental and physical activity via experimental manipulations, and discuss their relevance to brain and cognitive reserve (BCR). Recent evidence suggests that the concept of BCR is not only relevant to brain aging, neurodegenerative diseases and dementia, but also to other neurological and psychiatric disorders. Understanding the cellular and molecular mechanisms mediating BCR may not only facilitate future strategies aimed at optimising healthy brain aging, but could also identify molecular targets for novel pharmacological approaches aimed at boosting BCR in 'at risk' and symptomatic individuals with various brain disorders.

Chronic electrical stimulation of the contralesional lateral cerebellar nucleus enhances recovery of motor function after cerebral ischemia in rats

Novel neurorehabilitative strategies are needed to improve motor outcomes following stroke. Based on the disynaptic excitatory projections of the dentatothalamocortical pathway to the motor cortex as well as to anterior and posterior cortical areas, we hypothesize that chronic electrical stimulation of the contralesional dentate (lateral cerebellar) nucleus output can enhance motor recovery after ischemia via augmentation of perilesional cortical excitability. Seventy-five Wistar rats were pre-trained in the Montoya staircase task and subsequently underwent left cerebral ischemia with the 3-vessel occlusion model. All survivors underwent stereotactic right lateral cerebellar nucleus (LCN) implantation of bipolar electrodes. Rats were then randomized to 4 groups: LCN stimulation at 10 pps, 20 pps, 50 pps or sham stimulation, which was delivered for a period of 6 weeks. Performance on the Montoya staircase task was re-assessed over the last 4 weeks of the stimulation period. On the right (contralesional) side, motor performance of the groups undergoing sham, 10 pps, 20 pps and 50 pps stimulation was, respectively, 2.5+/-2.7; 2.1+/-2.5; 6.0+/-3.9 (p<0.01) and 4.5+/-3.5 pellets. There was no difference on the left (ipsilesional) side motor performance among the sham or stimulation groups, varying from 15.9+/-6.7 to 17.2+/-2.1 pellets. We conclude that contralesional chronic electrical stimulation of the lateral cerebellar nucleus at 20 pps but not at 10 or 50 pps improves motor recovery in rats following ischemic strokes. This effect is likely to be mediated by increased perilesional cortical excitability via chronic activation of the dentatothalamocortical pathway.

Virtual enriched environments in paediatric neuropsychological rehabilitation following traumatic brain injury: Feasibility, benefits and challenges

A frequent consequence of traumatic brain injury (TBI) is a significant reduction in patients' cerebral activation/arousal, which clinicians agree is not conducive to optimal rehabilitation outcomes. In the context of paediatric rehabilitation, sustained periods of inactivity are particularly undesirable, as contemporary research has increasingly called into question the Kennard principle that youth inherently promotes greater neural plasticity and functional recovery following TBI. Therefore, the onus to create rehabilitation conditions most conducive to harnessing plasticity falls squarely on the shoulders of clinicians. Having noted the efficacy of environmental enrichment in promoting neural plasticity and positive functional outcomes in the animal literature, some researchers have suggested that the emerging technology of Virtual Reality (VR) could provide the means to increase patients' cerebral activation levels via the use of enriched Virtual Environments (VEs). However, 10 years on, this intuitively appealing concept has received almost no attention from researchers and clinicians alike. This paper overviews recent research on the benefits of enriched environments in the injured brain and identifies the potential and challenges associated with implementing VR-based enrichment in paediatric neuropsychological rehabilitation.