Fluoxetine and recovery of motor function after focal ischemia in rats

Norepinephrine depletion facilitates recovery of function after focal ischemia in the rat

Previous studies have suggested that increased norepinephrine plays an important role in recovery of function after brain injury; however, the majority of these studies used drugs that are known to also affect other monoamines to increase or decrease norepinephrine. The purpose of the present study was to determine if norepinephrine is required to promote recovery after ischemia. A form of enriched rehabilitation was used to rehabilitate animals after ischemia and the neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine was used to selectively destroy norepinephrine projections from the locus coeruleus. Three sensorimotor tests were used to evaluate the recovery of the animals. Depletion of norepinephrine improved sensorimotor recovery in standard-housed animals and did not impede recovery in the rehabilitation groups. Dopamine beta hydroxylase staining was used to confirm N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine-depleted terminal norepinephrine levels. The amount of norepinephrine terminal staining negatively correlated with recovery of function in the staircase test after ischemia. In addition, enriched rehabilitation increased, but depletion of norepinephrine had no effect on, brain-derived neurotrophic factor protein levels, which have also been linked to improved recovery of function. Together the above findings question the previously postulated role of norepinephrine in recovery of function after stroke.

CNS-active drugs in aging population at high risk of cerebrovascular events: evidence from preclinical and clinical studies

The recovery process following cerebral insults such as stroke is affected by aging and pharmacotherapy. The use of medication including CNS-active drugs has increased in the elderly during recent years. However, surprisingly little is known about how safe they are with respect to severity of sensorimotor and cognitive impairments or recovery of function following possible cerebrovascular accidents. This review examines the experimental and clinical literature, primarily from 1995 onwards, concerning medication in relation to cerebrovascular events and functional recovery. Special attention is directed to polypharmacy and to new CNS-active drugs, which the elderly are already taking or are prescribed to treat emerging, stroke-induced psychiatric symptoms. The neurobiological mechanisms affected by these drugs are discussed.

A qualitative and quantitative analysis of skilled forelimb reaching impairment following intracerebral hemorrhage in rats

The Montoya staircase test is commonly used to measure skilled forelimb reaching ability in a number of brain injury and disease models, but little has been done to characterize the precise nature of the impairments observed after stroke. The present study used slow motion video-recording to analyze staircase reaching performance both qualitatively and quantitatively, and to precisely determine the components of fine forelimb motor function that are disturbed in the collagenase model of hemorrhagic stroke. Male Sprague-Dawley rats were trained to reach for pellets in the staircase task, and subjected to either striatal hemorrhage induced by microinjections of bacterial collagenase or sham surgery. Reaching performance was recorded and examined before surgery, and 2 and 4 weeks later. Impaired animals made fewer attempts and retrieved less pellets than did shams, especially from the lower steps. Interestingly, impaired animals were less able to retrieve a pellet even when the forepaw made contact with it. Detailed qualitative analysis determined that significant disturbances were most prominent in components of skilled reaching that involved fine manipulation of the distal muscles, especially the wrist and digits. While some components of the reaching impairment were found to partially recover at 4 weeks post-surgery, the impairments in these distal motor movements persisted and there was no significant improvement in overall success. These results suggest that the collagenase model of intracerebral hemorrhage produces a functional impairment that most severely affects fine control of the distal forelimb and paw.

Enriched environment enhances transplanted subventricular zone stem cell migration and functional recovery after stroke

Stroke patients suffer from severe impairments and significant effort is under way to develop therapies to improve functional recovery. Stem cells provide a promising form of therapy to replace neuronal circuits lost to injury. Indeed, previous studies have shown that a variety of stem cell types can provide some functional recovery in animal models of stroke. However, it is unlikely that replacement therapy alone will be sufficient to maximize recovery. The aim of the present study was to determine if rodent stem cell transplants combined with rehabilitation resulted in enhanced functional recovery after focal ischemia in rats. Middle cerebral artery occlusion was induced by injection of the vasoconstrictive peptide endothelin-1 adjacent to the middle cerebral artery. Seven days after stroke the rats received adult neural stem cell transplants isolated from mouse subventricular zone or vehicle injection and then subsequently were housed in enriched or standard conditions. The rats in the enriched housing also had access to running wheels once a week. Enriched housing and voluntary running exercise enhanced migration of transplanted stem cells toward the region of injury after stroke and there was a trend toward increased survival of stem cells. Enrichment also increased the number of endogenous progenitor cells in the subventricular zone of transplanted animals. Finally, functional recovery measured in the cylinder test was facilitated only when the stem cell transplants were combined with enrichment and running exercise 7 days after the transplant. These results suggest that the ability of transplanted stem cells in promoting recovery can be augmented by environmental factors such as rehabilitation.

Changes in the kinematic structure and non-kinematic features of movements during skilled reaching after stroke: a Laban Movement Analysis in two case studies

The purpose of this study was to adapt a universal language for human movement, Laban Movement Analysis (LMA), to capture the kinematic and non-kinematic aspects of movement in a reach-for-food task by subjects whose movements had been affected by stroke. Two control subjects, one stroke subject with internal capsule damage, and one subject with right posterior parietal stroke were video recorded while performing the reaching task. The movements of limb advancement, grasping the food, and limb withdrawal to place the food in the mouth, were notated using LMA. A scale, the Expressive Reaching Scale (ERS), was derived from the notation. All subjects completed the task; however, the stroke subjects displayed abnormalities in both the kinematic and non-kinematic aspects of movements during reaching with either limb. The most extensive impairments were in the contralateral-to-stroke limb and were most severe in the subject with internal capsule damage. The ERS rating scale may be a useful diagnosis and assessment tool.

Rat Models of Upper Extremity Impairment in Stroke

Stroke remains the leading cause of adult disability, with upper extremity motor impairments being the most prominent functional deficit in surviving stroke victims. The development of animal models of upper extremity dysfunction after stroke has enabled investigators to examine the neural mechanisms underlying rehabilitation-dependent motor recovery as well as the efficacy of various adjuvant therapies for enhancing recovery. Much of this research has focused on rat models of forelimb motor function after experimentally induced ischemic or hemorrhagic stroke. This article provides a review of several different methods for inducing stroke, including devascularization, photothrombosis, chemical vasoconstriction, and hemorrhagia. We also describe a battery of sensorimotor tasks for assessing forelimb motor function after stroke. The tasks range from measures of gross motor performance to fine object manipulation and kinematic movement analysis, and we offer a comparison of the sensitivity for revealing motor deficits and the amount of time required to administer each motor test. In addition, we discuss several important methodological issues, including the importance of testing on multiple tasks to characterize the nature of the impairments, establishing stable baseline prestroke motor performance measures, dissociating the effects of acute versus chronic testing, and verifying lesion location and size. Finally, we outline general considerations for conducting research using rat models of stroke and the role that these models should play in guiding clinical trials.

Treatment effects of antidepressants in patients with post-stroke depression: a meta-analysis

BACKGROUND

Appropriate treatment of post-stroke depression (PSD) is critically important, considering the negative impact of PSD. Data regarding the treatment efficacy of antidepressants in patients with PSD are conflicting, and the time-dependent effects of antidepressant treatment in this population are unknown.

OBJECTIVE

To systematically assess treatment effects of antidepressants in patients with PSD, incorporating data from recent studies.

METHODS

A meta-analysis of randomized placebo-controlled trials (RCTs) of antidepressants in patients with PSD was conducted, using published studies from 1984 to 2006. Outcome measures of antidepressant treatment included response rate, depression rating scale scores, recovery of neurologic impairments, and improvements in activities of daily living (ADLs) after stroke. The effect size was presented as rate difference (RD) and weighted mean difference for dichotomous outcomes and continuous outcomes, respectively. Pooled effect sizes were calculated by both fixed-effects and random-effects models.

RESULTS

A total of 1320 patients who met inclusion criteria were identified from 16 RCTs. The pooled response rates in the active and placebo groups were 65.18% (234/359) and 44.37% (138/311), respectively. The pooled RD was 0.23 (95% CI 0.03 to 0.43), indicating a significantly higher response rate in the active group compared with the placebo group. From baseline to endpoint, patients in the active group had significantly greater improvement in depressive symptoms compared with patients in the placebo group. Longer duration of treatment was positively correlated with the degree of improvement in depressive symptoms (Spearman's correlation, [rho] = -0.93, p = 0.001). No consistent evidence was found for positive antidepressant effects on the recovery of neurologic impairments and improvements in ADLs.

CONCLUSIONS

The results of this meta-analysis suggest that use of antidepressants among patients with a diagnosis of PSD is associated with improvement in depressive symptoms. Longer durations of antidepressant treatment may be associated with greater reductions in depressive symptoms.

Neurotransmitters and motor activity: effects on functional recovery after brain injury

There are complex relationships among behavioral experience, brain morphology, and functional recovery of an animal before and after brain injury. A large series of experimental studies have shown that exogenous manipulation of central neurotransmitter levels can directly affect plastic changes in the brain and can modulate the effects of experience and training. These complex relationships provide a formidable challenge for studies aimed at understanding neurotransmitter effects on the recovery process. Experiments delineating norepinephrine-modulated locomotor recovery after injury to the cerebral cortex illustrate the close relationships among neurotransmitter levels, brain plasticity, and behavioral recovery. Understanding the neurobiological processes underlying recovery, and how they might be manipulated, may lead to novel strategies for improving recovery from stroke-related gait impairment in humans.

17β-Estradiol treatment following permanent focal ischemia does not influence recovery of sensorimotor function

The development of therapy to aid poststroke recovery is essential. The female hormone 17beta-estradiol has been shown to promote synaptogenesis; the purpose of this study was to attempt to harness these mechanisms to promote repair and recovery in the peri-infarct zone. Rats were ovariectomized, tested for sensorimotor function, and the middle cerebral artery permanently occluded (MCAO). Infarct volumes were calculated using MRI, and damage was equivalent in all animals prior to implantation of either 17beta-estradiol or placebo pellets. Animals were tested for functional recovery for 28 days and tissue processed for synaptic marker syntaxin immunohistochemistry. The stroke induced a significant behavioral deficit, which persisted out to 28 days, and was not significantly different between 17beta-estradiol and placebo treatment groups. There was no difference in syntaxin immunostaining between groups in either the peri-infarct cortex or in the dendritic CA1 reference region. In conclusion, 17beta-estradiol treatment, delivered poststroke, did not influence recovery of function or synaptogenesis.

Delayed minocycline treatment reduces long-term functional deficits and histological injury in a rodent model of focal ischemia

The absence of effective treatments for stroke presents a critical need for novel strategies that can reduce ischemic injury. Neuroinflammation following focal ischemia induces secondary injury in the region surrounding the insult, thus anti-inflammatory agents are potential neuroprotectants. Minocycline is one such agent possessing neuroprotective properties, however many studies examining minocycline after ischemia have used minimal delays between ischemia and treatment, short survival periods, and lack measures of functional outcome. Such studies do not distinguish whether minocycline provides sustained protection or merely delays cell death. This study was designed to address some of these concerns. Male Sprague-Dawley rats were treated with multiple doses of minocycline (45 mg/kg i.p.) or vehicle beginning 2.5 h after endothelin-1-induced focal ischemia. Measures of forelimb asymmetry and skilled reaching (staircase test) were used to determine functional outcome 7, 15 and 28 days after ischemia. Long-term functional assessment indicates that minocycline provides limited benefit in the staircase test, but confers long-term benefit in the forelimb asymmetry test. Subcortical and whole hemisphere infarct volumes were reduced by 41 and 39% respectively in minocycline-treated animals. Further analysis revealed that minocycline attenuated long-term white matter damage adjacent to the striatal injury core, which correlated with sustained functional benefits. This study indicates that delayed minocycline treatment improves long-term functional outcome which is linked to protection of both white and gray matter.

Focal cerebral ischemia alters the spatio-temporal properties, but not the amount of activity in mice

Cerebral ischemia induces sensorimotor and cognitive dysfunctions in rodents; however, little is known about the changes in the spatio-temporal organization of locomotor activity after ischemia. In this study, we continuously assessed the spatio-temporal properties of locomotor activity in an enclosure (40 cm x 40 cm x 65 cm, arbitrarily divided into 16 zones) with feeding and drinking supplies, and observed the spatio-temporal changes in mice with focal cerebral ischemia. Locomotor tracks were recorded from 3rd to 24th h (total 22 h) after middle cerebral artery occlusion (MCAO) or sham operation. The absolute and relative distance traveled or time spent in different regions was analyzed. We found that there was no significant difference in total traveled distances over 22 h between the two groups. Control mice moved and stayed primarily in feeding and drinking zones, frequently in peripheral but rarely in central zones. However, ischemic mice lost such a property, almost evenly moved and stayed in 16 zones. Mice in both groups were more active (traveled more distances) shortly after they entered the enclosure, while ischemic mice returned to stable levels slower. The traveled distance had a remarkable circadian variation with more locomotion in the night in control mice, but not in ischemic mice. Most of the spatial parameters (ratios) of locomotor activity were closely correlated with the ischemic infarction, neuron densities (in cortex, hippocampal CA1 region and striatum), and typical behavioral assessments (neurological scores and inclined board test). Thus, these findings indicate that focal cerebral ischemia does not alter the amount of locomotor activity in mice, but impairs the spatio-temporal properties-prolonging the initial hyperactivity and losing regionally special distribution of the activity.