Anti-Nogo-A Antibody Therapy Improves Functional Outcome Following Traumatic Brain Injury.

BACKGROUND: Traumatic brain injury (TBI) can cause sensorimotor deficits, and recovery is slow and incomplete. There are no effective pharmacological treatments for recovery from TBI, but research indicates potential for anti-Nogo-A antibody (Ab) therapy. This Ab neutralizes Nogo-A, an endogenous transmembrane protein that inhibits neuronal plasticity and regeneration. OBJECTIVE: We hypothesized that anti-Nogo-A Ab treatment following TBI results in disinhibited axonal growth from the contralesional cortex, the establishment of new compensatory neuronal connections, and improved function. METHODS: We modeled TBI in rats using the controlled cortical impact method, resulting in focal brain damage and motor deficits like those observed in humans with a moderate cortical TBI. Rats were trained on the skilled forelimb reaching task and the horizontal ladder rung walking task. They were then given a TBI, targeting the caudal forelimb motor cortex, and randomly divided into 3 groups: TBI-only, TBI + Anti-Nogo-A Ab, and TBI + Control Ab. Testing resumed 3 days after TBI and continued for 8 weeks, when rats received an injection of the anterograde neuronal tracer, biotinylated dextran amine (BDA), into the corresponding area contralateral to the TBI. RESULTS: We observed significant improvement in rats that received anti-Nogo-A Ab treatment post-TBI compared to controls. Analysis of BDA-positive axons revealed that anti-Nogo-A Ab treatment resulted in cortico-rubral plasticity to the deafferented red nucleus. Conclusions. Anti-Nogo-A Ab treatment may improve functional recovery via neuronal plasticity to brain areas important for skilled movements, and this treatment shows promise to improve outcomes in humans who have suffered a TBI.

Exposure to 5 cGy 28Si Particles Induces Long-Term Microglial Activation in the Striatum and Subventricular Zone and Concomitant Neurogenic Suppression.

The proposed mission to Mars will expose astronauts to space radiation that is known to adversely affect cognition and tasks that rely on fine sensorimotor function. Space radiation has also been shown to affect the microglial and neurogenic responses in the central nervous system (CNS). We recently reported that a low dose of 5 cGy 600 MeV/n 28Si results in impaired cognition and skilled motor behavior in adult rats. Since these tasks rely at least in part on the proper functioning of the striatum, we examined striatal microglial cells in these same subjects. Using morphometric analysis, we found that 28Si exposure increased activated microglial cells in the striatum. The majority of these striatal Iba1+ microglia were ED1-, indicating that they were in an alternatively activated state, where microglia do not have phagocytic activity but may be releasing cytokines that could negatively impact neuronal function. In the other areas studied, Iba1+ microglial cells were increased in the subventricular zone (SVZ), but not in the dentate gyrus (DG). Additionally, we examined the relationship between the microglial response and neurogenesis. An analysis of new neurons in the DG revealed an increase in doublecortin-positive (DCX+) hilar ectopic granule cells (hEGC) which correlated with Iba1+ cells, suggesting that microglial cells contributed to this aberrant distribution which may adversely affect hippocampal function. Taken together, these results indicate that a single dose of 28Si radiation results in persistent cellular effects in the CNS that may impact astronauts both in the short and long-term following deep space missions.

A Potent Inhibitor of Aminopeptidase P2 Reduces Reperfusion Injury in Models of Myocardial Infarction and Stroke.

During a myocardial infarction or ischemic stroke, blood flow to the heart or brain is partially blocked. This results in reduced delivery of oxygen and nutrients and, ultimately, tissue damage. Initial treatment involves removing the clot and restoring blood flow (reperfusion). However, this treatment is not as effective as one would hope because the reperfusion process itself can cause a different type of damage (reperfusion injury) that contributes up to 50% of the total damage. Bradykinin is an autocoid that is released from blood vessel endothelial cells during ischemia and reperfusion and has the potential to prevent reperfusion injury. However, bradykinin is rapidly inactivated by enzymes on endothelial cells, limiting its beneficial effects. One of these enzymes is aminopeptidase P2. We designed a potent and specific inhibitor of aminopeptidase P2 called ST-115, [(S)-2-mercapto-4-methylpentanoyl]-4(S)-fluoro-Pro-Pro-3(R)-beta-Pro. When ST-115 is administered intravenously at the start of reperfusion, it reduces bradykinin degradation. This increases bradykinin's concentration in the capillaries and enhances its protective effects. We tested ST-115 in a mouse model of myocardial infarction and found that the damaged area of the heart was reduced by 58% compared with mice given saline. In a rat model of ischemic stroke, ST-115 reduced functional deficits in a skilled walking test by 60% and reduced brain edema by 51%. It reduced brain infarct size by 48% in a major subset of rats with small strokes. The results indicate that ST-115 can ameliorate reperfusion injury and can ultimately serve as a therapeutic for acute myocardial infarction and ischemic stroke. SIGNIFICANCE STATEMENT: We have shown that our aminopeptidase P2 inhibitor, ST-115, can reduce tissue injury caused by episodes of ischemia followed by reperfusion. It was successful in rodent models of myocardial infarction and stroke. The clinical use would involve the intravenous administration of ST-115 at the induction of reperfusion. In the case of stroke, the successful technique of thrombectomy could be combined with ST-115 administration to simultaneously reduce both ischemic and reperfusion injury.

Organization of exploratory behavior under dark conditions in female and male rats.

Sexually dimorphic performance has been observed across humans and rodents in many spatial tasks. In general, these spatial tasks do not dissociate the use of environmental and self-movement cues. Previous work has demonstrated a role for self-movement cue processing in organizing open field behavior; however, these studies have not directly compared female and male movement characteristics. The current study examined the organization of open field behavior under dark conditions in female and male rats. Significant differences between female and male rats were observed in the location of stopping behavior relative to a cue and the topography exhibited during lateral movements. In contrast, no sex differences were observed on measures used to detect self-movement cue processing deficits. These results provide evidence that female and male rats are similar in their use of self-movement cues to organize open field behavior; however, other factors may be contributing to differences in performance.

Improved Functional Outcome After Peripheral Nerve Stimulation of the Impaired Forelimb Post-stroke.

Lack of blood flow to the brain, i.e., ischemic stroke, results in loss of nerve cells and therefore loss of function in the effected brain regions. There is no effective treatment to improve lost function except restoring blood flow within the first several hours. Rehabilitation strategies are widely used with limited success. The purpose of this study was to examine the effect of electrical stimulation on the impaired upper extremity to improve functional recovery after stroke. We developed a rodent model using an electrode cuff implant onto a single peripheral nerve (median nerve) of the paretic forelimb and applied daily electrical stimulation. The skilled forelimb reaching test was used to evaluate functional outcome after stroke and electrical stimulation. Anterograde axonal tracing from layer V pyramidal neurons with biotinylated dextran amine was done to evaluate the formation of new neuronal connections from the contralesional cortex to the deafferented spinal cord. Rats receiving electrical stimulation on the median nerve showed significant improvement in the skilled forelimb reaching test in comparison with stroke only and stroke with sham stimulation. Rats that received electrical stimulation also exhibited significant improvement in the latency to initiate adhesive removal from the impaired forelimb, indicating better sensory recovery. Furthermore, axonal tracing analysis showed a significant higher midline fiber crossing index in the cervical spinal cord of rats receiving electrical stimulation. Our results indicate that direct peripheral nerve stimulation leads to improved sensorimotor recovery in the stroke-impaired forelimb, and may be a useful approach to improve post-stroke deficits in human patients.

Skilled movement and posture deficits in rat string-pulling behavior following low dose space radiation (28Si) exposure.

Deep space flight missions beyond the Van Allen belt have the potential to expose astronauts to space radiation which may damage the central nervous system and impair function. The proposed mission to Mars will be the longest mission-to-date and identifying mission critical tasks that are sensitive to space radiation is important for developing and evaluating the efficacy of counter measures. Fine motor control has been assessed in humans, rats, and many other species using string-pulling behavior. For example, focal cortical damage has been previously shown to disrupt the topographic (i.e., path circuity) and kinematic (i.e., moment-to-moment speed) organization of rat string-pulling behavior count to compromise task accuracy. In the current study, rats were exposed to a ground-based model of simulated space radiation (5 cGy 28Silicon), and string-pulling behavior was used to assess fine motor control. Irradiated rats initially took longer to pull an unweighted string into a cage, exhibited impaired accuracy in grasping the string, and displayed postural deficits. Once rats were switched to a weighted string, some deficits lessened but postural instability remained. These results demonstrate that a single exposure to a low dose of space radiation disrupts skilled hand movements and posture, suggestive of neural impairment. This work establishes a foundation for future studies to investigate the neural structures and circuits involved in fine motor control and to examine the effectiveness of counter measures to attenuate the effects of space radiation on fine motor control.

Dentate Gyrus Proliferative Responses After Traumatic Brain Injury and Binge Alcohol in Adult Rats.

BACKGROUND: Traumatic brain injury is a significant public health issue that results in serious disability in survivors. Traumatic brain injury patients are often intoxicated with alcohol when admitted to the hospital; however, it is not clear how acute intoxication affects recovery from a traumatic brain injury. Our group has previously shown that binge alcohol prior to traumatic brain injury resulted in long-term impairment in a fine sensorimotor task that was correlated with a decreased proliferative and neuroblast response from the subventricular zone. However, whether binge alcohol prior to traumatic brain injury affects the proliferative response in the hippocampal dentate gyrus is not yet known. METHODS: Male rats underwent binge alcohol (3 g/kg/day) by gastric gavage for 3 days prior to traumatic brain injury. Cell proliferation was labeled by BrdU injections following traumatic brain injury. Stereological quantification and immunofluorescence confocal analysis of BrdU+ cells in the hippocampal dorsal dentate gyrus was performed at 24 hours, 1 week and 6 weeks post traumatic brain injury. RESULTS: We found that either traumatic brain injury alone or binge alcohol alone significantly increased dentate gyrus proliferation at 24 hours and 1 week. However, a combined binge alcohol and traumatic brain injury regimen resulted in decreased dentate gyrus proliferation at 24 hours post-traumatic brain injury. At the 6 week time point, binge alcohol overall reduced the number of BrdU+ cells. Furthermore, more BrdU+ cells were found in the dentate hilar region of alcohol traumatic brain injury compared to vehicle traumatic brain injury groups. The location and double-labeling of these mismigrated BrdU+ cells was consistent with hilar ectopic granule cells. CONCLUSION: The results from this study showed that pre-traumatic brain injury binge alcohol impacts the injury-induced proliferative response in the dentate gyrus in the short-term and may affect the distribution of newly generated cells in the dentate gyrus in the long-term.

Subventricular zone neural precursor cell responses after traumatic brain injury and binge alcohol in male rats.

Traumatic brain injury (TBI) is a major cause of disability worldwide. Additionally, many TBI patients are intoxicated with alcohol at the time of injury, but the impact of acute intoxication on recovery from brain injury is not well understood. We have previously found that binge alcohol prior to TBI impairs spontaneous functional sensorimotor recovery. However, whether alcohol administration in this setting affects reactive neurogenesis after TBI is not known. This study, therefore, sought to determine the short- and long-term effects of pre-TBI binge alcohol on neural precursor cell responses in the subventricular zone (SVZ) following brain injury in male rats. We found that TBI alone significantly increased proliferation in the SVZ as early as 24 hr after injury. Surprisingly, binge alcohol alone also significantly increased proliferation in the SVZ after 24 hr. However, a combined binge alcohol and TBI regimen resulted in decreased TBI-induced proliferation in the SVZ at 24 hr and 1 week post-TBI. Furthermore, at 6 weeks after TBI, binge alcohol administered at the time of TBI significantly decreased the TBI-induced neuroblast response in the SVZ and the rostral migratory stream (RMS). The results from this study suggest that pre-TBI binge alcohol negatively impacts reparative processes in the brain by decreasing short-term neural precursor cell proliferative responses as well as long-term neuroblasts in the SVZ and RMS.

Nogo-A interacts with TrkA to alter nerve growth factor signaling in Nogo-A-overexpressing PC12 cells.

The Nogo-A protein, originally discovered as a potent myelin-associated inhibitor of neurite outgrowth, is also expressed by certain neurons, especially during development and after injury, but its role in neuronal function is not completely known. In this report, we overexpressed Nogo-A in PC12 cells to use as a model to identify potential neuronal signaling pathways affected by endogenously expressed Nogo-A. Unexpectedly, our results show that viability of Nogo-A-overexpressing cells was reduced progressively due to apoptotic cell death following NGF treatment, but only after 24 h. Inhibitors of neutral sphingomyelinase prevented this loss of viability, suggesting that NGF induced the activation of a ceramide-dependent cell death pathway. Nogo-A over-expression also changed NGF-induced phosphorylation of TrkA at tyrosines 490 and 674/675 from sustained to transient, and prevented the regulated intramembrane proteolysis of p75NTR, indicating that Nogo-A was altering the function of the two neurotrophin receptors. Co-immunoprecipitation studies revealed that there was a physical association between TrkA and Nogo-A which appeared to be dependent on interactions in the Nogo-A-specific region of the protein. Taken together, our results indicate that Nogo-A influences NGF-mediated mechanisms involving the activation of TrkA and its interaction with p75NTR.

Improved functional outcome after chronic stroke with delayed anti-Nogo-A therapy: A clinically relevant intention-to-treat analysis.

Many preclinical treatment strategies for stroke have failed when tested in human trials. Although the reasons for these translation failures are multifactorial, one potential concern is the statistical analysis of the preclinical data. One way to rigorously evaluate new therapies is to use an intention-to-treat analysis in preclinical studies. Therefore, in this study, we set out to evaluate the treatment efficacy of a potential clinically relevant therapeutic agent for stroke, i.e., anti-Nogo-A immunotherapy, using an intention-to-treat analysis. Adult rats were trained on the skilled forelimb reaching task and subsequently underwent an ischemic stroke. Nine weeks later, the rats either received intracerebroventricular anti-Nogo-A antibody, control antibody, or no treatment. Skilled reaching performance was assessed by a non-linear model using both an intention-to-treat and per-protocol analysis. Following testing, dendritic complexity was evaluated in the contralesional and perilesional sensorimotor cortex. Both intention-to-treat and per-protocol analysis showed that anti-Nogo-A immunotherapy resulted in statistically significant improved recovery on the skilled forelimb reaching task, although treatment effect was less (though statistically significant) in the intention-to-treat group. Improved functional performance was not shown to be associated with dendritic changes. In conclusion, this study provides evidence for the importance of using intention-to-treat paradigms in testing preclinical therapeutic strategies.

The Subventricular Zone Response to Stroke Is Not a Therapeutic Target of Anti-Nogo-A Immunotherapy.

Ischemic stroke is a leading cause of adult disability with no pharmacological treatments to promote the recovery of lost function. Neutralizing antibodies against the neurite outgrowth inhibitor Nogo-A have emerged as a promising treatment for subacute and chronic stroke in animal models; however, whether anti-Nogo-A treatment affects poststroke neurogenesis remains poorly understood. In this study, we confirmed expression of Nogo-A by neuroblasts in the adult rat subventricular zone (SVZ), a major neurogenic niche; however, we found no evidence that Nogo-A was expressed at the surface of these cells. In vitro migration assays demonstrated that Nogo-A signaling induced a modest reduction in neuroblast migration speed, while anti-Nogo-A antibodies had no effect on motility properties. Using a permanent distal middle cerebral artery occlusion model of cortical stroke, we found that the number of proliferating cells in the SVZ was unaffected in response to stroke, while neuroblast mobilization from the SVZ toward the stroke lesion correlated positively with lesion size. However, we found no evidence that proliferation or neuroblast mobilization were affected by anti-Nogo-A antibody treatment. Our results suggest that the SVZ is not a therapeutic target of anti-Nogo-A immunotherapy, and contribute to our understanding of the SVZ response to cortical stroke.

Anti-Nogo-A Immunotherapy Does Not Alter Hippocampal Neurogenesis after Stroke in Adult Rats.

Ischemic stroke is a leading cause of adult disability, including cognitive impairment. Our laboratory has previously shown that treatment with function-blocking antibodies against the neurite growth inhibitory protein Nogo-A promotes functional recovery after stroke in adult and aged rats, including enhancing spatial memory performance, for which the hippocampus is critically important. Since spatial memory has been linked to hippocampal neurogenesis, we investigated whether anti-Nogo-A treatment increases hippocampal neurogenesis after stroke. Adult rats were subject to permanent middle cerebral artery occlusion followed 1 week later by 2 weeks of antibody treatment. Cellular proliferation in the dentate gyrus was quantified at the end of treatment, and the number of newborn neurons was determined at 8 weeks post-stroke. Treatment with both anti-Nogo-A and control antibodies stimulated the accumulation of new microglia/macrophages in the dentate granule cell layer, but neither treatment increased cellular proliferation or the number of newborn neurons above stroke-only levels. These results suggest that anti-Nogo-A immunotherapy does not increase post-stroke hippocampal neurogenesis.

Binge ethanol prior to traumatic brain injury worsens sensorimotor functional recovery in rats.

A significant number of patients suffering from traumatic brain injury (TBI) have a high blood alcohol level at the time of injury. Furthermore, drinking alcohol in a binge-like pattern is now recognized as a national problem, leading to a greater likelihood of being injured. Our objective was to determine the consequences of a binge paradigm of alcohol intoxication at the time of TBI on long-term functional outcome using a sensitive test of sensorimotor function. We trained adult, male, Sprague Dawley rats on the skilled forelimb reaching task and then administered a single binge dose of ethanol (2 g/kg, i.p.) or saline for three consecutive days (for a total of 3 doses). One hour after the final ethanol dose, rats underwent a TBI to the sensorimotor cortex corresponding to the preferred reaching forelimb. Animals were then tested for seven weeks on the skilled forelimb reaching task to assess the profile of recovery. We found that the group given ethanol prior to TBI displayed a slower recovery curve with a lower recovery plateau as compared to the control group. Therefore, even a relatively short (3 day) episode of binge alcohol exposure can negatively impact long-term recovery from a TBI, underscoring this significant public health problem.

Evidence for fibroblast growth factor-2 as a mediator of amphetamine-enhanced motor improvement following stroke.

Previously we have shown that addition of amphetamine to physical therapy results in enhanced motor improvement following stroke in rats, which was associated with the formation of new motor pathways from cortical projection neurons of the contralesional cortex. It is unclear what mechanisms are involved, but amphetamine is known to induce the neuronal release of catecholamines as well as upregulate fibroblast growth factor-2 (FGF-2) expression in the brain. Since FGF-2 has been widely documented to stimulate neurite outgrowth, the present studies were undertaken to provide evidence for FGF-2 as a neurobiological mechanism underlying amphetamine-induced neuroplasticity. In the present study rats that received amphetamine plus physical therapy following permanent middle cerebral artery occlusion exhibited significantly greater motor improvement over animals receiving physical therapy alone. Amphetamine plus physical therapy also significantly increased the number of FGF-2 expressing pyramidal neurons of the contralesional cortex at 2 weeks post-stroke and resulted in significant axonal outgrowth from these neurons at 8 weeks post-stroke. Since amphetamine is a known releaser of norepinephrine, in vitro analyses focused on whether noradrenergic stimulation could lead to neurite outgrowth in a manner requiring FGF-2 activity. Primary cortical neurons did not respond to direct stimulation by norepinephrine or amphetamine with increased neurite outgrowth. However, conditioned media from astrocytes exposed to norepinephrine or isoproterenol (a beta adrenergic agonist) significantly increased neurite outgrowth when applied to neuronal cultures. Adrenergic agonists also upregulated FGF-2 expression in astrocytes. Pharmacological analysis indicated that beta receptors and alpha1, but not alpha2, receptors were involved in both effects. Antibody neutralization studies demonstrated that FGF-2 was a critical contributor to neurite outgrowth induced by astrocyte-conditioned media. Taken together the present results suggest that noradrenergic activation, when combined with physical therapy, can improve motor recovery following ischemic damage by stimulating the formation of new neural pathways in an FGF-2-dependent manner.

Kinematic analysis of motor recovery with human adult bone marrow-derived somatic cell therapy in a rat model of stroke.

BACKGROUND: The extent to which pharmaceutical and behavioral therapies following central nervous system injury may either deter or encourage the development of compensatory movement patterns is a topic of considerable interest in neurorehabilitation. However, functional outcome measures alone are relatively insensitive to compensatory changes in movement patterns per se. OBJECTIVE: This study used both functional outcome measures and kinematic analysis of forelimb movements to examine the effects of human adult bone marrow-derived somatic cells (hABM-SCs) on motor recovery in a rat model of stroke. METHODS: Adult male Long-Evans black-hooded rats (n = 12) were trained in a forelimb reaching task and then underwent surgical middle cerebral artery occlusion, producing a stroke that impaired the trained paw. One week poststroke, animals were randomly assigned to either a hABM-SC injection or control injection group. Reaching behaviors were then compared at baseline and at 10 weeks poststroke. RESULTS: Both groups improved their outcome scores during the 10-week recovery period. However, the hABM-SC group recovered significantly more function than controls in terms of the number of pellets retrieved. Furthermore, the control group appeared to improve their functional performance by using compensatory strategies that involved an increased number of trajectory adjustments, whereas the hABM-SC group's kinematics more closely resembled prestroke movement patterns. CONCLUSIONS: This study demonstrates that kinematic measures established in stroke research on humans are also sensitive to performance differences prestroke versus poststroke in the rat model, reinforcing the utility of this method to evaluate treatments that may ultimately translate to patient populations.

Delayed anti-nogo-a therapy improves function after chronic stroke in adult rats.

BACKGROUND AND PURPOSE: we have shown that anti-Nogo-A immunotherapy to neutralize the neurite growth inhibitory protein Nogo-A results in functional improvement and enhanced plasticity after ischemic stroke in the adult rat. The present study investigated whether functional improvement and neuronal plasticity can be induced by this immunotherapy when administered to the chronic stroke-impaired rat. METHODS: adult rats were trained to perform the skilled forelimb reaching test, followed by permanent middle cerebral artery occlusion to impair the preferred forelimb. Nine weeks after stroke, animals showing a profound deficit were randomly distributed to 3 groups: no treatment, control antibody, or anti-Nogo-A antibody (11C7). Animals were tested weekly after stroke surgery and daily after antibody treatment until the end of the study. Biotin dextran amine tracing was injected into the nonlesioned forelimb motor cortex at the end of behavioral testing to determine axonal plasticity. RESULTS: all rats showed similar forelimb impairment before treatment. Animals treated with anti-Nogo-A immunotherapy started to show improvement 3 weeks after treatment. Such improvement became significantly better than stroke-only control and control Ab-treated animals, and persisted to the end of the study. Biotin dextran amine-labeled axonal fiber analysis also showed significant enhanced corticorubral axonal sprouting from the contralesional forelimb motor cortex to the deafferented red nucleus in the anti-Nogo-A immunotherapy rats. CONCLUSIONS: these results indicate that improvement of chronic neurological deficits and enhancement of neuronal plasticity can be induced in the adult rat with anti-Nogo-A immunotherapy, and that this therapy may be used to restore function even when administered long after ischemic brain damage has occurred.

Long-term motor improvement after stroke is enhanced by short-term treatment with the alpha-2 antagonist, atipamezole.

Drugs that increase central noradrenergic activity have been shown to enhance the rate of recovery of motor function in pre-clinical models of brain damage. Less is known about whether noradrenergic agents can improve the extent of motor recovery and whether such improvement can be sustained over time. This study was designed to determine if increasing central noradrenergic tone using atipamezole, an alpha-2 adrenoceptor antagonist, could induce a long-term improvement in motor performance in rats subjected to ischemic brain damage caused by permanent middle cerebral artery occlusion. The importance of pairing physical "rehabilitation" with enhanced noradrenergic activity was also investigated. Atipamezole (1 mg/kg, s.c.) or vehicle (sterile saline) was administered once daily on Days 2-8 post-operatively. Half of each drug group was housed under enriched environment conditions supplemented with daily focused activity sessions while the other half received standard housing with no focused activity. Skilled motor performance in forelimb reaching and ladder rung walking was assessed for 8 weeks post-operatively. Animals receiving atipamezole plus rehabilitation exhibited significantly greater motor improvement in both behavioral tests as compared to vehicle-treated animals receiving rehabilitation. Interestingly, animals receiving atipamezole without rehabilitation exhibited a significant motor improvement in the ladder rung walk test but not the forelimb reaching test. These results suggest that a short-term increase in noradrenergic activity can lead to sustained motor improvement following stroke, especially when paired with rehabilitation.

Cognitive recovery in the aged rat after stroke and anti-Nogo-A immunotherapy.

We have previously shown that immunotherapy directed against the protein Nogo-A leads to recovery on a skilled forelimb reaching task in rats after sensorimotor cortex stroke, which correlated with axonal and dendritic plasticity. Here we investigated anti-Nogo-A immunotherapy as an intervention to improve performance on a spatial memory task in aged rats after stroke, and whether cognitive recovery was correlated with structural plasticity. Aged rats underwent a unilateral distal permanent middle cerebral artery occlusion and one week later were treated with an anti-Nogo-A or control antibody. Nine weeks post-stroke, treated rats and normal aged rats were tested on the Morris water maze task. Following testing rats were sacrificed and brains processed for the Golgi-Cox method. Hippocampal CA3 and CA1 pyramidal and dentate gyrus granule cells were examined for dendritic length and number of branch segments, and CA3 and CA1 pyramidal cells were examined for spine density and morphology. Anti-Nogo-A immunotherapy given one week following stroke in aged rats improved performance on the reference memory portion of the Morris water maze task. However, this improved performance was not correlated with structural changes in the hippocampal neurons examined. Our finding of improved performance on the Morris water maze in aged rats after stroke and treatment with anti-Nogo-A immunotherapy demonstrates the promising therapeutic potential for anti-Nogo-A immunotherapy to treat cognitive deficits after stroke. The identification of sites of axonal and dendritic plasticity in the aged brain after stroke and treatment with anti-Nogo-A immunotherapy is still under investigation.

Motor recovery and axonal plasticity with short-term amphetamine after stroke.

BACKGROUND AND PURPOSE: There is considerable debate regarding the efficacy of amphetamine to facilitate motor recovery after stroke or experimental brain injury. Different drug dosing and timing schedules and differing physical rehabilitation strategies may contribute to outcome variability. The present study was designed to ascertain (1) whether short-term amphetamine could induce long-term functional motor recovery in rats after an ischemic lesion modeling stroke in humans; (2) how different levels of physical rehabilitation interact with amphetamine to enhance forelimb-related functional outcome; and (3) whether motor improvement was associated with axonal sprouting from intact corticoefferent pathways originating in the contralesional forelimb motor cortex. METHODS: After permanent middle cerebral artery occlusion, rats received vehicle or amphetamine during the first postoperative week (2 mg/kg, subcutaneously on Postoperative Days 2, 5, and 8). In both treatment groups, separate cohorts of rats were exposed to different levels of "physical rehabilitation" represented by a control environment, enriched environment, or enriched environment with additional sessions of focused activity. Skilled forelimb performance was assessed using the forelimb reaching task and ladder rung walk test. Anterograde tracing with biotinylated dextran amine was used to assess new fiber outgrowth to denervated motor areas. RESULTS: All treatment groups showed significant motor improvement as compared with control-housed, vehicle-treated animals. However, animals housed in an enriched environment that received amphetamine paired with focused activity sessions performed significantly better than any other treatment group and was the only group to achieve complete motor recovery (ie, reached preoperative performance) by 8 weeks. This recovery was associated with axonal sprouting into deafferentated subcortical areas from contralesional projection neurons. CONCLUSIONS: This study suggests that, after stroke, short-term pairing of amphetamine with sufficiently focused activity is an effective means of inducing long-term improvement in forelimb motor function. The anatomic data suggests that corticoefferent plasticity in the form of axonal sprouting contributes to the maintenance of motor recovery.