Tactile extinction: distinguishing between sensorimotor and motor asymmetries in rats with unilateral nigrostriatal damage

Sensorimotor training promotes functional recovery and somatosensory cortical map reactivation following cervical spinal cord injury

Sensorimotor activity has been shown to play a key role in functional recovery after partial spinal cord injury (SCI). Most studies in rodents have focused on the rehabilitation of hindlimb locomotor functions after thoracic or lumbar SCI, whereas forelimb motor and somatosensory abilities after cervical SCI remain largely uninvestigated, despite the high incidence of such injuries in humans. Moreover, little is known about the neurophysiological substrates of training-induced recovery in supraspinal structures. This study was aimed at evaluating the effects of a training procedure combining both motor and sensory stimulation on behavioral performance and somatosensory cortical map remodeling after cervical (C4-C5) spinal hemisection in rats. This SCI severely impaired both sensory and motor capacities in the ipsilateral limbs. Without training, post-lesion motor capacities gradually improved, whereas forepaw tactile abilities remained impaired. Consistently, no stimulus-evoked responses were recorded within the forepaw representational zone in the primary somatosensory (S1) cortex at 2 months after the SCI. However, our data reveal that with training started from the 7th day post-lesion, a nearly complete recovery (characterized by an early and rapid improvement of motor functions) was associated with a gradual compensation of tactile deficits. Furthermore, the recovery of tactile abilities was correlated with the areal extent of reactivation of S1 cortex forepaw representations. Rehabilitative training promoted post-lesion adaptive plasticity, probably by enhancing endogenous activity within spared spinal and supraspinal circuits and pathways sustaining sensory and motor functions. This study highlights the beneficial effect of sensorimotor training in motor improvement and its critical influence on tactile recovery after SCI.

Sustained sensorimotor impairments after endothelin-1 induced focal cerebral ischemia (stroke) in aged rats

Despite recent advances, stroke remains a leading cause of neurological disability with the vast majority of victims being the elderly, who exhibit more severe neurological deficits and a reduced capacity to recover from these disabilities in comparison to young stroke survivors. The objective of the present study was to develop a model of focal ischemic stroke in aged rats using endothelin-1 (ET-1) to produce low mortality rates as well as reliable, robust sensorimotor deficits that resemble functional impairments associated with stroke in humans. Here, we studied the functional and histological outcome following unilateral ET-1 infusions into the sensorimotor cortex of aged rats (20-23 months old). This procedure resulted in low mortality rates (13.3%) and no loss in body weight one week following surgery. Functional assessment was performed using a number of reliable behavioural tests: staircase test (fine motor function), horizontal ladder (skilled locomotion), bilateral tactile stimulation test (somatosensory function) and cylinder test (postural weight support). Following ET-1 induced stroke, all tests demonstrated large and sustained sensorimotor deficits in both forelimb and hindlimb function that failed to improve over the 28-day testing period. In addition, histological assessment revealed a substantial loss of retrogradely labelled corticospinal neurons in the ipsilesional hemisphere following stroke. Our results establish a model for the use of aged rats in future preclinical studies, which will enhance assessment of the long-term benefit of potential neural repair and regenerative strategies.

Differential tactile and motor recovery and cortical map alteration after C4-C5 spinal hemisection

After incomplete spinal cord injury (SCI), the adult central nervous system is spontaneously capable of substantial reorganizations that can underlie functional recovery. Most studies have focused on intraspinal reorganizations after SCI and not on the correlative cortical remodeling. Yet, differential studies of neural correlates of the recovery of sensory and motor abilities may be conducted by segregating motor and somatosensory representations in distinct and topologically organized primary cortical areas. This study was aimed at evaluating the effects of a cervical (C4-C5) spinal cord hemisection on sensorimotor performances and electrophysiological maps in primary somatosensory (S1) and motor (M1) cortices in adult rats. After SCI, an enduring loss of the affected forepaw tactile sensitivity was paralleled by the abolishment of somatosensory evoked responses in the deprived forepaw area within the S1 cortex. In contrast, severe motor deficits in unilateral forelimb were partially restored over the first postoperative month, despite remnant deficits in distal movement. The overall M1 map size was drastically reduced in SCI rats relative to intact rats. In the remaining M1 map, the shoulder and elbow movements were over-represented, consistent with the behavioral recovery of proximal joint movements in almost all rats. By contrast, residual wrist representations were observed in M1 maps of half of the rats that did not systematically correlate with a behavioral recovery of these joint movements. This study highlights the differential potential of ascending and descending pathways to reorganize after SCI.

The adhesive removal test: a sensitive method to assess sensorimotor deficits in mice

Long-term functional deficits after a brain injury are difficult to assess in the mouse. If no deficit is observed, researchers could conclude either that the animal has fully recovered or that the tests they used were not appropriate or sensitive enough to the modality of the deficits. We present here a detailed protocol describing how to conduct an adhesive removal test for this species. It consists of applying adhesive tape on each forepaw of the animal and measuring the time-to-contact and the time-to-remove them. This behavior implies correct paw and mouth sensitivity (time-to-contact) and correct dexterity (time-to-remove). To decrease interindividual differences, we recommend a training session (1 week, 1 trial per day) before surgical procedures so that mice to reach optimal performances.

Functional testing in a mouse stroke model induced by occlusion of the distal middle cerebral artery

Reducing post-stroke disability is the major goal of stroke therapy. Consequently, functional testing is essential in experimental stroke studies to increase the predictive value of animal models. We used several sensory and motor tests to assess functional disability in a mouse model of permanent distal middle cerebral artery occlusion (pdMCAO) that induced mainly cortical infarcts. Gait dynamics were transiently disturbed after pdMCAO as measured by different analysis techniques. Stance and brake duration were shorter after pdMCAO. Consistent with sensory and motor deficits the latency to move was prolonged up to 14 days after pdMCAO and the performance in the corner test and handedness were affected on day 1 or 2 after pdMCAO. Heart rate was decreased and heart rate variability were increased after pdMCAO indicating sympathetic-parasympathetic imbalance. In summary, pdMCAO-induced cortical infarcts lead to clinically relevant sensory, motor and cardiac autonomic dysfunction in mice. The present study provides a basis to explore the potential of functional testing for neuroprotection and neuroregeneration after stroke.

Striatal neuroprotection with methylene blue

Recent literature indicates that low-dose Methylene Blue (MB), an autoxidizable dye with powerful antioxidant and metabolic enhancing properties, might prevent neurotoxin-induced neural damage and associated functional deficits. This study evaluated whether local MB may counteract the anatomical and functional effects of the intrastriatal infusion of the neurotoxin rotenone (Rot) in the rat. To this end, stereological analyses of striatal lesion volumes were performed and changes in oxidative energy metabolism in the striatum and related motor regions were mapped using cytochrome oxidase histochemistry. The influence of MB on striatal levels of oxidative stress induced by Rot was determined, and behavioral tests were used to investigate the effect of unilateral MB coadministration on motor asymmetry. Rot induced large anatomical lesions resembling "metabolic strokes," whose size was greatly reduced in MB-treated rats. Moreover, MB prevented the decrease in cytochrome oxidase activity and the perilesional increase in oxidative stress associated with Rot infusion in the striatum. MB also prevented the indirect effects of the Rot-induced lesion on cytochrome oxidase activity in related motor regions, such as the striatal regions rostral and caudal to the lesion, the substantia nigra compacta and reticulata, and the pedunculopontine nucleus. At a network level, MB maintained a global strengthening of functional connectivity in basal ganglia-thalamocortical motor circuits, as opposed to the functional decoupling observed in Rot-alone subjects. Finally, MB partially prevented the behavioral sensorimotor asymmetries elicited by Rot. These results are consistent with protective effects of MB against neurotoxic damage in the brain parenchyma. This study provides the first demonstration of the anatomical, metabolic and behavioral neuroprotective effects of MB in the striatum in vivo, and supports the notion that MB could be a valuable intervention against neural damage associated with oxidative stress and energy hypometabolism.

Amphetamine-evoked rotation requires newly synthesized dopamine at 14 days but not 1 day after intranigral 6-OHDA and is consistently dissociated from sensorimotor behavior

Immediately after unilateral, intranigral 6-hydroxydopamine (6-OHDA), amphetamine (AMPH) evokes "paradoxical" contraversive rotation, whereas 14 days later, AMPH evokes the traditional ipsiversive rotation used to model the chronic Parkinsonian state. In this study, the hypothesis was that accelerated dopamine (DA) synthesis ipsilateral to the lesion augments cytoplasmic DA to produce paradoxical rotation. Therefore, the sensitivity to synthesis inhibition of AMPH-evoked rotation at 1 or 14 days after 6-OHDA was assessed. To determine the functional status that might be reflected by paradoxical rotation, sensorimotor abilities were examined at 1 and 14 days following unilateral 6-OHDA using the elevated swing, paw placement, grip strength, ladder walking, somatosensory neglect, and cylinder tests. At 14 days after 6-OHDA when AMPH-evoked ipsiversive rotation is mediated by the intact hemisphere, rotation was dose-dependently reduced by tyrosine hydroxylase (TH) inhibition with alpha-methyl-p-tyrosine (alpha-MPT) or dopa decarboxylase (DDC) inhibition with 3-hydroxybenzyl hydrazine (NSD-1015), indicating dependence upon newly synthesized DA. Conversely, at 1 day after 6-OHDA, paradoxical rotation, presumably mediated by the treated hemisphere, was completely resistant to synthesis blockade, indicating an abundant supply of intracellular DA that is independent from synthesis rates. Sensorimotor behaviors were not correlated with AMPH-evoked rotation. The present data do not support the hypothesis that enhanced DA synthesis is required to express paradoxical rotation. Therefore, alternative mechanisms that may enhance cytoplasmic DA to produce paradoxical rotation are discussed.

Sensorimotor behavioral effects of endothelin-1 induced small cortical infarcts in C57BL/6 mice

Mouse models have not paralleled rat models of stroke in advances in sensitive, species appropriate measures of neurological and behavioral recovery. Most available tests of mouse sensorimotor function are adaptations of those originally developed in rats and may not be as sensitive in detecting behavioral deficits after small cortical lesions in mice. Our purpose was to test the use of a vasoconstricting peptide, endothelin-1 (ET-1), to produce focal infarcts of the mouse sensorimotor cortex and to establish a behavioral test battery sensitive to resulting sensorimotor deficits. Young adult (3-5-month-old) male C57BL/6 mice received intracortical infusions of ET-1 that produced unilateral lesions of the forelimb region of the sensorimotor cortex, intracortical infusions of sterile saline, or sham surgeries. Pre-operatively and at various time points over 3 weeks post-surgery, they were administered a test battery that included measures of sensorimotor asymmetry (Corner and Bilateral Tactile Stimulation Tests), coordinated forepaw use (Cylinder and Ladder Rung Tests), and dexterous forepaw function (Pasta Matrix Reaching Test). ET-1 infusions resulted in consistently placed, focal cortical infarcts and forelimb impairments as measured with the Ladder Rung, Bilateral Tactile Stimulation, and Pasta Matrix Reaching Tests. On the Bilateral Tactile Stimulation and Pasta Matrix Reaching Tests, impairments persisted throughout the time span of observation (26 days). These results support ET-1 as a viable option for creating small, reproducible lesions of anatomical subregions in the mouse neocortex that result in lasting functional impairments in the forelimb, as observed with sufficiently sensitive measures.

Mucosal tolerance to E-selectin promotes the survival of newly generated neuroblasts via regulatory T-cell induction after stroke in spontaneously hypertensive rats

Neuroblasts in the subventricular zone (SVZ) proliferate markedly after brain ischemia, and migrate to the site of injury along with blood vessels. However, a large fraction of stroke-generated neuroblasts die shortly after being born, in part, because of local inflammation. In spontaneously hypertensive rats (SHRs) subjected to permanent middle cerebral artery occlusion, we primed E-selectin-specific regulatory T cells (Tregs) by repetitive intranasal administration of recombinant E-selectin to target local secretion of immunomodulating, antiinflammatory cytokines to activating blood vessel segments. E-selectin-tolerized SHRs had decreased infarction volumes, and increased numbers of Tregs in the cervical lymph nodes and ischemic brain. The brain Tregs were distributed primarily in periinfarct regions. E-selectin tolerization did not alter cellular proliferation in the ipsilateral SVZ after stroke, but the expression of tumor necrosis factor on vascular niche blood vessels was suppressed and both doublecortin protein levels and the number of newly generated neuroblasts or neurons were increased in the brain. This enhanced survival of neural progenitor cells and neurons was paralleled by improved functional performance. These studies suggest that E-selectin-specific Tregs can modulate the efficacy of neurogenesis after ischemia and promote repair after brain injury.

Protective effect of post-ischaemic viral delivery of heat shock proteins in vivo

Heat shock proteins (HSPs) function as molecular chaperones involved in protein folding, transport and degradation and, in addition, they can promote cell survival both in vitro and in vivo after a range of stresses. Although some in vivo studies have suggested that HSP27 and HSP70 can be neuroprotective, current evidence is limited, particularly when HSPs have been delivered after an insult. The effect of overexpressing HSPs after transient occlusion of the middle cerebral artery in rats was investigated by delivering an attenuated herpes simplex viral vector (HSV-1) engineered to express HSP27 or HSP70 30 mins after tissue reperfusion. Magnetic resonance imaging scans were used to determine lesion size and cerebral blood flow at six different time points up to 1 month after stroke. Animals underwent two sensorimotor tests at the same time points to assess the relationship between lesion size and function. Results indicate that post-ischaemic viral delivery of HSP27, but not of HSP70, caused a statistically significant reduction in lesion size and induced a significant behavioural improvement compared with controls. This is the first evidence of effective post-ischaemic gene therapy with a viral vector expressing HSP27 in an experimental model of stroke.

Behavioral outcome measures for the assessment of sensorimotor function in animal models of movement disorders

Animal models have and continue to contribute to our understanding of the neurobiology many types of disorders. In movement disorders such as Parkinson's disease (PD), animal models have directly led to various therapeutic treatments such as deep brain stimulation. To facilitate the development of potential therapeutics, sensitive and reliable outcome measures in animal models are necessary to maximize their benefit. In this chapter, behavioral outcome measures, sensitive to varying degrees of sensorimotor dysfunction, are reviewed in rats and mice.

Neurological outcome and inflammation after cardiac arrest--effects of protein C in rats

BACKGROUND

The response of the human body to cardiac arrest (CA) and cardiopulmonary resuscitation is characterised by excessive coagulation, inadequate endogenous anti-coagulation and fibrinolysis as well as an inflammatory syndrome that closely resembles the immunological profile observed in patients with sepsis. Recombinant human activated protein C (rhAPC) has been found to be protective in severe sepsis and in animal models of stroke and spinal cord injury. In the present study, we evaluated the effects of rhAPC on neurological outcome after CA in rats.

METHODS

After 6 min of CA and subsequent cardiopulmonary resuscitation, male Wistar rats were randomized into 3 treatment groups: high dose rhAPC (2 mg/kg bolus and 0.1 mg/(kg h) for 6 h), low dose rhAPC (0.5 mg/kg and 0.025 mg/(kg h) for 6 h), and placebo (n=12 per treatment and reperfusion time). Neurological outcome was determined using a tape removal test and a composite neurological deficit score (NDS). As secondary measurements, we evaluated overall and neuronal survival, hippocampal caspase activity and inflammatory markers.

RESULTS

No difference between groups was found with the NDS. The tape removal test showed only a transitory improvement in the low dose group at 3 d after CA (P=0.041). No significant differences were observed for secondary measurements.

CONCLUSION

A clear and lasting effect of rhAPC on neurological outcome or inflammation after CA could not be shown in this study but the detailed analysis of the postresuscitation syndrome given here builds a firm basis for further research.

Enhanced function in the good forelimb of hemi-parkinson rats: compensatory adaptation for contralateral postural instability?

In this paper we present two new assays of rat motor behavior which can be used to assess function linked to postural stability in each forelimb independently. Postural instability is a major deficit in Parkinson's disease that is resistant to levodopa therapy and contributes to the risk of falling. We applied both tests, one forelimb at a time, to normal rats as well as rats extensively depleted of dopamine by unilateral infusion of 6-hydroxydopamine (6-OHDA, given in the medial forebrain bundle) to produce a hemi-parkinsonian syndrome. The 6-OHDA rats showed severe postural instability in the impaired forelimb, but unexpectedly showed enhanced function in the non-impaired forelimb. The data suggest that the intact hemisphere may undergo rapid reorganization subsequent to unilateral dopamine depletion, which allows for compensatory function of the "intact" limb. Measurements of amphetamine-induced striatal c-fos expression, as well as behavior results gathered when animals were under the influence of apomorphine or haloperidol, indicate that this potential reorganization may require non-dopaminergic neural plasticity. The relevance of these findings for unilateral rat models of neurological disease is discussed.

Levodopa improves skilled hand functions in the elderly

The endogenous dopamine system is a potent modulator of motor function and learning. Previous studies have demonstrated that, in the elderly, age-related degeneration of the nigrostriatal dopamine system may contribute to deficits in execution of skilled motor functions. The present double-blind, randomized cross-over study examined whether pharmacologically replenishing dopamine improves the execution of complex motor tasks. Twenty healthy young and 20 healthy elderly subjects were studied in two different sessions: (i) after three doses of levodopa (each 100 mg levodopa plus 25 mg carbidopa) and (ii) after three doses of placebo. For each session, subjects completed a functional motor test that reflects hand activities of daily living (Jebsen-Taylor test). In the elderly, but not in the young, Jebsen-Taylor test performance improved significantly (4%) with levodopa compared with placebo, particularly for fine motor functions. Attention to the task, level of fatigue, and positive and negative feelings were similar between sessions. These results demonstrate that increasing the dopaminergic drive pharmacologically may be helpful when the motor system is challenged in the ageing process.

Neurologic assessment of somatosensory dysfunction following an experimental rodent model of cerebral ischemia

The modified adhesive removal (sticky-tape) test is an assessment of somatosensory dysfunction following cerebral ischemia in rats. This test is less time consuming than the original protocol by virtue of requiring minimal pre-training. We present a detailed protocol describing how to conduct the modified adhesive removal (sticky-tape) test. Following right middle cerebral artery occlusion (rMCAo) using an intraluminal filament, animals undergo the modified sticky-tape test (MST) on post-operative days 1, 3, 7 and 10. For the test, a non-removable tape sleeve is placed around the animal's paw and the time to remove the stimulus is measured. The time spent attending to this stimulus is also recorded. Animals undergoing MST for the first time demonstrate nearly-uniform excellent performance. However, following rMCAo, the ratio of left to right performance on the MST is significantly different at all time points. In short, the MST accurately assesses neurological dysfunction in rodents, not only with minimal pre-training, but also with accurate localization to the side of injury.

Evaluation of a tape removal test to assess neurological deficit after cardiac arrest in rats

BACKGROUND

In animal models of cardiocirculatory arrest (CA) it is of major interest to establish tests that can assess neurological damage after global cerebral ischaemia following CA. We evaluated a tape removal test with regard to detection of sensorimotor deficit, comparing it to the Neurological Deficit Score (NDS) in an established model of global cerebral ischaemia after CA in rats.

METHODS

Rats were subjected to either 6 min of CA followed by cardiopulmonary resuscitation (CPR) or a sham operation. At 1, 3 and 7 days from the intervention, two different neurological tests were applied to all animals: in the tape removal test, the time was measured from attachment of adhesive tapes to the front paws until the animals removed them using their teeth and compared to latencies in the sham group. The NDS assessed two parameters ("travel beam" and "stop at the edge of a table"). Receiver operating characteristic (ROC) analysis was used to compare tests.

RESULTS

In the tape removal test, all animals of the CPR group showed a clear neurological deficit throughout the observation period with a marked recovery until day 7 (pre-CA: 4s, 1 day: 180 s, 3 days: 165 s, 7 days: 44 s; data are median values). Latencies differed significantly from those of sham-operated animals (1 day: P<0.001, 3 days: P=0.003, 7 days: P=0.006). ROC analysis showed that the tape removal test but not the NDS was appropriate for detecting neurological damage 3 and 7 days after restoration of spontaneous circulation (ROSC). Histological examination confirmed neuronal damage to the hippocampus, cortex, thalamus and striatum.

CONCLUSION

In the present study, a clinically relevant sensorimotor deficit after global cerebral ischaemia following cardiac arrest in rats has been quantified for the first time by using a tape removal test. The tape removal test is a sensitive method that can be easily applied to test large numbers of animals in future studies.

Gestational and lactational iron deficiency alters the developing striatal metabolome and associated behaviors in young rats

Gestational and early postnatal iron deficiency occurs commonly in humans and results in altered behaviors suggestive of striatal dysfunction. We hypothesized that early iron deficiency alters the metabolome of the developing striatum and accounts for abnormalities in striatum-dependent behavior in rats. Sixteen metabolite concentrations from a 9-11 microL volume within the striatum were serially assessed in 10 iron-deficient and 10 iron-sufficient rats on postnatal days 8, 22 (peak anemia), and 37 (following recovery from anemia) using (1)H NMR spectroscopy at 9.4 tesla. Chin-elicited bilateral forelimb placing and vibrissae-elicited unilateral forelimb placing were also assessed on these days. Iron deficiency altered metabolites indexing energy metabolism, neurotransmission, glial integrity, and myelination over time (P < 0.05). Successful development of behaviors was delayed in the iron-deficient group (P < or = 0.01). Alterations in creatine, glucose, glutamine, glutamate, N-acetylaspartate, myo-inositol, and glycerophosphorylcholine + phosphorylcholine concentrations accounted for 77-83% of the behavioral variability during peak anemia on postnatal day 22 in the iron-deficient group. Correction of anemia normalized the striatal metabolome but not the behaviors on postnatal day 37. These novel data imply that alterations in the metabolite profile of the striatum likely influence later neural functioning in early iron deficiency.

Striatal dopamine transporters correlate with simple reaction time in elderly subjects

The decline in motor performance that accompanies advanced age has unclear neurobiological substrates but may relate, in part, to degeneration of the nigrostriatal dopamine system. This research tested the hypothesis that striatal dopamine transporter (DAT) availability in healthy elderly individuals was related to measures of motor performance. Thirty-six healthy volunteers (18 male, 18 female) who ranged in age from 68 to 88 (75.4+/-4.9 years) received a neuropsychological evaluation that included two primary motor measures (tested with dominant hand): (1) simple reaction time (SRT); and (2) finger tapping (FT). Subjects underwent SPECT scanning with [(123)I]2beta-carbomethoxy-3beta-(4-iodophenyl)tropane ([(123)I]beta-CIT) for measurement of striatal DAT availability. A ratio of specific to nondisplaceable brain uptake (i.e., radical V3 =[striatal-occipital]/occipital), a measure proportional to the binding potential (B(max)/K(D)), was derived. SRT was significantly correlated with striatal DAT availability with or without controlling for the contribution of age. However, contrary to hypothesis, FT was not correlated with striatal DAT availability. Comparison measures, including episodic memory and general intelligence, were also unrelated to striatal DAT availability. These results demonstrate that a loss of nigrostriatal dopaminergic function likely contributes to slowing of reaction speed with advancing age.

Tissue sparing and functional recovery following experimental traumatic brain injury is provided by treatment with an anti-myelin-associated glycoprotein antibody

Axonal injury is a hallmark of traumatic brain injury (TBI) and is associated with a poor clinical outcome. Following central nervous system injury, axons regenerate poorly, in part due to the presence of molecules associated with myelin that inhibit axonal outgrowth, including myelin-associated glycoprotein (MAG). The involvement of MAG in neurobehavioral deficits and tissue loss following experimental TBI remains unexplored and was evaluated in the current study using an MAG-specific monoclonal antibody (mAb). Anesthetized rats (n=102) were subjected to either lateral fluid percussion brain injury (n=59) or sham injury (n=43). In surviving animals, beginning at 1 h post-injury, 8.64 microg anti-MAG mAb (n=33 injured, n=21 sham) or control IgG (n=26 injured, n=22 sham) was infused intracerebroventricularly for 72 h. One group of these rats (n=14 sham, n=11 injured) was killed at 72 h post-injury for verification of drug diffusion and MAG immunohistochemistry. All other animals were evaluated up to 8 weeks post-injury using tests for neurologic motor, sensory and cognitive function. Hemispheric tissue loss was also evaluated at 8 weeks post-injury. At 72 h post-injury, increased immunoreactivity for MAG was seen in the ipsilateral cortex, thalamus and hippocampus of brain-injured animals, and anti-MAG mAb was detectable in the hippocampus, fimbria and ventricles. Brain-injured animals receiving anti-MAG mAb showed significantly improved recovery of sensorimotor function at 6 and 8 weeks (P<0.01) post-injury when compared with brain-injured IgG-treated animals. Additionally, at 8 weeks post-injury, the anti-MAG mAb-treated brain-injured animals demonstrated significantly improved cognitive function and reduced hemispheric tissue loss (P<0.05) when compared with their brain-injured controls. These results indicate that MAG may contribute to the pathophysiology of experimental TBI and treatment strategies that target MAG may be suitable for further evaluation.

Behavioral models of Parkinson's disease in rodents: a new look at an old problem

The circuitry important for voluntary movement is influenced by dopamine from the substantia nigra and regulated by the nigrostriatal system. The basal ganglia influence the pyramidal tract and other motor systems, such as the mesopontine nuclei and the rubrospinal tract. Although the neuroanatomical substrates underlying motor control are similar for humans and rodents, the behavioral repertoire mediated by those circuits is not. The principal aim of this review is to evaluate how injury to dopamine-mediated pathways in rodents gives rise to motor dysfunction that mimics human Parkinsonism. We will examine the behavioral tests in common use with rodent models of Parkinson's disease and critically evaluate the appropriateness of each test for detecting motor impairment. We will show how tests of motor performance must be guided by a thorough understanding of the clinical symptoms accompanying the disease, the circuitry mediating dopamine deficits in rodents, and familiarity with the rodent behavioral repertoire. We will explain how investigations in rodents of skilled forepaw actions, including placing, grooming, or foot faults, have clear correlates in Parkinson's disease, and are, therefore, the most sensitive ways of detecting motor impairment following dopamine loss from the basal ganglia of rodents.

Behavioral phenotypes and pharmacology in genetic mouse models of Parkinsonism

Prior to the discovery of genes associated with familial forms of Parkinson's disease, animal models of Parkinson's disease mainly consisted of toxin models based exclusively on the degeneration of nigrostriatal dopamine neurons. These traditional models have provided valuable insight into symptomatic treatments for Parkinson's disease; however, they lack the broad extra-nigral pathology and the progression that is observed in the disease. The novel genetic mouse models recently generated are advantageous because they have mutations that are known to cause familial Parkinson's disease and thus they have good construct validity. To maximize the utility of these models, a thoughtful phenotypical characterization is important. Our laboratory has assembled a battery of behavioral tests to assess sensorimotor function in genetic mouse models of Parkinsonism. This review discusses the sensitivity of these tests in different genetic mice in addition to their behavioral response to dopamine agonists.

Early disruptions of the blood-brain barrier may contribute to exacerbated neuronal damage and prolonged functional recovery following stroke in aged rats

We examined the effects of age on stroke progression and outcome in order to explore the association between blood-brain barrier (BBB) disruption, neuronal damage, and functional recovery. Using middle cerebral artery occlusion (MCAO), young (3 months) and aged (18 months) rats were assessed for BBB disruption at 20min post-MCAO, and 24h post-MCAO with tissue plasminogen activator induced reperfusion at 120min. Results showed that BBB disruptions in aged rats occurred early and increased nearly two-fold at both the 20min and 24h time points when compared to young animals. Neuronal damage in aged rats was increased two-fold as compared to young rats at 24h, while no neuronal damage was observed at 20min. Young and aged rats exhibited neurological deficits when compared to sham-controls out to 14 days following MCAO and reperfusion; however, aged rats exhibited more severe onset of deficits and prolonged recovery. Results indicate that aged rats suffer larger infarctions, reduced functional recovery and increased BBB disruption preceding observable neuronal injury.

Behavioral tests for preclinical intervention assessment

Select functional outcome tests commonly used for evaluating sensorimotor and cognitive capacity in rodents with focal intracerebral ischemic or hemorrhagic injury are described, along with upgrades and issues of concern for translational research. An emphasis is placed on careful quantitative and qualitative assessment of acute and long-term behavioral deficits, and on avoidance of frequent pitfalls. Methods for detecting different degrees of injury and treatment-related improvements are included. Determining the true potential of an intervention requires a set of behavioral analyses that can monitor compensatory learning. In a number of preclinical outcome tests, animals can develop remarkably effective "tricks" that are difficult to detect but frequently lead to dramatic improvements in performance, particularly with repeated practice. However, some interventions may facilitate learning without promoting brain repair, but these may not translate into a meaningful level of benefit in the clinic. Additionally, it is important to determine whether there are any preinjury functional asymmetries in order to accurately assess damage-related changes in behavior. This is illustrated by the fact that some animals have chronic endogenous asymmetries and that others, albeit infrequently, can sustain a spontaneous cerebral stroke, without any experimental induction, that can lead to chronic deficits as reflected by behavioral, imaging, and histological analyses. Finally, a useful new modification of the water maze that involves moving the platform from trial to trial within the target quadrant is reviewed, and its advantages over the standard version are discussed.

Sensorimotor and cognitive deficits after transient middle cerebral artery occlusion in the mouse

Whereas behavioral impairments after stroke are increasingly studied in the rat, little is known about the long-term functional consequences of focal ischemia in the mouse. To address this issue, Swiss mice underwent transient (60 min) intraluminal occlusion of the middle cerebral artery (MCAo) or sham surgery. Sensorimotor (chimney, accelerating rotarod, pole, corner, adhesive removal and staircase tests) and cognitive (passive avoidance and Morris water maze) performances were regularly assessed during 1 month, after which the final histological lesion was measured. Motor coordination and balance, assessed by the chimney and rotarod tests, were transiently altered by MCAo. Moreover, bradykinesia was evidenced by the pole test. The most striking and long-lasting (1 month) sensorimotor deficits were postural asymmetries on the corner test, bilateral skilled forepaw reaching deficits on the staircase test and a contralateral sensorimotor impairment on the adhesive removal test. MCAo animals showed normal spatial learning abilities on the Morris water maze test, but they displayed learning deficits measured by the passive avoidance test. This latter deficit was significantly correlated with both cortical and striatal damage. Our findings demonstrate the usefulness of three tests that had never been reported in the mouse after ischemia: the adhesive removal, staircase and pole tests, which showed deficits 1 month after ischemia and should therefore constitute meaningful tools in mice for assessing both neuroprotective and regenerative therapies in stroke preclinical studies.

Persistent neurochemical and behavioral abnormalities in adulthood despite early iron supplementation for perinatal iron deficiency anemia in rats

BACKGROUND

Iron deficiency anemia (IDA) has been associated with altered cognitive, motor, and social-emotional outcomes in human infants. We recently reported that rats with chronic perinatal IDA, had altered regional brain iron, monoamines, and sensorimotor skill emergence during early development.

OBJECTIVE

To examine the long-term consequences of chronic perinatal IDA on behavior, brain iron and monoamine systems after dietary iron treatment in rats.

METHODS

Sixty dams were randomly assigned to iron-sufficient (CN) or low-iron (EID) diets during gestation and lactation. Thereafter, all offspring were fed the iron-sufficient diet, assessed for hematology and behavior after weaning and into adulthood and for brain measures as adults (regional brain iron, monoamines, dopamine and serotonin transporters, and dopamine receptor). Behavioral assessments included sensorimotor function, general activity, response to novelty, spatial alternation, and spatial water maze performance.

RESULTS

Hematology and growth were similar for EID and CN rats by postnatal day 35. In adulthood, EID thalamic iron content was lower. Monoamines, dopamine transporter, and dopamine receptor concentrations did not differ from CN. EID serotonin transporter concentration was reduced in striatum and related regions. EID rats had persisting sensorimotor deficits (delayed vibrissae-evoked forelimb placing, longer sticker removal time, and more imperfect grooming chains), were more hesitant in novel settings, and had poorer spatial water maze performance than CN. General activity and spatial alternation were similar for EID and CN.

CONCLUSION

Rats that had chronic perinatal IDA showed behavioral impairments that suggest persistent striatal dopamine and hippocampal dysfunction despite normalization of hematology, growth and most brain measures.

Mass-related traumatic tissue displacement and behavior: a screen for treatments that reduce [corrected] harm to bystander cells and recovery of function

In this study, we focused on a preclinical model of brain compression injury that has relevance to pathological conditions such as tumor, hematoma, blood clot, and intracerebral bony fragment. We investigated behavioral impairment as a result of rapid-onset small mass, and the factors involved in lesion formation and neuroplasticity. An epidural bead implantation method was adopted. Two sizes (1.5 mm and 2.0 mm thick) of hemisphere-shaped beads were used. The beads were implanted into various locations over the sensorimotor cortex (SMC--anterior, middle and posterior). The effects of early versus delayed bead removal were examined to model clinical neurosurgical or other treatment procedures. Forelimb and hind-limb behavioral deficits and recovery were observed, and histological changes were quantified to determine brain reaction to focal compression. Our results showed that the behavioral deficits of compression were influenced by the location, timing of compression release, and magnitude of compression. Even persistent compression by the thicker bead (2.0 mm) caused only minor behavioral deficits, followed by fast recovery within a week in most animals, suggesting a mild lesion pattern for this model. Brain tissue was compressed into a deformed shape under pressure with slight tissue damage, evidenced by pathological evaluation on hematoxylin and eosin (H&E)- and TUNEL-stained sections. Detectable but not severe behavioral dysfunction exhibited by this model makes it particularly suitable for direct assessment of adverse effects of interventions on neuroplasticity after brain compression injury. This model may permit development of treatment strategies to alleviate brain mass effects, without disrupting neuroplasticity.

Gauging recovery after hemorrhagic stroke in rats: implications for cytoprotection studies

Successful clinical translation of prospective cytoprotectants will likely occur only with treatments that improve functional recovery in preclinical (rodent) studies. Despite this assumption, many rely solely on histopathologic end points or the use of one or two simple behavioral tests. Presently, we used a battery of tests to gauge recovery after a unilateral intracerebral hemorrhagic stroke (ICH) targeting the striatum. In total, 60 rats (N=15 per group) were stereotaxically infused with 0 (SHAM), 0.06 (MILD lesion), 0.12 (MODERATE lesion), or 0.18 U (SEVERE lesion) of bacterial collagenase. This created a range of injury akin to moderate (from SEVERE to MODERATE or MODERATE to MILD lesion size approximately 30% reduction) and substantial cytoprotection (SEVERE to MILD lesion size--51% reduction). Post-ICH functional testing occurred over 30 days. Tests included the horizontal ladder and elevated beam tests, swimming, limb-use asymmetry (cylinder) test, a Neurologic Deficit Scale, an adhesive tape removal test of sensory neglect, and the staircase and single pellet tests of skilled reaching. Most tests detected significant impairments (versus SHAM), but only a few (e.g., staircase) frequently distinguished among ICH groups and none consistently differentiated among all ICH groups. However, by using a battery of tests we could behaviorally distinguish groups. Thus, preclinical testing would benefit from using a battery of behavioral tests as anything less may miss treatment effects. Such testing must be based on factors including the type of lesion, the postoperative delay and the time required to complete testing.

Delayed transplantation of human neurons following brain injury in rats: a long-term graft survival and behavior study

The NTera2 (NT2) cell line is a homogeneous population of cells, which, when treated in vitro with retinoic acid, terminally differentiate into postmitotic neuronal NT2N cells. Although NT2N neurons transplanted in the acute (24 h postinjury) period survive for up to 1 month following experimental traumatic brain injury (TBI), nothing is known of their ability to survive for longer periods or of their effects when engrafted during the chronic postinjury period. Adult male Sprague-Dawley rats (n = 348; 360-400 g) were initially anesthetized and subjected to severe lateral fluid-percussion (FP) brain injury or sham injury. At 1 month postinjury, only brain-injured animals showing severe neurobehavioral deficits received cryopreserved NT2N neurons stereotaxically transplanted into three sites in the peri-injured cortex (n = 18). Separate groups of similarly brain-injured rats received human fibroblast cells (n = 13) or cell suspension vehicle (n = 14). Sham-injured animals (no brain injury) served as controls and received NT2N transplants (n = 24). All animals received daily immunosuppression for three months. Behavioral testing was performed at 1, 4, 8, and 12 weeks post-transplantation, after which animals were sacrificed for histological analysis. Nissl staining and anti-human neuronal specific enolase (NSE) immunostaining revealed that NT2N neurons transplanted in the chronic post-injury period survived up to 12 weeks post-transplantation, extended processes into the host cortex and immunolabeled positively for synaptophysin. There were no statistical differences in cognitive or motor function among the transplanted brain-injured groups. Long-term graft survival suggests that NT2N neurons may be a viable source of neural cells for transplantation after TBI and also that these grafts can survive for a prolonged time and extend processes into the host cortex when transplanted in the chronic post-injury period following TBI.

An improved test of neurological dysfunction following transient focal cerebral ischemia in rats

The Adhesive Removal (sticky-tape) test is a commonly used test of somatosensory dysfunction following cerebral ischemia in rats. This test requires several days of pre-training prior to surgery, which can be time consuming. We present our results with an improved version of the sticky-tape test. Male Wistar rats were subjected to either sham surgery (n = 4) or right middle cerebral artery occlusion (rMCAo) using an intraluminal filament (n = 9), followed by a 10-day survival period. On post-operative days (POD) 1, 3, 7, and 10 animals underwent both the conventional sticky-tape test (CST) with measurement of the time to remove the stimulus (trs), as well as a modified sticky-tape test (MST), in which a non-removable tape sleeve was placed around the animal's paw. Time spent attending to this stimulus (tas) was recorded. Despite 3 days of pre-training, animals undergoing baseline CST still exhibited marked variability in pre-operative baseline test performance (trs range 1-60s). In contrast, animals undergoing MST for the first time demonstrated nearly uniformly excellent performance (% tas range 91.5-98.5% of the 30s testing period). Although, affected (left) limb performance on both CST (6.8-fold increase in trs on POD 1 compared to baseline) and MST (100% decrease in tas on POD 1 compared to baseline) was markedly altered by rMCAo, CST performance declined bilaterally, and no significant differences in the ratio of affected (left) and unaffected (right) limb performance between sham-operated and rMCAo animals were observed at any time point. In contrast, the ratio of left to right performance on the MST was significantly different at all time points (P<0.01). In conclusion, we present a simple modification of the widely used Adhesive Removal test and provide evidence that this test can accurately assess neurological dysfunction in rodents, not only with minimal pre-training, but also with improved localization of the side of injury.

Transplantation of hNT neurons into the ischemic cortex: Cell survival and effect on sensorimotor behavior

Cell transplantation offers a potential new treatment for stroke. Animal studies using models that produce ischemic damage in both the striatum and the frontal cortex have shown beneficial effects when hNT cells (postmitotic immature neurons) were transplanted into the ischemic striatum. In this study, we investigated the effect of hNT cells in a model of stroke in which the striatum remains intact and damage is restricted to the cortex. hNT cells were transplanted into the ischemic cortex 1 week after stroke induced by distal middle cerebral artery occlusion (dMCAo). The cells exhibited robust survival at 4 weeks posttransplant even at the lesion border. hNT cells did not migrate, but they did extend long neurites into the surrounding parenchyma mainly through the white matter. Neurite extension was predominantly toward the lesion in ischemic animals but was bidirectional in uninjured animals. Extension of neurites through the cortex toward the lesion was also seen when there was some surviving cortical tissue between the graft and the infarct. Prolonged deficits were obtained in four tests of sensory-motor function. hNT-transplanted animals showed a significant improvement in functional recovery on one motor test, but there was no effect on the other three tests relative to control animals. Thus, despite clear evidence of graft survival and neurite extension, the functional benefit of hNT cells after ischemia is not guaranteed. Functional benefit could depend on other variables, such as infarct location, whether the cells mature, the behavioral tests employed, rehabilitation training, or as yet unidentified factors.

Delayed inhibition of Nogo-A does not alter injury-induced axonal sprouting but enhances recovery of cognitive function following experimental traumatic brain injury in rats

Traumatic brain injury causes long-term neurological motor and cognitive deficits, often with limited recovery. The inability of CNS axons to regenerate following traumatic brain injury may be due, in part, to inhibitory molecules associated with myelin. One of these myelin-associated proteins, Nogo-A, inhibits neurite outgrowth in vitro, and inhibition of Nogo-A in vivo enhances axonal outgrowth and sprouting and improves outcome following experimental CNS insults. However, the involvement of Nogo-A in the neurobehavioral deficits observed in experimental traumatic brain injury remains unknown and was evaluated in the present study using the 11C7 monoclonal antibody against Nogo-A. Anesthetized, male Sprague-Dawley rats were subjected to either lateral fluid percussion brain injury of moderate severity (2.5-2.6 atm) or sham injury. Beginning 24 h post-injury, monoclonal antibody 11C7 (n=17 injured, n=6 shams included) or control Ab (IgG) (n=16 injured, n=5 shams included) was infused at a rate of 5 microl/h over 14 days into the ipsilateral ventricle using osmotic minipumps connected to an implanted cannula. Rats were assessed up to 4 weeks post-injury using tests for neurological motor function (composite neuroscore, and sensorimotor test of adhesive paper removal) and, at 4 weeks, cognition was assessed using the Morris water maze. Hippocampal CA3 pyramidal neuron damage and corticospinal tract sprouting, using an anterograde tracer (biotinylated dextran amine), were also evaluated. Brain injury significantly increased sprouting from the uninjured corticospinal tract but treatment with monoclonal antibody 11C7 did not further increase the extent of sprouting nor did it alter the extent of CA3 cell damage. Animals treated with 11C7 showed no improvement in neurologic motor deficits but did show significantly improved cognitive function at 4 weeks post-injury when compared with brain-injured, IgG-treated animals. To our knowledge, the present findings are the first to suggest that (1) traumatic brain injury induces axonal sprouting in the corticospinal tract and this sprouting may be independent of myelin-associated inhibitory factors and (2) that post-traumatic inhibition of Nogo-A may promote cognitive recovery unrelated to sprouting in the corticospinal tract or neuroprotective effects on hippocampal cell loss following experimental traumatic brain injury.

Lateral fluid percussion brain injury: a 15-year review and evaluation

This article comprehensively reviews the lateral fluid percussion (LFP) model of traumatic brain injury (TBI) in small animal species with particular emphasis on its validity, clinical relevance and reliability. The LFP model, initially described in 1989, has become the most extensively utilized animal model of TBI (to date, 232 PubMed citations), producing both focal and diffuse (mixed) brain injury. Despite subtle variations in injury parameters between laboratories, universal findings are evident across studies, including histological, physiological, metabolic, and behavioral changes that serve to increase the reliability of the model. Moreover, demonstrable histological damage and severity-dependent behavioral deficits, which partially recover over time, validate LFP as a clinically-relevant model of human TBI. The LFP model, also has been used extensively to evaluate potential therapeutic interventions, including resuscitation, pharmacologic therapies, transplantation, and other neuroprotective and neuroregenerative strategies. Although a number of positive studies have identified promising therapies for moderate TBI, the predictive validity of the model may be compromised when findings are translated to severely injured patients. Recently, the clinical relevance of LFP has been enhanced by combining the injury with secondary insults, as well as broadening studies to incorporate issues of gender and age to better approximate the range of human TBI within study design. We conclude that the LFP brain injury model is an appropriate tool to study the cellular and mechanistic aspects of human TBI that cannot be addressed in the clinical setting, as well as for the development and characterization of novel therapeutic interventions. Continued translation of pre-clinical findings to human TBI will enhance the predictive validity of the LFP model, and allow novel neuroprotective and neuroregenerative treatment strategies developed in the laboratory to reach the appropriate TBI patients.

Early and progressive sensorimotor anomalies in mice overexpressing wild-type human alpha-synuclein

Accumulation of alpha-synuclein in brain is a hallmark of synucleinopathies, neurodegenerative diseases that include Parkinson's disease. Mice overexpressing alpha-synuclein under the Thy-1 promoter (ASO) show abnormal accumulation of alpha-synuclein in cortical and subcortical regions of the brain, including the substantia nigra. We examined the motor deficits in ASO mice with a battery of sensorimotor tests that are sensitive to alterations in the nigrostriatal dopaminergic system. Male wild-type and ASO mice were tested every 2 months for 8 months for motor performance and coordination on a challenging beam, inverted grid, and pole, sensorimotor deficits in an adhesive removal test, spontaneous activity in a cylinder, and gait. Fine motor skills were assessed by the ability to grasp cotton from a bin. ASO mice displayed significant impairments in motor performance and coordination and a reduction in spontaneous activity as early as 2 months of age. Motor performance and coordination impairments became progressively worse with age and sensorimotor deficits appeared at 6 months. Fine motor skills were altered at 4 months and worsened at 8 months. These data indicate that overexpression of alpha-synuclein induced an early and progressive behavioral phenotype that can be detected in multiple tests of sensorimotor function. These behavioral deficits provide a useful way to assess novel drug therapy in genetic models of synucleinopathies.

An intermittent, controlled-rate, slow progressive degeneration model of Parkinson's disease: antiparkinson effects of Sinemet and protective effects of methylphenidate

The causes of nigrostriatal neuron degeneration in Parkinson's disease (PD) are not known, but it has been suggested that exogenous or endogenous factors or neurotoxins may play a role. The degree of vulnerability to neurotoxins or other potential mediators of nigral dopamine cell death is thought to be important in understanding Parkinson's disease. In most animal models, the rate of terminal degeneration and corresponding functional impairment is too rapid to investigate effectively either cell vulnerability or the potential benefits of some neuroprotective treatments. In the present study, a new model of Parkinson's disease is described that might help in addressing the issue of nigral cell vulnerability and to evaluate interventions with clinical potential. 6-Hydroxydopamine (6-OHDA) was infused in escalating, intrastriatal doses over several weeks. Control animals received multiple infusions of vehicle at the same volume. Behavioral testing was carried out between each infusion, including forelimb-use and somatosensory function. A symptomatic threshold was established for each animal, indicating the amount of neurotoxin required to induce a stable deficit. Oral administration of L-DOPA (Sinemet) ameliorated limb-use asymmetries acutely. An immunocytochemical assay for tyrosine hydroxylase, a dopamine cell marker, revealed a partial loss of immunoreactive cells in the substantia nigra. Animals that were co-administered methylphenidate (MPH), a dopamine transport inhibitor, along with the 6-OHDA were spared from the behavioral and neurochemical effects of 6-OHDA, despite receiving more than twice as much neurotoxin as controls. These data suggest that establishing a symptomatic threshold preclinically may help researchers evaluate potential treatments and model individual and group resistance to nigrostriatal insults.

Unilateral ischemic sensorimotor cortical damage induces contralesional synaptogenesis and enhances skilled reaching with the ipsilateral forelimb in adult male rats

Unilateral damage to the forelimb representation area of the sensorimotor cortex (SMC) results in a compensatory reliance on the unimpaired (ipsilateral to the lesion) forelimb as well as reorganization of neuronal structure and connectivity in the contralateral motor cortex. Recently, male rats with unilateral electrolytic SMC lesions were found to have enhanced skilled reaching performance with the ipsilesional forelimb compared with sham-operated controls. The present study was performed to determine whether these behavioral findings are replicable using an ischemic lesion and whether there is a link between the enhanced learning and synaptogenesis in motor cortical layer V opposite the trained limb and lesion, as assessed using stereological methods for light and electron microscopy. Rats were given a sham operation or an endothelin-1 (ET-1) induced ischemic SMC lesion. They were then trained for 20 days on a skilled reaching task with the unimpaired limb or received control procedures. As with previous findings using electrolytic lesions, rats with unilateral ischemic SMC lesions performed significantly better using the unimpaired forelimb than did sham-operates. Lesions, but not training, significantly increased the total number of motor cortical layer V synapses per neuron as well as the number of perforated and multisynaptic bouton (MSB) synapses per neuron compared with shams. Thus, in addition to a net increase in synapses, the improved reaching ability was coupled with an increase in synapse subtypes that have previously been linked to enhanced synaptic efficacy. The failure to induce synaptogenesis in layer V with reach training alone is in contrast to previous findings and may be related to training intensity.

Unilateral ischemic sensorimotor cortical damage in female rats: forelimb behavioral effects and dendritic structural plasticity in the contralateral homotopic cortex

Previous studies in male rats with unilateral sensorimotor cortical (SMC) damage have demonstrated dendritic structural plasticity in the contralateral homotopic cortex and an enhancement of skilled reaching performance in the forelimb ipsilateral to the lesion compared to sham-operated rats. The purpose of this study was to determine if these findings could be replicated in an ischemic lesion model in female rats. Female rats were given sham operations or unilateral ischemic (endothelin-1 induced) damage in the forelimb representation area of the SMC opposite their preferred forelimb. Animals then received either 20 consecutive days of training on a skilled reaching task with the non-preferred/unimpaired forelimb or no-training control procedures. The surface density of dendrites immunoreactive (IR) for microtubule-associated protein 2 (MAP2) was then measured in the motor cortex opposite the trained limb and/or lesion. Female rats with sufficiently large, but not very small, lesions performed better with the unimpaired forelimb than sham-operated rats on the reaching task. The post-lesion reaching performance was not found to be significantly dependent upon estrous stage at the time of surgery, in agreement with previous studies that failed to find sex or sex-hormone effects after other types of SMC damage. Additionally, there were major laminar-dependent increases in the surface density of MAP2 IR dendrites in the cortex opposite lesions and trained limbs. These findings in female rats are consistent with the dendritic and behavioral changes previously found in male rats. They extend these previous findings by indicating that lesion size is an important variable in the enhancement of reaching performance.

Evidence for bilateral control of skilled movements: ipsilateral skilled forelimb reaching deficits and functional recovery in rats follow motor cortex and lateral frontal cortex lesions

Unilateral damage to cortical areas in the frontal cortex produces sensorimotor deficits on the side contralateral to the lesion. Although there are anecdotal reports of bilateral deficits after stroke in humans and in experimental animals, little is known of the effects of unilateral lesions on the same side of the body. The objective of the present study was to make a systematic examination of the motor skills of the ipsilateral forelimb after frontal cortex lesions to either the motor cortex by devascularization of the surface blood vessels (pial stroke), or to the lateral cortex by electrocoagulation of the distal branches of the middle cerebral artery (MCA stroke). Plastic processes in the intact hemisphere were documented using Golgi-Cox dendritic analysis and by intracortical microstimulation analysis. Although tests of reflexive responses in forelimb placing identified a contralateral motor impairment following both cortical lesions, quantitative and qualitative measures of skilled reaching identified a severe ipsilateral impairment from which recovery was substantial but incomplete. Golgi-impregnated pyramidal cells in the forelimb area showed an increase in dendritic length and branching. Electrophysiological mapping showed normal size forelimb representations in the lesioned rats relative to control animals. The finding of an enduring ipsilateral impairment in skilled movement is consistent with a large but more anecdotal literature in rats, nonhuman primates and humans, and suggests that plastic changes in the intact hemisphere are related to that hemisphere's contribution to skilled movement.

Human neural stem/progenitor cells, expanded in long-term neurosphere culture, promote functional recovery after focal ischemia in Mongolian gerbils

Transplantation of human neural stem cells (NSCs) is a promising potential therapy for neurologic dysfunctions after the hyperacute stage of stroke in humans, but large amounts of human NSCs must be expanded in long-term culture for such therapy. To determine their possible therapeutic potential for human stroke, human fetal neural stem/progenitor cells (NSPCs) (i.e., neurosphere-forming cells) were isolated originally from forebrain tissues of one human fetus, and expanded in long-term neurosphere culture (exceeding 24 weeks), then xenografted into the lesioned areas in the brains of Mongolian gerbils 4 days after focal ischemia. Sensorimotor and cognitive functions were evaluated during the 4 weeks after transplantation. The total infarction volume in the NSPC-grafted animals was significantly lower than that in controls. Approximately 8% of the grafted NSPCs survived, mainly in areas of selective neuronal death, and were costained with antibodies against neuronal nuclei antibody (NeuN), microtubule associated protein (MAP-2), glial fibrillary acidic protein (GFAP), and anti-2'3' cyclic nucleotide 3'-phosphodiesterase (CNPase). Synaptic structures between NSPCs-derived neurons and host neurons were observed. Furthermore, gradual improvement of neurologic functions was observed clearly in the NSPC-grafted animals, compared to that in controls. Human NSPCs, even from long-term culture, remarkably improved neurologic functions after focal ischemia in the Mongolian gerbil, and maintained their abilities to migrate around the infarction, differentiate into mature neurons, and form synapses with host neuronal circuits. These results indicate that in vitro-expanded human neurosphere cells are a potential source for transplantable material for treatment of stroke.

Motor and cognitive function evaluation following experimental traumatic brain injury

Traumatic brain injury (TBI) in humans may cause extensive sensorimotor and cognitive dysfunction. As a result, many TBI researchers are beginning to assess behavioral correlates of histologically determined damage in animal models. Although this is an important step in TBI research, there is a need for standardization between laboratories. The ability to reliably test treatments across laboratories and multiple injury models will close the gap between treatment success in the lab and success in the clinic. The goal of this review is to describe and evaluate the tests employed to assess functional outcome after TBI and to overview aspects of cognitive, sensory, and motor function that may be suitable targets for therapeutic intervention.

High-frequency stimulation of the subthalamic nucleus reverses limb-use asymmetry in rats with unilateral 6-hydroxydopamine lesions

Deep brain stimulation (DBS) is a widely used clinical treatment for Parkinson's disease (PD). A rodent model of DBS is a necessary tool for understanding the neural mechanisms of this method. Our previous study showed that high-frequency stimulation (HFS) of the subthalamic nucleus (STN) improved treadmill locomotion in rats with unilateral 6-hydroxydopamine (6-OHDA)-induced lesions of nigrostriatal dopamine (DA) neurons. The present study tested DBS effects on limb-use asymmetry (LUA) during vertical/lateral exploration in a cylindrical chamber in rats with similar unilateral nigrostriatal DA lesions. Limb-use asymmetry assessment has been used to detect functional capacity over a wide range of dopamine depletion. Before lesioning, rats exhibited regular rearing activity and used both forelimbs equally often to support weight during exploration of the walls of the cylinder. After unilateral nigrostriatal DA lesioning, rats displayed reduced rearing activity and predominant use of the ipsilateral (good) forelimb to touch the wall. HFS of the STN, but not of other nearby regions surrounding the STN, in the lesioned rats restored normal rearing activity and reversed the limb-use asymmetry caused by the unilateral DA depletion. This study is consistent with the possibility that there can be beneficial effects of STN-DBS on behavioral impairments in unilateral DA-depleted rats and may suggest an appropriate rodent model for DBS study.

Chronic behavioral testing after focal ischemia in the mouse: functional recovery and the effects of gender

Several useful behavioral tests exist for measuring behavioral recovery after ischemia in higher-order animals and rats. With the increasing use of mice in focal stroke research, simple, reliable, and reproducible behavioral testing has become a priority. As neuroprotective agents are tested, long-term outcome must be assessed, especially in studies focused on neuronal plasticity and regeneration after ischemia. Our laboratory and others have previously shown that estrogen (E2) is neuroprotective in rodent stroke paradigms. We examined a battery of behavioral tests in male and female mice subjected to 90 min of middle cerebral artery occlusion (MCAO) to determine the most sensitive tests for detecting sensorimotor dysfunction after stroke, and to determine the functional significance of E2-mediated neuroprotection. Only two tests, the corner test and the cylinder test, were able to differentiate between groups (sham and stroke) after several days of repeated testing. The cylinder test was sensitive to the neuroprotective/neurorestorative effects of E2, but 2 weeks after stroke, the cylinder test was unable to distinguish between sham and stroke animals treated with E2. In contrast, the corner test was able to differentiate stroke and sham animals even 6 weeks after stroke, but did not distinguish animals treated with E2 vs. vehicle. These tests provide a simple, rapid, reliable assessment of sensorimotor dysfunction in the mouse after focal ischemia. Hormonal status influences speed of recovery on cylinder testing in animals of both genders. This suggests that a short battery of tests including the neurological score, cylinder, and corner test may be adequate to rapidly and repeatedly assess sensorimotor dysfunction in mice of both genders.

The window of opportunity for treatment of focal cerebral ischemic damage with noninvasive intranasal insulin-like growth factor-I in rats

Intracerebroventricular injection of insulin-like growth factor (IGF)-I has been shown to protect against stroke in rats. This method of delivery is not practical in human beings, as it requires an operation with risk of infection and other complications. Intranasal (i.n.) delivery offers a noninvasive method of bypassing the blood-brain barrier to deliver IGF-I to the brain. This study delineates the window of opportunity for treatment of focal cerebral ischemic damage using i.n. IGF-I after middle cerebral artery occlusion (MCAO). Rats were allowed to survive 7 days after 2 hours of MCAO. Infarct volume, apoptosis after 7 days, and neurologic deficit scores from the postural reflex and adhesive tape tests assessing motor-sensory and somatosensory functions, respectively, at 1 to 7 days were used to evaluate the efficacy of i.n. IGF-I (150 microg) administered at different times after MCAO. I.n. IGF-I significantly reduced infarct volume by 54%; and 39%; versus control when administered at 2 or 4 hours, respectively, after the onset of MCAO (P < .05) and improved motor-sensory and somatosensory functions (P < .05) when administered 2 hours after the onset of MCAO. In addition, treatment with i.n. IGF-I at 2, 4, or 6 hours after MCAO decreased apoptotic cell counts by more than 90%; in the hemisphere ipsilateral to the occlusion. I.n. IGF-I is a promising treatment for stroke with a therapeutic window of opportunity for up to 6 hours after the onset of ischemia. This noninvasive method provides a simpler, safer, and potentially more cost-effective method of delivery than other methods currently in use.

A new primate model of focal stroke: endothelin-1-induced middle cerebral artery occlusion and reperfusion in the common marmoset

The purpose of the present set of studies was to develop a new primate model of focal ischemia with reperfusion for long-term functional assessment in the common marmoset. Initially, the cerebral vascular anatomy of the marmoset was interrogated by Araldite-cast and ink-perfusion methods to determine the feasibility of an intravascular surgical approach. The methods showed that the internal carotid artery was highly tortuous in its passage, precluding the development of an extracranial method of inducing temporary middle cerebral artery occlusion in the marmoset. A pilot dose-response study investigated an intracranial approach of topically applying endothelin-1 (ET-1) to the M2 portion of the middle cerebral artery in a small sample of marmosets for up to 6 hours (n = 2 or 3 per group). Dose-dependent reductions in middle cerebral artery vessel caliber followed by gradual reperfusion were inversely related to increases in corrected lesion volume after ET-1 treatment, relative to vehicle control application. Finally, the functional consequences of ET-1-induced lesions to the M2 vascular territory were assessed up to 24 hours after surgery using the optimal dose established in the pilot study (2.5 nmol/25 microL). ET-1-treated marmosets (n = 4) showed marked contralateral motor deficits in grip strength and retrieval of food rewards and contralateral sensory/motor neglect towards tactile stimulation, relative to their ipsilateral side and vehicle-treated marmosets (n = 4). Strong correlations were shown between contralateral impairments and histopathologic parameters, which revealed unilateral putamen and cortical damage to the middle cerebral artery territory. No deficits were shown on general mobility, and self-care was promptly resumed in ET-1 marmosets after surgery. These results show that this novel model of ischemia with reperfusion in the marmoset has the potential to assess long-term function and to gauge the efficacy of novel therapeutic strategies targeted for clinical stroke.

Long-lasting functional disabilities in middle-aged rats with small cerebral infarcts

Recommendations from experts and recently established guidelines on how to improve the face and predictive validity of animal models of stroke have stressed the importance of using older animals and long-term behavioral-functional endpoints rather than relying almost exclusively on acute measures of infarct volume in young animals. The objective of the present study was to determine whether we could produce occlusions in older rats with an acceptable mortality rate and then detect reliable, long-lasting functional deficits. A reversible intraluminar suture middle cerebral artery occlusion (MCAO) procedure was used to produce small infarcts in middle-aged rats. This resulted in an acceptable mortality rate, and robust disabilities were detected in functional assays, although the degree of total tissue loss measured 90 d after MCAO was quite modest. Infarcted animals were functionally impaired relative to sham control animals even 90 d after the occlusions, and when animals were subgrouped based on amount of tissue loss, MCAO animals with only 4% tissue loss exhibited enduring neurological-behavioral impairments relative to sham-operated controls, and the functional impairments in the group with the largest infarcts (20% tissue loss) were more severe than the functional impairments in the rats with 4% tissue loss. These results suggest that this model, using reversible MCAO to produce small infarcts and long-lasting functional-behavioral deficits in older rats, may represent an advance in the relatively higher-throughput modeling of stroke and its recovery in rodents and may be useful in the development and characterization of future stroke therapies.

Parkin-deficient mice exhibit nigrostriatal deficits but not loss of dopaminergic neurons

Loss-of-function mutations in parkin are the major cause of early-onset familial Parkinson's disease. To investigate the pathogenic mechanism by which loss of parkin function causes Parkinson's disease, we generated a mouse model bearing a germline disruption in parkin. Parkin-/- mice are viable and exhibit grossly normal brain morphology. Quantitative in vivo microdialysis revealed an increase in extracellular dopamine concentration in the striatum of parkin-/- mice. Intracellular recordings of medium-sized striatal spiny neurons showed that greater currents are required to induce synaptic responses, suggesting a reduction in synaptic excitability in the absence of parkin. Furthermore, parkin-/- mice exhibit deficits in behavioral paradigms sensitive to dysfunction of the nigrostriatal pathway. The number of dopaminergic neurons in the substantia nigra of parkin-/- mice, however, is normal up to the age of 24 months, in contrast to the substantial loss of nigral neurons characteristic of Parkinson's disease. Steady-state levels of CDCrel-1, synphilin-1, and alpha-synuclein, which were identified previously as substrates of the E3 ubiquitin ligase activity of parkin, are unaltered in parkin-/- brains. Together these findings provide the first evidence for a novel role of parkin in dopamine regulation and nigrostriatal function, and a non-essential role of parkin in the survival of nigral neurons in mice.

High frequency stimulation of the subthalamic nucleus has beneficial antiparkinsonian effects on motor functions in rats, but less efficiency in a choice reaction time task

Chronic subthalamic nucleus high frequency stimulation (STN HFS) improves motor function in Parkinson's disease. However, its efficacy on cognitive function and the mechanisms involved are less known. The aim of this study was to assess the effects of STN HFS in hemiparkinsonian awake rats performing different specific motor tests and a cognitive operant task. Unilateral STN HFS applied in unilaterally DA-depleted rats decreased the apomorphine-induced circling behaviour and reduced catalepsy induced by the neuroleptic haloperidol. DA-depleted rats exhibited severe deficits in the operant task, among which the inability to perform the task was not alleviated by STN HFS. However, in a few animals showing less impairment, STN HFS significantly reduced the contralateral neglect induced by the lesion. These results are the first to demonstrate a beneficial effect of STN HFS applied in awake rats on basic motor functions. However, STN HFS appears to be less effective on impaired cognitive functions.

Neurological dysfunctions versus regional infarction volume after focal ischemia in Mongolian gerbils

BACKGROUND AND PURPOSE

With advances in the therapy of stroke at the postacute phase, the use of animal models for chronological and region-specific evaluation of neurological function has become increasingly important. Our aim was to test long-term behavioral dysfunction in gerbils after focal ischemia and to correlate the results with the regional distribution of infarction in the coordinating cortical regions.

METHODS

Repetitive unilateral hemispheric ischemia (two 10-minute occlusions, 5-hour interval) was induced in Mongolian gerbils. The elevated body swing test (EBST), bilateral asymmetry test (BAT), and T-maze test were performed to assess asymmetrical motor behavior, somatosensory deficit, and spatial cognitive dysfunction during 4 weeks after ischemia. The results were correlated against the regional infarction volume of the primary motor, somatosensory, and primary visual cortices at 4 weeks after ischemia.

RESULTS

In all postischemic gerbils, persistent sensorimotor and cognitive dysfunctions were detectable throughout the postischemic period. Histological examination revealed that a cortical zone of infarction surrounded the selective neuronal death in the ipsilateral cerebral hemisphere. The regional infarction volumes of the primary motor, somatosensory, and visual cortices were significantly correlated with the scores of the EBST, BAT, and T-maze test, respectively. These combinations had the highest regression coefficient of all pairs.

CONCLUSIONS

Postischemic motor and somatosensory functions were significantly correlated with regional infarction volumes in the corresponding cortical regions. In gerbils, visual abnormality could be independently detected by the T-maze test. Such regional analyses of ischemic lesions would be useful for investigating the functional outcomes of stroke therapy.

Cholinergic and serotonergic neocortical projection lesions given singly or in combination cause only mild impairments on tests of skilled movement in rats: evaluation of a model of dementia

The cholinergic (ACh) projections of the nucleus basalis and the serotonergic (5-HT) projections of the raphe nuclei to the neocortex are required for the normal function of the neocortex. Nevertheless, damage to either system alone has little effect on the behavior of rats, but conjoint damage to both systems is reported to produce dementia to the point that animals are described as being unable to engage in intelligent behavior. Because rats with bilateral damage to both systems are so severely impaired, they are not useful for chronic studies. The objective of the present research was to determine whether unilateral depletions produce a functional impairment. Rats received unilateral neurotoxic lesions to either the nucleus basalis (quisqualic acid), or the medial forebrain bundle (5,7-dihydroxytryptamine), or both, which reduced neocortical levels of ACh (55%) and 5-HT (63%). The rats then received a battery of tests sensitive to unilateral neocortical injury. The 5-HT lesion produced no quantitative or qualitative deficits on reaching for food, walking across a horizontal ladder, forelimb placement in a cylinder, sensory detection of adhesive paper applied to the wrists, or forelimb inhibition during swimming. The ACh lesion produced mild qualitative deficits in reaching. Combined lesions produced mild deficits in skilled reaching, ladder walking, and sensory detection. In contrast to the mild impairments produced by the lesions, pharmacological blockade of either ACh with atropine or 5-HT with methiothepin mesylate systemically blocked skilled motor behavior as assessed by skilled reaching. The results are discussed in relation to the problems associated with the development of a unilateral model of dementia.