Analysis of locomotion is an important tool in the study of peripheral and central nervous system damage. Most locomotor scoring systems in rodents are based either upon open field locomotion assessment, for example, the BBB score or upon foot print analysis. The former yields a semiquantitative description of locomotion as a whole, whereas the latter generates quantitative data on several selected gait parameters. In this paper, we describe the use of a newly developed gait analysis method that allows easy quantitation of a large number of locomotion parameters during walkway crossing. We were able to extract data on interlimb coordination, swing duration, paw print areas (total over stance, and at 20-msec time resolution), stride length, and base of support: Similar data can not be gathered by any single previously described method. We compare changes in gait parameters induced by two different models of spinal cord injury in rats, transection of the dorsal half of the spinal cord and spinal cord contusion injury induced by the NYU or MASCIS device. Although we applied this method to rats with spinal cord injury, the usefulness of this method is not limited to rats or to the investigation of spinal cord injuries alone.

The mesencephalic dopamine (mesDA) system is involved in the control of movement and behavior. The expression of Pitx3 in the brain is restricted to the mesDA system and the gene is induced relatively late, at E11.5, a time when tyrosine hydroxylase (Th) gene expression is initiated. We show here that, in the Pitx3-deficient aphakia(ak) mouse mutant, the mesDA system is malformed. Owing to the developmental failure of mesDA neurons in the lateral field of the midbrain,mesDA neurons are not found in the SNc and the projections to the caudate putamen are selectively lost. However, Pitx3 is expressed in all mesDA neurons in control animals. Therefore, mesDA neurons react specifically to the loss of Pitx3. Defects of motor control where not seen in the ak mice,suggesting that other neuronal systems compensate for the absence of the nigrostriatal pathway. However, an overall lower activity was observed. The results suggest that Pitx3 is specifically required for the formation of the SNc subfield at the onset of dopaminergic neuron differentiation.

Gait analysis plays an important role in the assessment of neurological function in many disease models. In this review, we focus on the newly developed CatWalk system for gait analysis. CatWalk was originally developed as a tool to enhance assessment of functional outcome in spinal cord injury (SCI) models. Although it is also of value in models of among others (neuropathic) pain and peripheral nerve damage, we will limit ourselves to its use in SCI models in this review. The system is positioned against well-established locomotor function tests, and it is indicated how CatWalk can enhance the usefulness of such tests. Development of the system started with the idea that it should enable objective assessment of coordination, and powerful measures of coordination are nowadays included in the analysis options provided by CatWalk. Therefore, a major part of this review is devoted to the history and meaning of these coordination measures.

Spinal cord trauma leads to loss of motor, sensory and autonomic functions below the lesion. Recovery is very restricted, due in part to neurite growth inhibitory myelin proteins, in particular Nogo-A. Two neutralizing antibodies against Nogo-A were used to study recovery and axonal regeneration after spinal cord lesions. Three months old Lewis rats were tested in sensory-motor tasks (open field locomotion, crossing of ladder rungs and narrow beams, the CatWalk(R) runway, reactions to heat and von Frey hairs). A T-shaped lesion was made at T8, and an intrathecal catheter delivered highly purified anti-Nogo-A monoclonal IgGs or unspecific IgGs for 2 weeks. A better outcome in motor behavior was obtained as early as two weeks after lesion in the animals receiving the Nogo-A antibodies. Withdrawal responses to heat and mechanical stimuli were not different between the groups. Histology showed enhanced regeneration of corticospinal axons in the anti-Nogo-A antibody groups. fMRI revealed significant cortical responses to stimulation of the hindpaw exclusively in anti-Nogo-A animals. These results demonstrate that neutralization of the neurite growth inhibitor Nogo-A by intrathecal antibodies leads to enhanced regeneration and reorganization of the injured CNS, resulting in improved recovery of compromised functions in the absence of dysfunctions.

Most experimental studies of spinal cord injury (SCI) in rats damage the thoracic cord, with the consequent functional loss being due to interruption of long tracts connecting the caudal spinal cord to the rostral nervous system. Less work has been done evaluating injury to the cervical cord, even though it is the most common level of human SCI. In addition to the long tracts, the cervical spinal cord contains the sensory and motor neurons responsible for upper extremity function. The purpose of this study was to further develop a rat model of cervical spinal cord contusion injury using a modified NYU/MASCIS weight drop device. Mild (6.25 mm) and moderate (12.5 mm) C5 unilateral injuries were produced. Behavioral recovery was examined using a grooming test, a paw preference test, a walkway test (The Catwalk), and a horizontal ladder test. Histological outcome measures included sparing at the lesion epicenter, sparing throughout the extent of the lesion, quantification of myelin loss rostral and caudal to the lesion, and motor neuron counts. Compared to controls, animals receiving SCI exhibited injury severity-specific deficits in forelimb, locomotor, and hindlimb function persisting for 6-weeks post-SCI. Histological analysis revealed ipsilateral containment of the injury, and differentiation between groups on all measures except motor neuron counts. This model has many advantages: (1) minimal animal care requirements post-SCI, (2) within subject controls, (3) functional loss involves primarily the ipsilateral forelimb, and (4) it is a behavioral and histological model for both gray and white matter damage caused by contusive SCI.