Gait Impairment in a Rat Model of Focal Cerebral Ischemia

Hindawi Publishing Corporation Stroke Research and Treatment Volume 2013, Article ID 410972, 12 pages http://dx.doi.org/10.1155/2013/410972 Research Article Gait Impairment in a Rat Model of Focal Cerebral Ischemia Saara Parkkinen,1 Francisco J. Ortega,1 Kristina Kuptsova,1 Joanna Huttunen,2 Ina Tarkka,3 and Jukka Jolkkonen1 1 Department of Neurology, Institute of Clinical Medicine, University of Eastern Finland, Yliopistonranta 1 C, 70210 Kuopio, Finland A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, 70210 Kuopio, Finland 3 Department of Health Sciences, University of Jyväskylä, 40014 Jyväskylä, Finland 2 Correspondence should be addressed to Jukka Jolkkonen; Received 5 October 2012; Revised 17 December 2012; Accepted 27 December 2012 Academic Editor: Gerlinde Metz Copyright © 2013 Saara Parkkinen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The availability of proper tests for gait evaluation following cerebral ischemia in rats has been limited. The automated, quantitative CatWalk system, which was initially designed to measure gait in models of spinal cord injury, neuropathic pain, and peripheral nerve injury, is said to be a useful tool for the study of motor impairment in stroke animals. Here we report our experiences of using CatWalk XT with rats subjected to transient middle cerebral artery occlusion (MCAO), during their six-week followup. Large corticostriatal infarct was confirmed by MRI in all MCAO rats, which was associated with severe sensorimotor impairment. In contrast, the gait impairment was at most mild, which is consistent with seemingly normal locomotion of MCAO rats. Many of the gait parameters were affected by body weight, walking speed, and motivation despite the use of a goal box. In addition, MCAO rats showed bilateral compensation, which was developed to stabilize proper locomotion. All of these interferences may confound the data interpretation. Taken together, the translational applicability of CatWalk XT in evaluating motor impairment and treatment efficacy remains to be limited at least in rats with severe corticostriatal infarct and loss of body weight. 1. Introduction Stroke imposes an enormous economic and human burden. Despite some spontaneous recovery observed during the first 3 months, around half of stroke patients are left with permanent disability, in which upper extremity motor impairment is the most prominent. Most hemiplegic patients also have a gait abnormality including decreased velocity, cadence, stride length, and prolonged swing phase on the affected side [1]. In addition to reduced ambulation, this could impair balance and lead to falls [2]. Perhaps the most common experimental stroke model is transient middle cerebral artery occlusion (MCAO) [3], which reproduces many features of human stroke. Numerous tests are available to assess behavioral impairment in MCAO rats, varying from simple tasks measuring general severity of neurological impairment to more demanding reaching tasks that measure upper extremity function [3–5]. Versatile analysis of gait and ambulation has been limited in stroke animals until the CatWalk system was recently introduced as an automated and quantitative gait analysis tool. It is based on video analysis of light reflected by the paws as they contact the glass floor. This represents a rapid way to objectively quantify several gait parameters such as position, pressure and surface area of each paw, which are used to calculate spatial paw statistics, the relative positions between paws, temporal parameters of gait, and interlimb coordination. This system has clinical relevance because the principle is very similar to the GAITRite system that can assess gait in stroke patients [1]. Recently, four papers have described the use of CatWalk in experimental stroke models. Wang et al. [6] studied gait 4 days and 5 weeks after cortical lesion (pMCAO model). Four days after ischemia, the intensity and maximal area of the affected forepaw were significantly decreased. They also found impairment of interlimb coordination. Most of these impairments persisted for 5 weeks. Vandeputte et al. [7] showed reduced intensity, print area, and width max area of the contralateral hindlimbs one day after cortical photothrombosis (Rose Bengal model). Encarnacion et al. [8] tested two rat strains after transient MCAO (filament model). 2 They showed short-term deficits in intensity, stride length, stand index, duty cycle, and placement time of the impaired forelimb. In this study, deficits in hindlimb swing speed and placement time were more long lasting. Hetze et al. [9] showed decreases in maximum contact area, stride length, and swing speed in the impaired hindlimb following transient MCAO in mice. MCAO rats usually develop compensatory strategies to overcome motor deficits. This has not been evaluated in the aforementioned studies although there is data available for all limbs. Another issue that has not been discussed is the difficulty to motivate the rats to cross the runway in a consistent manner without stopping and turning around. To overcome this, a goal box can be mounted at the end of the runway in the CatWalk XT version 9.1. Here we report our experiences in using CatWalk XT with a goal box in rats subjected to transient MCAO. 2. Material and Methods 2.1. Animals. Male Wistar rats (BE Harlan Laboratories Ltd., Israel), 3 months old, weighing 350–400 g at the beginning of the study were used. The rats were housed individually under 12 h/12 h day and night cycles in a temperature-controlled environment (20±1∘ C). All animal procedures were approved by the Animal Ethics Committee (Hämeenlinna, Finland) and conducted in accordance with the guidelines set by the European Community Council Directives 86/609/EEC. All efforts were made to minimize the number of animals used and to ensure their welfare throughout. 2.2. Middle Cerebral Artery Occlusion. Focal cerebral ischemia was induced by the intraluminal filament technique (𝑛 = 7) [10]. Under halothane anesthesia, the right common carotid artery was exposed through a midline cervical incision. A heparinized nylon filament (diameter 0.25 mm, rounded tip) was inserted into the stump of the external common carotid artery. The filament was advanced 1.8–2.1 cm into the internal common carotid artery until resistance was felt. After 60 minutes of occlusion, the filament was removed and the external carotid artery was permanently closed by electrocoagulation. The sham-operated rats (𝑛 = 6) were treated in a similar manner, except that the filament was not placed into the internal carotid artery. The neurological impairment was assessed 24 hours after MCAO using a modified version of the limb-placing test [11] and animals with no behavioral impairment were (...truncated)