A new method to assess weight-bearing distribution after central nervous system lesions in rats

The aim of the present study is to assess the relevance of weight-bearing distribution (DWB) measurement in freely moving rats after stroke and thoracic spinal cord injuries. Animals were divided in 2 experiments: (1) The middle cerebral artery occlusion-reperfusion (MCAO-r) experiment containing the MCAO group in which focal brain ischaemia was induced by transient MCA occlusion and (2) the thoracic hemisection experiment containing the TH group in which a spinal cord hemisection was performed at the T10 level. A Control and respective Sham groups were also included in each experiment. Not only the pressure exerted by each paw was measured but also different ratios such as: (1) the sum of the right and the left forepaws was normalized by the sum of the right and the left hindpaws (F/H), (2) the left forepaw was normalized by the right forepaw (LF/RF), (3) the left hindpaw was normalized by the right hindpaw (LH/RH). Additionally, the times spent on 3 paws and on 4 paws were measured. Only the time spent on 4 paws was shorter in the MCAO group than in the Control (p<0.001) and in the Sham (p<0.01) groups. The LH/RH ratio of the TH group at the 1st week was lower (p<0.01) than the pre-surgical value. Moreover, its F/H ratio was superior (p<0.001) to the ones of the Control and the Sham groups. Our study indicates that DWB should be more frequently used to evaluate both the severity of central nervous system traumas and the effectiveness of pharmacological and/or rehabilitation strategies.