Influence of sequential photothrombotic cortical lesions on forelimb use in rats
S. Reinecke1, E. Shanina1, T. Schallert2 and O.W. Witte1
1Neurological Hospital, Clinic Centre of FSU, Jena, Germany
2University of Texas, Austin, U.S.A.
There are many indications that the contralateral hemisphere contributes to recovery from cortical lesions in rats. Here, we examine how a second contralateral cortical lesion, inflicted after the first, affects the functional recovery.
A focal brain lesion with a diameter of about 2 mm was induced by means of a photothrombosis in the forelimb area (FL-SMC). A second lesion was induced in the contralateral FL-SMC, either simultaneously or 2, 7 or 10 days after the first lesion. Functional recovery was tested in two ways: (1) by rearing rats in a glass cylinder and counting the number of forelimb movements along the wall; and (2) by counting 'foot faults' while the rats were walking on a grid. In both cases, we scored the number of steps in the impaired limb compared to controls.
These tests revealed acute functional deficits in the impaired limb after the first lesion was made. One day after surgery, rats preferred the healthy limb for moving along the wall and made many false steps with the impaired limb when walking on the grid. Inflicting a second (contralateral) lesion after a few days caused a functional deficit in both forelimbs. Recovery in these animals was delayed compared to animals with only one lesion. Inflicting a second lesion after longer periods (10 days) revealed a residual deficit of the compensated limb.
This investigation shows that: (i) acute motor deficits can be demonstrated with focal lesions in the sensorimotor cortex; and (ii) a subsequent lesion, induced during the process of recovery, delays the compensation.
Supported by DFG, 194 B2 and Neurograduiertenkolleg.
Paper presented at Measuring Behavior 2002 , 4th International Conference on Methods and Techniques in Behavioral Research, 27-30 August 2002, Amsterdam, The Netherlands