Long-term functional outcome following transient middle cerebral artery occlusion in the rat: correlation between brain damage and behavioral impairment.

The assessment of both histological and functional long-term outcomes after cerebral ischemia is increasingly recommended for preclinical studies. Whereas correlations between behavioral impairments and primary ischemic lesion are documented, little is known about their relationships with remote nonischemic regions that undergo secondary degeneration, such as the thalamus. Anesthetized rats were subjected to mild (30 min) or severe (60 min) occlusion of the middle cerebral artery. Two months after ischemia, sensorimotor behavior was assessed according to the neurological score, limb-placing, adhesive-removal, and staircase tests; the final histological lesion was measured after this assessment. Cortical damage was correlated to all transient and long-lasting sensorimotor deficits, whereas striatal lesion was more consistently reflected by the forelimb-placing reflexes and adhesive-removal motor deficits. By contrast, the thalamic atrophy was not correlated to early neurological impairment, but rather to the late sensory deficit at the adhesive-removal test and to the skilled forepaw reaching alteration at the staircase test. This suggests that thalamus contributes, albeit moderately, to the ischemia-induced long-lasting sensorimotor deficits, some of which represent relevant targets for therapeutic interventions.