Recovery of sensorimotor function after distal middle cerebral artery photothrombotic occlusion in rats

The purpose of the present study was to delineate the behavioral correlates of focal thrombotic occlusion of the distal middle cerebral artery in rats and to compare the pattern of deficits and subsequent recovery to that following proximal middle cerebral artery occlusion.

Ten Sprague-Dawley rats underwent photothrombotic occlusion of the distal middle cerebral artery with tandem occlusion of the common carotid arteries (dMCAO group); 10 animals served as operated controls. Beginning on postischemia day 2, animals were given a battery of five tests that assessed sensorimotor integration, attentional mechanisms, and muscle strength; testing continued twice weekly until day 30. Nine days of cognitive testing on the learning set of the water maze task were then given. Infarct volume and hemispheric atrophy were determined for each dMCAO animal.

After ischemia, the dMCAO group exhibited significant behavioral deficits in posture reflex, ability to place a forelimb to various stimuli, limb adduction during rearing, and neglect of contralateral space. These deficits showed variable recovery rates. No deficits were observed in muscle strength or cognitive performance. The deficits and patterns of recovery were related to infarct location and to degree of hemisphere atrophy.

The present study suggests that a battery of tests is necessary to fully characterize the pattern of behavioral deficits after focal cerebral ischemia. Location of infarct damage and associated degree of hemispheric atrophy were important variables in determining behavioral outcome. The present results are compared with those of the more traditional model of electrocoagulation of the proximal middle cerebral artery.