Electrophysiological transcortical diaschisis after middle cerebral artery occlusion (MCAO) in rats.

Remote changes in brain function following stroke are called diaschisis. These remote effects may contribute to the neurological deficit following brain infarction; in addition they may lead to post-stroke epilepsy and affect functional recovery. In the present study we addressed the question of whether an increase in excitability can be observed contralateral to middle cerebral artery (MCA) infarction. Permanent occlusion of the middle cerebral artery (MCAO) was induced experimentally in rats with an intraluminal silicon-coated filament. Seven days later, brain excitability was tested with extracellulare recording techniques in neocortical coronal brain slices using a paired-pulse stimulus protocol. In rats with MCAO, excitability was increased in the neocortex contralateral to the infarction compared with the control group. These alterations extended through wide parts of the contralateral neocortex. The study demonstrates that MCAO causes transcallosal electrophysiological diaschisis. Together with results obtained previously with photothrombotic cortical lesions, it can be concluded that these remote effects are not due to characteristics of the individual lesion model, but are common consequences of brain lesions.