Investigation of occurrence of lateralization in response to an ischemic stroke in rats

Stroke is the third leading cause of death in western industrialized countries. After stroke, neurons at risk for infarction may only survive for few hours and the opportunity for effective therapeutic intervention is accordingly small. A better understanding of the progression of stroke is therefore essential in the optimization and alteration of current clinical treatment options and therapeutic strategies. The objective of this work was to investigate if changes occur in the hemisphere contralateral to an ischemic stroke in the hyperacute phase (les 5 hours). A photothrombosis rat model was used to record electrophysiological responses to an ischemic stroke. Ischemic stroke was induced in four rats and two rats were serving as controls. In the hemisphere contralateral to an ischemic stroke we observed a transient period, where the cortical firing decreased after ischemic onset. This decrease was observed in three rats, occurred 10-120 min after ischemic onset, and lasted for 10- 120 min. Furthermore, we observed events of hyperexcitability in two rats. The hyperexcitability occurred about 30 min after ischemic onset and lasted throughout the experiments. The results indicated that lateralization occurs in the hyperacute phase of stroke. The findings should, however, be substantiated by further studies, e.g. including simultaneous measurements from both brain hemispheres.