Dextran decreases extracellular tortuosity in thick-slice ischemia model

An unexpected decrease of extracellular space (ECS) tortuosity was recently reported in thick(1000 mu m) ischemic slices using radiotracers. The curre nt study shows that the tortuosity in thick slices from rat neocortex can i ncrease or decrease depending on experimental conditions, whereas ECS volum e fraction remains diminished to approximately 10%. Using diffusion of tetr amethylammonium, it was found that tortuosity rose from a normoxic value of 1.66 to 1.99 in thick slices. However, tortuosity dropped to 1.54 when dex tran (70,000 molecular weight) was added to the bathing medium. The current results show that dextran enhances diffusion in thick ischemic slices with out increasing the size of the ECS.