Differential uptake of 3H-thymidine by structures of the pia-arachnoid and cerebral cortex distal to the interrupted middle cerebral artery.

Tritiated thymidine accumulated in pial surface structures 1-10 days after interruption of the right middle cerebral artery (MCA) in the rat. Essentially no radioactive marker was present in the underlying cortical territory of the interrupted MCA other than at the operation site. Control meninges, cortex contralateral to the operated MCA, and structures proximal to the operation site were without appreciable accumulation of 3H-thymidine. Thus, the marked cellular proliferative response to MCA interruption was localized to structures of the pia-arachnoid overlying the cortical territory of the interrupted MCA. The data suggest that after MCA occlusion a cellular proliferative response contributes to the expansion of preexisting pial surface collateral vessels and that the expansion does not extend into the parenchyma.