Disturbance in the intramural circulation of the major cerebro-pial arteries after experimental subarachnoid haemorrhage.

The intramural fluid circulation of the cerebral arterial wall was investigated using horseradish peroxidase (HRP) as a tracer which was injected intravenously or intracisternally in dogs with or without subarachnoid haemorrhage (SAH). In the control dogs, the endothelial barrier function was confirmed for intravenous HRP, whereas the intracisternal HRP passed freely through the interstitial spaces of the adventitia and media to reach the intima within a few minutes. However, on the 5th day after SAH the barrier function of the intima for intravenous HRP was lost. In addition, there was a marked decrease in the amount of HRP reaching the intima when injected intracisternally. The intercellular space appears to be the main route for leakage of HRP into the subendothelial layer from the arterial lumen. Obstruction of the interstitial space in the adventitia by blood elements may be the cause of the disturbed intramural circulation of cerebrospinal fluid. These results suggest that this disturbance in the intramural circulation of the cerebral arterial wall plays a role in the development and/or progression of delayed cerebro-arterial narrowing after SAH.