The permeability change of major cerebral arteries in experimental vasospasm

The influence of vasospasm on the permeability of the major cerebral arteries was studied using horseradish peroxidase (HRP). Experimental vasospasm was produced in canine basilar arteries by successive injections, 2 days apart, of autologous blood into the cisterna magna. HRP was injected intravenously or intracisternally 48 hours after the second injection of autologous blood, and all animals were killed by perfusion fixation 60 minutes after the injection of HRP. The distribution of HRP was observed by transmission electron microscopy. In 10 dogs injected intracisternally with HRP, 5 control dogs demonstrated a moderate amount of HRP in the intermuscular space through the adventitia. Five dogs with subarachnoid hemorrhages (SAHs) showed a moderate amount of HRP in the intermuscular space. In 11 dogs injected intravenously with HRP, 5 control dogs showed no leakage of HRP into vessel walls. Six dogs with SAHs showed HRP in the interendothelial space. These findings suggest that, despite SAHs, HRP seems to be able to circulate in the cerebrospinal fluid and makes contact with the cerebral vessels. This study suggests the possibility that spasmogenic substances may penetrate the vessel wall from the extraluminal side more easily than from the intraluminal side.