Does vasospasm occur in small pial arteries and arterioles of rabbits?

Vasospasm is a serious complication associated with subarachnoid hemorrhage. Successful management of vasospasm will ultimately depend on a clear understanding of the scope of this phenomenon, including whether arterial elements of different calibers are equally affected. We therefore examined the responses to subarachnoid hemorrhage in rabbit basilar arteries, small pial arteries, and arterioles. We compared the brain stem pial arteries of 10 perfusion-fixed male New Zealand White rabbits after experimental subarachnoid hemorrhage to those of five control rabbits using morphological analysis of cross-sections of plastic-embedded vessels. After subarachnoid hemorrhage, the internal elastic lamina was highly corrugated in all basilar arteries (mean diameter 319 +/- 51 microns). These arteries were severely constricted in comparison with the control group, in which the mean diameter was 691 +/- 17 microns, and corrugation of the internal elastic lamina was not present. In contrast, small pial arteries and arterioles very rarely demonstrated a vasoconstrictive configuration after subarachnoid hemorrhage. The contractility of the smaller vessels was confirmed by injecting 2 mg/kg BaCl2 intracisternally. Following BaCl2 injection, corrugation of the internal elastic lamina was detected in the small arteries and arterioles as well as the basilar arteries. We conclude that experimental chronic vasospasm after subarachnoid hemorrhage in rabbits tends to occur in large conducting arteries rather than in smaller pial arteries and arterioles.