Improved rat model for cerebral vasospasm studies.

While the rat has been used extensively in subarachnoid hemorrhage (SAH)-cerebral vasospasm studies, concerns exist whether this animal represents a usable model because its time course and pattern of cerebral vasospasm following SAH is not comparable to that observed in man. At present, our knowledge of the rat model is based almost exclusively on studies using a 'single hemorrhage' method. Since there is a positive correlation between severity of cerebral vasospasm, and volume of subarachnoid blood, an obvious question is whether the rat will show modifications in vascular responses when insulted by a second SAH. Here, an SAH was produced in rats using a 'double hemorrhage' method. Following SAH, cerebral arteries showed pathological alterations, significant decreases in luminal perimeter, and increases in arterial wall thickness, over a 7-day post-SAH period. The above vascular features are considered to be indicative of cerebral vasospasm and their presence over a 7-day post-SAH period represents a significant time extension when compared to a single hemorrhage. These modified vascular responses made the double hemorrhaged rat a much-improved animal model.