Experimental models of subarachnoid hemorrhage in the rat: a refinement of the endovascular filament model

A new experimental model in rats for study of the pathophysiology of subarachnoid hemorrhage

A new experimental model of subarachnoid hemorrhage (SAH) in rats is described. A needle was stereotaxically placed in the prechiasmatic cistern and 300, 250 or 200 microl of blood was injected manually, keeping the intracranial pressure (ICP) at the mean arterial blood pressure (MABP) level. An acceptable mortality was observed only after injection of 200 microl of blood. In this group, MABP and ICP increased immediately after SAH, but soon approached baseline levels. The subarachnoid blood was mainly distributed in the basal cisternal system and its estimated volume was about 95% of the amount injected. This new model resembles clinical SAH, is very reproducible, easy to use and seems to be a suitable model for studies of the pathophysiology of SAH.

Comparison of three rat models of cerebral vasospasm

A substantial number of rat models have been used to research subarachnoid hemorrhage-induced cerebral vasospasm; however, controversy exists regarding which method of selection is appropriate for this species. This study was designed to provide extensive information about the three most popular subarachnoid hemorrhage rat models: the endovascular puncture model, the single-hemorrhage model, and the double-hemorrhage model. In this study, the basilar artery and posterior communicating artery were chosen for histopathological examination and morphometric analysis. Both the endovascular puncture model and single-hemorrhage model developed significant degrees of vasospasm, which were less severe when compared with the double-hemorrhage model. The endovascular puncture model and double-hemorrhage model both developed more vasospasms in the posterior communicating artery than in the basilar artery. The endovascular puncture model has a markedly high mortality rate and high variability in bleeding volume. Overall, the present study showed that the double-hemorrhage model in rats is a more suitable tool with which to investigate mechanism and therapeutic approaches because it accurately correlates with the time courses for vasospasm in humans.

Mouse model of subarachnoid hemorrhage associated cerebral vasospasm: methodological analysis

The transgenic mouse has been used to study subarachnoid hemorrhage (SAH) induced delayed cerebral vasospasm (DCV). Methodological parameters have not been analyzed to validate this model and associated neurological deficits have not been described. We introduce a technique to quantify DCV and associated neurological deficits. C57BL/6J mice were subjected to SAH or sham surgery. Seventy-two hours later, the vasculature was cast in situ with India ink/gelatin at perfusion pressures of 40-60, 60-80, or 100-120 mmHg. Mice were perfused with and without microfiltration. Additional mice underwent grading of SAH size, measurement of vascular diameters, and neurological examination (score range 5-27; 27= normal). When cast at 60-80 mmHg, SAH was associated with an intraluminal cross-sectional diameter reduction in 3 of 7 ipsilateral vascular segments. At 40-60 mmHg, the diameter of only one segment was reduced. No changes were observed at 100-120 mmHg. Emboli prevented adequate perfusion of vascular segments in the absence of microfiltration. Median (interquartile range) neurologic score was reduced after SAH (sham, 27(27); SAH 11(7-17)). Deficits correlated with middle cerebral artery (MCA) diameter and SAH grade. MCA diameter also correlated with SAH grade. Only when utilizing microfiltration, controlling for hemorrhage size, and casting at perfusion pressures of 60-80 mmHg does India ink/gelatin vascular casting demonstrate consistent DCV that correspnds to neurological deficits. This allows measurement of both anatomical and clinical DCV in the mouse.

Microvascular endothelial dysfunction and its mechanism in a rat model of subarachnoid hemorrhage

After subarachnoid hemorrhage (SAH), large cerebral arteries are prone to vasospasm. Using a rat model of SAH, we examined whether cortical microvessels demonstrate vasomotor changes that may make them prone to spasm and whether endothelial dysfunction may account for any observed changes. Two days after percutaneous catheterization into the cisterna magna, 0.3 mL of autologous blood was injected into the subarachnoid space. The brain tissue was harvested 20 min later, and microvessels were dissected from the parietal cortex. Vasomotor responses to the thromboxane analog U46619, the protein kinase C agonist phorbol acetate, endothelin-1, adenosine diphosphate, nitroprusside, and isoproterenol were examined in vitroin cerebral arterioles from the control, sham-operated, and SAH animals. Endothelial nitric oxide synthase (NOS3) messenger RNA and protein concentration was measured by northern and western blotting, respectively. Arterioles from the SAH animals demonstrated attenuated dilation to the endothelium-dependent dilator adenosine diphosphate and accentuated constriction to endothelin-1, while responses to the other agents tested were unchanged. NOS3 protein concentration was decreased, but NOS3 messenger RNA was increased after SAH. After SAH, cortical arterioles demonstrate endothelial dysfunction, which may be the basis for microvascular spasm. This is in part related to decreased NOS3, which occurs despite an increase in its transcription.

IMPLICATIONS

Acute microvascular endothelial dysfunction may occur after subarachnoid hemorrhage and contribute to microvascular spasm.