Prevention of vasospasm in penetrating arteries with MAPK inhibitors in dog double-hemorrhage model.

BACKGROUND

Vasospasm in the penetrating arteries contributes to ischemic neurological deficit. It may be as important as angiographic vasospasm because it would explain the discrepancies between angiographic vasospasm and clinical symptoms in some patients. It may also underlie the different effects of vasodilators. The present study examined this hypothesis by looking at the effect of the inhibitors of mitogen-activated protein kinase (MAPK) on vasospasm of the penetrating arteries.

METHODS

Twenty-two adult mongrel dogs of either sex were used for the dog double-hemorrhage model. The dogs were randomly divided into four groups: control-hemorrhage, vehicle-treated, PD98059-treated, and U0126-treated groups. The drug injections were started on Day 3 after the first subarachnoid hemorrhage (SAH). The clinical status of the dogs was studied, based on their activity, appetite, and focal neurological symptoms. On Day 7, all the dogs were sacrificed, and the penetrating arteries from the brain stem were prepared for transmission electron microscopy.

RESULTS

(1) Severe vasospasm developed in the basilar arteries in the SAH-without-treatment group (control), in the DMSO-treated group (DMSO), and in the U0126 treatment group with mean reduction of the basilar artery diameter of 46.57%, 49.3%, and 39.6%, respectively. In the PD98059-treatment group only a mild vasospasm was observed and the mean reduction of the basilar artery diameter was 18.9%. (2) All the dogs in the control SAH and vehicle-treated groups developed severe angiographic and clinical vasospasm. The penetrating arteries were contracted, and the endothelial and smooth muscle cells were dystrophic. (3) The dogs in the U0126-treated group developed severe angiographic, but not clinical, vasospasm. The penetrating arteries were not contracted, and the endothelial and smooth muscle cells were not dystrophic. (4) The dogs in the PD98059 group developed mild angiographic vasospasm. No dog developed clinical symptoms that could be attributed to vasospasm. In morphological studies, the penetrating arteries were slightly contracted, but the cells were not dystrophic.

CONCLUSIONS

Vasospasm of the penetrating arteries, but not angiographic vasospasm, is consistent with the clinical symptoms and signs of vasospasm. MAPK may be important in maintaining vasospasm of both major and penetrating cerebral arteries. The correlation of the improvement in the clinical score with the reduction of vasospasm in the penetrating arteries demonstrated an important role of penetrating arteries in the morbidity and mortality caused by SAH.