RESUMO
OBJECTIVES: This study aimed at clarifying the character of cerebral artery vasospasm on rabbit model by observing the vascular responses to nitric oxide and endothelin-1 treatment at different time points. MATERIALS AND METHODS: Twenty-eight rabbits undertook vertebrobasilar angiographies on the postoperative 2nd day and the 7th day after subarachnoid hemorrhage operation. The animals were divided into the vasospasm and the non-vasospasm group accroding to the result of vertebrobasilar angiographies. After sacrificing the animal, the vascular ring of harvested basilar artery was suspended in Krebs solution organ chamber for observation of isometric tension change in response to nitric oxide (NO) and endothelin-1 under high (95% O2 / 5% CO2) and low (95% N2 / 5% CO2) O2 tension. To investigate NO-dependent the vascular relaxation response, acetylcholine (10-7-3x10-4 M) was applied to basilar artery ring preconcentrated with histamine (10-6-10-5 M) in the organ chamber. The vascular contraction response was observed by applying endothelin-1 (10-11-3x10-8 M) into the organ chamber. RESULTS: The angiography showed vasospasm in seven of fifteen rabbits of the postoperative-2-day group (64.3+/-11.2%) and seven of fifteen rabbits of the postoperative-7-day (64.9+/-10.9%). On the postoperative-2-day, all the vascular response to NO and endothelin-1 under both high and low O2 tension was not significantly different between the vasospasm developed basilar artery and the vasospasm undeveloped one. On the postoperative-7-day, the vascular relaxation response to NO under high O2 tension was significantly different between the vasospasm developed basilar artery and the vasospasm undeveloped one (p=0.029). However, the vascular relaxation response to NO under low O2 tension was not significantly different. The vascular contraction response to endothelin-1 under high O2 tension was significantly different between the vasospasm developed basilar artery and the vasospasm undeveloped one (p=0.032). However, the vascular contraction response to endothelin-1 under low O2 tension was not significantly different. CONCLUSION: This experiment suggest that the vasospasm of the postoperative-2-day have different character from that of the postoperative-7-day in the rabbits. This suggestion may play some roles in the future study of the subarachnoid hemorrhage model. the study of the vasospasm mechanism of human, and developing antispasmodic drugs.