Changes in Vascular Responses of Basilar Artery to Vasodilators and Vasoconstrictors in Experimental Vasospasm Model Rabbits

토끼의 뇌혈관 연축 모델에서 혈관확장제 및 혈관수축제에 대한 기저동맥의 감수성 변화

Objective : This experiment is aimed at clarifying the characteristics of spasmodic basilar arteries in the rabbits of subarachnoid hemorrhage(SAH) with observation of vascular response to nitric oxide(NO) and endothelin-1. Material and Methods : Seventy-nine New Zealand white rabbits were divided into 4 groups : control(n=17), sham operation(n=13), postictal-2-day(n=25), and postictal-7-day group(n=24). Rabbits in the postictal-2-day group and postictal-7-day group underwent transfemoral vertebral angiography 2 days and 7 days after SAH respectively. A vascular ring of spasmodic basilar artery was harvested and suspended in organ chamber($37^{\circ}C$) to observe isometric tension changes in response to NO and endothelin-1 under both high(95% $O_2$/5% $CO_2$) and low(95% $N_2$/5% $CO_2$) $O_2$ tension. To investigate the vascular response to NO, acetylcholine from $10^{-7}M$ to $3{\times}10^{-4}M$ concentration was applied to basilar artery ring precontracted with histamine $10^{-6}-10^{-5}M$ in the organ chamber. The vascular response to endothelin-1 was observed by applying endothelin-1 from $10^{-11}M$ to $3{\times}10^{-8}M$ concentration into organ chamber. Results : Seven of 15 live rabbits which underwent angiography 2 days after SAH, were confirmed to develop vasospasm($64.3{\pm}11.2%$) whereas seven of 13 live rabbits which underwent angiography 7 days after SAH, were confirmed to develop vasospasm($64.9{\pm}10.9%$). In all groups, hypoxia significantly reduced the vascular relaxation of basilar arteries to NO. However, hypoxia made no influence on the vascular contraction of basilar arteries to endothelin-1 in all groups. In vascular relaxation of basilar arteries to NO under high $O_2$ tension between groups, the maximum relaxation of basilar arteries in the postictal-7-day group was significantly reduced compared to the postictal-2-day group. In vascular contraction of basilar arteries to endothelin-1 under high $O_2$ tension between groups, the maximum contraction of basilar arteries in the postictal-7-day group was significantly reduced compared to the postictal-2-day group. Conclusions : This experiment suggests that the characteristics of vascular response to NO and endothelin-1 in the spasmodic basilar arteries of rabbits observed 2 days after SAH is different from those observed 7 days after SAH.