α2—肾上腺素体介导大鼠主动脉收缩的特性

为阐明功能性α2－肾上腺素受体（α2－AR）的特性及其与α1－AR的相互关系，以离体大鼠主动脉为模型，进行收缩功能实验，发现在大鼠主动脉中，α1－AR和α2－AR产可介导其收缩效应并以α1－AR折作用为主，α1－AR可增强α2－AR介导的收缩效应，而α2－AR则对α1－AR介导的收缩效应无影响，在不可逆阻断α1－AR而保留α2－AR的条件下，α2－AR介导的缩血管效应消失，仅在阈值浓度的KCl存在下才能显示，且收缩幅度较对照组显著降低，结果表明，在离体大鼠主体动脉中存在功能性α2－AR，α2－AR的缩血管作用依赖于α1－AR的激动，其最大收缩反应远远小于α1－AR。

Characteristics of alpha2-adrenoceptor mediated contractile response in isolated aortae of rats

In order to investigate the characteristics of vascular alpha(2)-adrenoceptor (alpha(2)-AR) and its relation to alpha(1)-AR, isolated Wistar rat (10 weeks) aortae were used as a model for testing contractile function in vivo. It was found that both alpha(1) and alpha(2)-AR (mainly alpha(1)-AR) mediated the contractile response. While alpha(1)-AR enhanced the contractile response mediated by alpha(2)-AR, alpha(2)-AR had no effect on that mediated by alpha(1)-AR. When alpha(1)-AR was irreversibly blocked and the activity of alpha(2)-AR remained intact, the contractile response mediated by alpha(2)-AR was no longer observed. The contractile response only reappeared in the presence of KCl of the threshold level, and the extent of the maximum contraction decreased, compared with control (with alpha(1)-AR being intact). The results show that there exists a functional alpha(2)-AR in rat aorta, however, the contractile effect of which depends on the stimulation of alpha(1)-AR.