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左旋四氢巴马汀(I-THP)选择性地抑制~8H-prazosin和~3H-clo-nidine与大鼠脑细胞膜上α_1和α_2肾上腺素受体的结合,与α_1、α_2受体的亲和力(Pki)分别为5.84和5.87。其拮抗苯肾上腺素收缩大鼠离体主动脉条作用PA_2值为5.59,它使利血平化大鼠出现升压效应,并为育亨宾所阻滞。大剂量I-THP能拮抗可乐定的升压作用,表明I-THP有阻滞α_1受体的作用,小剂量时能激动突触前膜α_2受体,大剂量亦能阻滞突触后的α_2受体。
L-tetrahydropalmatine (I-THP) selectively inhibited the binding of ~ 8H-prazosin and ~ 3H-clo-nidine to the α_1 and α_2 adrenergic receptors on rat brain cell membranes with the affinity to α_1, α_2 receptors (Pki) were 5.84 and 5.87 respectively. The antagonistic phenylephrine contraction of aortic strips in vitro PA_2 value of 5.59, it reserpine-induced rat vasopressor effect, and blocked by yohimbine. High-dose I-THP antagonized clonidine’s potentiation, indicating that I-THP has the effect of blocking the α_1 receptor and can activate the pre-synaptic membrane α_2 receptor at a low dose, and blocking the post-synaptic α_2 receptor.