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AIM: In an attempt to pharmacologically characterize the Chinese antihypertensive drug, tetrandrine, we observed in rat-tail arteries, an unusual contraction in tissues that were stimulated with high [KCI] and not those stimulated with phenylephrine. The characteristics of this contraction were studied. METHODS: Segments of perfused ventral rat-tail arteries (RTA) were contracted with a depolarizing concentration (120 mmol/L) of KCI or with phenylephrine (3.0 umol/L). At peak contraction, they were exposed to tetrandrine (40 umol/L), which caused marked relaxation in each case. Washing the RTA led to an unusual, slowly-declining contraction, hereafter referred to as tetrandrine-induced contraction (TIC) which was also observed when the tissues were exposed to 80 umol/L, but not 10 umol/L or 20 umol/L of tetrandrine. RESULTS: Pretreatment with phentolamine (non-selective a-adrenoceptor antagonist), prazosin (selective aradrenoceptor antagonist) or 6-hydroxydopamine (for denervation), but not rauwolscine
AIM: In an attempt to pharmacologically characterize the Chinese antihypertensive drug, tetrandrine, we observed in rat-tail arteries, an unusual contraction in tissues that will stimulate with high [KCI] and not those stimulated with phenylephrine. The characteristics of this contraction were studied. . METHODS: Segments of perfused ventral rat-tail arteries (RTA) were contracted with a depolarizing concentration (120 mmol/L) of KCI or with phenylephrine (3.0 umol/L). At peak contraction, they were exposed to tetrandrine (40 umol /L), which challenge marked relaxation in each case. Washing the RTA led to an unusual, slowly-declining contraction, hereafter referred to as tetrandrine-induced contraction (TIC) which was also observed when the individuals were exposed to 80 umol/L , but not 10 umol/L or 20 umol/L of tetrandrine. RESULTS: Pretreatment with phentolamine (non-selective a-adrenoceptor antagonist), prazosin (selective aradrenoceptor antagonist) or 6-hydroxydopamine (for denervation), bu t not rauwolscine