Simpson L L
J Pharmacol Exp Ther. 1975 Feb;192(2):365-71.
The pithed rat preparation has been used to study the sympathomimetic activity of 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (TIQ). In this preparation, an increase in blood pressure is indicative of alpha stimulation, and an increase in heart rate is indicative of beta stimulation. Using this preparation, we have found that TIQ is approximately 3 orders of magnitude less potent than norepinephrine in evoking changes in blood pressure and heart rate. The activity of TIQ has also been studied in pithed animals which had been previously sympathectomized with 6-hydroxydopamine. Sympathectomy produced a marked reduction in cardiac norepinephrine, and it nearly abolished vascular responses to injected tyramine. Following sympathectomy, pithed animals were supersensitive to norepinephrine and subsensitive to TIQ. Similar results were obtained on pithed animals that had been pretreated with cocaine. It is concluded that TIQ is a weak sympathomimetic agent possessing both directly and indirectly acting properties. The data are discussed in terms of a proposal that TIQ may be a false adrenergic transmitter.
脊髓毁损大鼠制备模型已被用于研究6,7 - 二羟基 - 1,2,3,4 - 四氢异喹啉（TIQ）的拟交感活性。在该制备模型中，血压升高表明有α受体激动作用，心率加快表明有β受体激动作用。利用此制备模型，我们发现TIQ在引起血压和心率变化方面的效力比去甲肾上腺素约低3个数量级。TIQ的活性也在先前用6 - 羟基多巴胺进行过交感神经切除术的脊髓毁损动物中进行了研究。交感神经切除术使心脏去甲肾上腺素显著减少，并且几乎消除了对注射酪胺的血管反应。交感神经切除术后，脊髓毁损动物对去甲肾上腺素超敏，对TIQ则低敏。在用可卡因预处理过的脊髓毁损动物上也得到了类似结果。结论是TIQ是一种弱拟交感剂，兼具直接和间接作用特性。根据TIQ可能是一种假性肾上腺素能递质这一假说对数据进行了讨论。
