Brown M J, Struthers A D, Di Silvio L, Yeo T, Ghatei M, Burrin J M
Clin Sci (Lond). 1985;68 Suppl 10:137s-139s. doi: 10.1042/cs068s137.
Six healthy volunteers received a 60 min infusion of guanfacine (alpha 2-agonist) on two occasions, preceded by either idazoxan (alpha 2-antagonist) or vehicle. Idazoxan elevated blood pressure by 8/7 mmHg, but there was no change on either day during guanfacine infusion. Guanfacine reduced plasma noradrenaline by approximately 30%, and this was not antagonized by idazoxan. By contrast, the 30-fold increase in plasma growth hormone caused by guanfacine was almost completely blocked by idazoxan. Guanfacine caused a two- to three-fold increase in plasma glucagon and a similar reduction in plasma insulin. Only the latter was antagonized by idazoxan. No consistent changes in plasma ACTH were observed after either idazoxan or guanfacine. Idazoxan itself elevated plasma noradrenaline up to twice baseline values, but did not affect the other metabolic measurements. alpha 2-Adrenoceptor stimulation plays a minor role in control of hormone release but has a greater physiological role in regulating release of the neurotransmitter, noradrenaline.
六名健康志愿者在两种情况下接受了60分钟的胍法辛（α2激动剂）输注，一种情况先给予咪唑克生（α2拮抗剂），另一种情况先给予赋形剂。咪唑克生使血压升高8/7 mmHg，但在输注胍法辛的任何一天血压均无变化。胍法辛使血浆去甲肾上腺素降低约30%，且未被咪唑克生拮抗。相比之下，胍法辛引起的血浆生长激素30倍的升高几乎完全被咪唑克生阻断。胍法辛使血浆胰高血糖素升高两到三倍，使血浆胰岛素降低类似幅度。只有后者被咪唑克生拮抗。在给予咪唑克生或胍法辛后，未观察到血浆促肾上腺皮质激素有一致的变化。咪唑克生本身使血浆去甲肾上腺素升高至基线值的两倍，但不影响其他代谢指标。α2肾上腺素能受体刺激在激素释放控制中起次要作用，但在调节神经递质去甲肾上腺素的释放中具有更大的生理作用。
