Hill-Venning C, Peters J A, Callachan H, Lambert J J, Gemmell D K, Anderson A, Byford A, Hamilton N, Hill D R, Marshall R J, Campbell A C
Department of Pharmacology and Clinical Pharmacology, Ninewells Hospital and Medical School, Dundee, U.K.
Neuropharmacology. 1996;35(9-10):1209-22. doi: 10.1016/s0028-3908(96)00069-x.
The anaesthetic profile of a novel water-soluble aminosteroid, Org 20599 [(2 beta, 3 alpha, 5 alpha)-21-chloro-3-hydroxy-2-(4-morpholinyl)pregnan-20-one methanesulphonate], and the ability of the compound to allosterically regulate the activity of the GABAA receptor, have been studied in comparison to the properties of established intravenous general-anaesthetic agents. Intravenously administered Org 20599 produced a rapid onset, short duration loss of the righting reflex in mice. The anaesthetic potency of Org 20599 was comparable to that of the steroids 5 alpha-pregnan-3 alpha-ol-20-one or alphaxalone, and exceeded that of propofol, thiopentone or pentobarbitone. Org 20599 and the reference anaesthetic agents allosterically displaced the binding of [35S]-t-butylbicyclophosphorothionate (TBPS) from GABAA receptors of rat-brain membranes with the order of potency: 5 alpha-pregnan-3 alpha-ol-20-one > Org 20599 > alphaxalone > propofol > thiopentone > pentobarbitone. At human recombinant alpha 1, beta 2, gamma 2L subunit-containing GABAA receptors expressed in Xenopus laevis oocytes, the anaesthetic agents produced a concentration-dependent and reversible potentiation of the peak amplitude of GABA-evoked currents. A similar positive allosteric action of Org 20599 was observed for the GABAA receptors expressed by bovine adrenal chromaffin cells maintained in culture. The rank order of potency in the aforementioned assays was identical to that determined from the displacement of TBPS binding. At concentrations greater than those required for potentiation of GABA, the anaesthetics exhibited GABA-mimetic effects with a rank order of potency that paralleled their modulatory activity. Such direct agonism varied greatly in maximal effect between compounds. The modulatory and direct agonist actions of Org 20599 were additionally confirmed utilizing rat hippocampal neurones in culture. The results indicate Org 20599 to be a potent and short-acting intravenous anaesthetic agent in mice and suggest positive allosteric regulation of GABAA receptor function to be a plausible molecular mechanism of action for the drug.
一种新型水溶性氨基甾体Org 20599 [（2β，3α，5α）-21-氯-3-羟基-2-（4-吗啉基）孕烷-20-酮甲磺酸盐]的麻醉特性，以及该化合物变构调节GABAA受体活性的能力，已与已确立的静脉全身麻醉剂的特性进行了比较研究。静脉注射Org 20599可使小鼠快速出现并短暂丧失翻正反射。Org 20599的麻醉效力与甾体5α-孕烷-3α-醇-20-酮或阿法沙龙相当，且超过丙泊酚、硫喷妥钠或戊巴比妥。Org 20599和参比麻醉剂能变构取代大鼠脑膜GABAA受体上的[35S]-叔丁基双环磷硫代酸盐（TBPS）结合，效力顺序为：5α-孕烷-3α-醇-20-酮>Org 20599>阿法沙龙>丙泊酚>硫喷妥钠>戊巴比妥。在非洲爪蟾卵母细胞中表达的人重组含α1、β2、γ2L亚基的GABAA受体上，麻醉剂产生浓度依赖性且可逆的GABA诱发电流峰值幅度增强。对于培养的牛肾上腺嗜铬细胞表达的GABAA受体，也观察到Org 20599有类似的正变构作用。上述试验中的效力顺序与从TBPS结合取代测定中确定的顺序相同。在高于增强GABA所需浓度时，麻醉剂表现出GABA模拟效应，其效力顺序与其调节活性平行。不同化合物之间这种直接激动作用的最大效应差异很大。利用培养的大鼠海马神经元进一步证实了Org 20599的调节作用和直接激动作用。结果表明Org 20599在小鼠中是一种强效短效静脉麻醉剂，并提示GABAA受体功能的正变构调节是该药物可能的分子作用机制。
