毒理性
乌头碱(MA)是乌头属植物生物碱之一。乌头属植物生物碱的主要毒性作用于心脏和中央神经系统。它们可以诱发心房颤动或心室颤动、室性心律失常,以及在神经刺激后引起重复的后电位和振荡。乌头碱引发心律失常的电生理机制是动作电位的最终复极化阶段延迟,这会引发过早或触发的兴奋。这是由于去除了电压依赖性Na+通道的失活。由于Na+的大量流入,兴奋之后是神经细胞的完全不可兴奋性。乌头属植物生物碱能促使多巴胺能神经元释放多巴胺;然后过度的细胞外多巴胺对细胞抗氧化系统造成压力并诱导神经元凋亡。它们是已知的心脏毒素和神经毒素,并且还具有胚胎毒性和细胞毒性。(A15426)去甲乌药碱激活下行抑制途径的抑制性去甲肾上腺素能神经元。去甲乌药碱能够在低浓度下产生持久的兴奋作用,在高浓度下产生抑制作用,并在中等浓度范围内产生双向作用,这可能是通过涉及去甲肾上腺素系统。在应用30和100 nM去甲乌药碱时观察到的双向作用类似于大鼠海马CA1区域中去甲肾上腺素的作用。事实上,通过预先使用a-和b-肾上腺素能受体拮抗剂可以选择性地预防30和100 nM去甲乌药碱以双向方式诱发的两种不同作用,这为这些效果涉及激活a-和b-受体提供了证据。(A15427)
Mesaconitine (MA) is one of the Aconitum sp. alkaloids. The primary toxicity of Aconitum sp. alkaloids is on the heart and the central nervous system. They can induce cardiac flutter or fibrillation, ventricular arrhythmias, and repetitive after-potentials and oscillations following nerve stimulation. The electrophysiological mechanism of the arrhythmogenic effect of aconitine is a delay in the final repolarization phase of the action potential, which initiates premature or triggered excitations. These are due to a removal of inactivation of voltage-dependent Na+ channels. Due to the massive influx of Na+, the excitation is followed by complete inexcitability of nerve cells. Aconitum sp. alkaloids evoke dopamine release from dopaminergic neurons; then excessive extracellular dopamine creates stresses on cellular antioxidant systems and induces neuron apoptosis. They are known cardiotoxins and neurotoxins, and also have embryotoxicity and cytotoxicity. (A15426) Mesaconitine activates inhibitory noradrenergic neurones of descending inhibitory pathways. Mesaconitine is capable of evoking a long-lasting excitatory action at a low concentration, a depressant action at high concentrations and biphasic effects in an intermediate concentration range, probably via the involvement of the noradrenergic system. The biphasic effect observed during application of 30 and 100 nM mesaconitine is similar to the action of noradrenaline in the rat hippocampal CA1 region. The fact that the two different kinds of actions evoked by 30 and 100 nM mesaconitine in a biphasic manner are selectively prevented by pretreatment with a- and b-adrenoceptor antagonists provides evidence that the effects involve activation of a- and b-receptors. (A15427)
来源:Toxin and Toxin Target Database (T3DB)