Scorpion envenomation is a public health problem in tropical and subtropical areas. In Brazil, Tityus serrulatus is the biggest cause of accidents with venomous animals. Tityus serrulatus venom causes symptoms related to a great activation of the autonomic system attributed to a massive release of sympathetic and parasympathetic mediators. This effect is attributed to the presence of toxins acting in Na+ and K+ ion channels, leading to an increase in cell excitability. Although gastrointestinal symptoms, like diarrhoea and sialorrhea, is observed in moderate to severe cases, little attention is given in clinical reports. Gastrointestinal motility is controlled by the enteric nervous system which is composed of a wide variety of interconnected neurons that are influenced by the sympathetic and parasympathetic nervous systems. Thus, this work aimed to characterize the effects of Tityus serrulatus venom on sympathetic and parasympathetic neurotransmission of rat jejunum, as well as to investigate possibles effects on other neurons of the enteric nervous system. To this, we verify the effects of Tityus serrulatus venom on the contractility of isolated rat jejunum through organ-bath experiments. We observed that venom can induce both contraction and relaxation. The contraction was partially inhibited by atropine (1 μM) and by suramin (0.1 mM) through tetrodotoxin-resistant and sensitive mechanisms. The relaxation was completely inhibited by 3 μM propranolol and partially inhibited by 1 μM phentolamine. Suramin induced a slowing of relaxation curve. Tetrodotoxin completely inhibits the relaxation induced by Tityus serrulatus venom, but the contraction curves were only partially reduced in their initial portion. The final part of the curve was largely enhanced by Tetrodotoxin. Atropine blocks almost completely the contraction curve in the presence of Tetrodotoxin. These results indicate that Tityus serrulatus venom induces the release of both excitatory (predominantly acetylcholine) and inhibitory (mainly noradrenaline) neurotransmitters. The effects of Tityus serrulatus venom on organ contractility was quite complex and seem to derive from a diffuse and nonspecific release of mediators from autonomic and enteric nervous systems. Further investigation of venom action and its isolated toxins can reveal important aspects to deepen our knowledge about the enteric nervous system transmission and the interaction between excitatory and inhibitory mediators as well as the physiological role of Na+ and K+ ion channels in gut motility.

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Tityus serrulatus 蝎毒对离体空肠的影响：研究肠神经系统神经元之间相互作用的非常有用的工具

蝎毒是热带和亚热带地区的一个公共卫生问题。在巴西，Tityus serrulatus 是导致有毒动物事故的最大原因。Tityus serrulatus 毒液引起的症状与自主神经系统的极大激活有关，这归因于交感神经和副交感神经介质的大量释放。这种效应归因于作用于 Na+ 和 K+ 离子通道的毒素的存在，导致细胞兴奋性增加。虽然在中度至重度病例中观察到胃肠道症状，如腹泻和流涎，但在临床报告中很少关注。胃肠动力受肠神经系统控制，肠神经系统由受交感神经和副交感神经系统影响的各种相互连接的神经元组成。因此，这项工作旨在表征 Tityus serrulatus 毒液对大鼠空肠交感神经和副交感神经传递的影响，并研究对肠神经系统其他神经元的可能影响。为此，我们通过器官浴实验验证了锯齿鲟毒液对离体大鼠空肠收缩力的影响。我们观察到毒液可以引起收缩和放松。阿托品 (1 μM) 和苏拉明 (0.1 mM) 通过抗河豚毒素和敏感机制部分抑制了收缩。3 μM 心得安完全抑制松弛，1 μM 酚妥拉明部分抑制。苏拉明引起弛豫曲线减慢。河豚毒素完全抑制了虎尾鱼毒液引起的松弛，但收缩曲线在其初始部分仅部分减少。河豚毒素大大增强了曲线的最后一部分。在河豚毒素存在的情况下，阿托品几乎完全阻断收缩曲线。这些结果表明 Tityus serrulatus 毒液诱导兴奋性（主要是乙酰胆碱）和抑制性（主要是去甲肾上腺素）神经递质的释放。Tityus serrulatus 毒液对器官收缩力的影响非常复杂，似乎源于自主神经和肠神经系统介质的弥散和非特异性释放。