Inhibition of parasympathetic saliva flow by sympathetic nerve stimulation

交感神经和副交感神经都能刺激唾液腺分泌唾液，两者之间并没有相互拮抗的关系。为研究小鼠唾液腺中交感神经和副交感神经的相互作用，同时给予匹鲁卡品（一种毒蕈碱受体激动剂）和异丙肾上腺素（一种β-肾上腺素受体激动剂），与匹鲁卡品单独给药相比，唾液流量显著减少。免疫组化结果显示，水通道蛋白5（AQP 5）在毛果芸香碱刺激后定位于小鼠颌下腺和腮腺的质膜上。当匹鲁卡品和异丙肾上腺素同时给药时，在胞浆中观察到强而弥散的AQP 5标记，并且与匹鲁卡品单独给药相比，质膜和胞浆之间的染色强度差异变小。当在给予毛果芸香碱和异丙肾上腺素之前给予抑制腺苷酸环化酶的SQ 22536时，AQP 5定位的变化被恢复，并且因此唾液分泌的减少被部分恢复。结果提示异丙肾上腺素通过AC-cAMP-PKA轴抑制匹罗卡品刺激的唾液流。异丙肾上腺素刺激引起的AQP 5定位的改变可能是抑制唾液流量的机制之一。总之，交感神经刺激抑制唾液腺组织中的副交感神经系统，这一点在体内实验中得到证实。

Both sympathetic and parasympathetic nerve stimulate saliva secretion in the salivary gland, and both of them have not been thought to have mutual antagonism. The purpose of the study is to study the interaction between sympathetic and parasympathetic nerve in the mouse salivary gland.When pilocarpine (a muscarinic receptor agonist) and isoproterenol (β-adrenoceptor agonist) were given mouse at the same time, quantity of saliva flow significantly decreased compared to pilocarpine single administration. Immunohistochemistory showed that the labeling of aquaporin 5 (AQP5) was localized in the plasma membrane of the submandibular and parotid glands when the mouse was stimulated by pilocarpine. When pilocarpine and isoproterenol were administered at the same time, strong and diffuse labeling AQP5 was seen in the cytoplasm, and difference of the staining intensity between the plasma membrane and cytoplasm became small compared to the single administration of pilocarpine. When SQ22536 which inhibited adenyl cyclase was administered before administering pilocarpine and isoproterenol, the changes of the AQP5 localization was restored, and as a result decrease of salivation was restored partially. The results presented here suggest that isoproterenol suppress the pilocarpine-stimulated salivary flow via AC cAMP-PKA axis. Changes of AQP5 localization stimulated by isoproterenol possibly contributed as a mechanism in the suppression of saliva flow.In conclusion, sympathetic nerve stimulation inhibited parasympathetic nerve system in salivary gland tissue, which was demonstrated by the in vivo experiment.