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的唾液分泌，但两者并不是相互拮抗的。本研究的目的是研究小鼠唾液腺交感神经和副交感神经之间的相互作用。当同时给予M受体激动剂匹罗卡品和β受体激动剂异丙肾上腺素时，与匹罗卡品单独给药相比，唾液流量显著减少。免疫组织化学结果显示，在毛果芸香碱刺激下，水通道蛋白5(AQP5)标记定位于小鼠颌下腺和腮腺的质膜。当毛果芸香碱和异丙肾上腺素同时作用时，AQP5在细胞质内可见强而弥漫的标记，与单独给药相比，质膜和细胞质的染色强度差异较小。在给予匹罗卡品和异丙肾上腺素前给予抑制腺苷环化酶的SQ22536，可恢复AQP5定位的变化，从而部分恢复唾液分泌的减少。上述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动。异丙肾上腺素刺激AQP5定位的改变可能是其抑制唾液流动的机制之一。结论：交感神经刺激抑制了唾液腺组织中的副交感神经系统，体内实验证实了这一点。

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.