延髓—脊髓P物质能神经元下行通路参与毒扁豆碱的中枢升压反应

大鼠延髓腹侧面头端应用毒扁豆碱引起血压升高和心率加快,伴有延髓腹侧面头端胆碱酯酶活性降低和脊髓蛛网膜下腔灌流液中P物质样免疫反应活性升高。在延髓腹侧面头端应用阿托品或脊髓蛛网膜下腔注射P物质拮抗剂D-脯~2,D-苯丙~7,D-色~9-P物质均可阻断毒扁豆碱的心血管效应。脊髓蛛网膜下腔注射P物质抗血清或辣椒素均可减弱毒扁豆碱的升压反应。实验结果提示,毒扁豆碱作用于延髓腹侧面头端的M受体,兴奋了延髓-脊髓P物质能神经元下行通路,使之释放P物质,引起交感肾上腺髓质系统兴奋,从而使血压升高和心率加快。

Descending Bulbospinal Substance-P-containing Pathway Involved in Pressor Response Evoked by Physostigmine

The mechanisms of pressor response elicited by application of physos-tigmine (PHY) on rostral ventral surface of the medulla oblongata (RVM) were investigated in Wistar rats. Application of PHY to RVM induced an increases in mean arterial pressure (MAP) and heart rate (HR), accompanied with decrease in acetylcholinesterase activity in RVM and increase in. substance-P-like immunoreactivity (SPLI) in spinal cord superfusion samples. The pressor response was blocked completely by either pre-applic-ation of muscarinic antagonist atropine to RVM or intrathecal pre-injec-tion of substance P antagonist D- pro2 , D-phe7 , D-trp9-substance P. Intrathecal injection of substance P antiserum inhibited the pressor response to PHY by more than 40% as compared to control. Capsaicin had similar effects. These findings suggest that PHY indirectly excited the muscarinic receptor in RVM and caused a release of substance P from the spinal cord concomi tant with an increases in MAP and HR.