Relationship between the central hypotensive effect of acupuncture or melatonin and the changes of medullary amino acid neurotransmitter

摘要

目的

研究针刺降压和褪黑素 ( Mel ) 在下丘脑前核 ( AHA ) 引起应激性高血压大鼠血压降低的作用是否与延髓头端腹外侧区 ( rVLM ) 氨基酸类递质释放的改变有关, 并分析Mel 降压机制与针刺降压机制之间的关系。

方法

采用足底电击结合噪声的方法建立应激性高血压大鼠模型; 针刺应用电针的方法, 穴位取双侧足三里; 采用中枢核团微量注射的方法给药, 观察动脉血压的改变, 同时应用脑内微透析的方法取样, 并利用高效液相色谱-荧光检测的方法, 分析透析液中氨基酸含量的改变。

结果

大鼠在接受应激处理后, 血压升高, rVLM 内谷氨酸 ( Glu ) 释放量增加, 应激性高血压大鼠在经针刺处理后, 血压回降, rVLM 内 Glu 释放量回减。微量注射 Mel 至应激性高血压大鼠的 AHA 能使血压降低, rVLM 内Glu 释放量也减少, 而 γ-氨基丁酸 ( GABA ) 和牛磺酸 ( Tau ) 释放量则增加。在 rVLM 微量注射GABAA 受体拮抗剂荷包牡丹碱 ( bicuc ) 则可部分阻断 Mel 在 AHA 引起的降压效应。

结论

针刺降压与 rVLM 内 Glu 释放量减少有关, 而 Mel 在 AHA 引起的降压效应则与 rVLM 内 Glu 释放量减少, 以及 GABA 和 Tau 释放量增加有关。针刺降压和 Mel 在 AHA 引起的降压机制都与 rVLM 内 Glu 释放量减少有关。

Abstract

Objective

To investigate whether changes of amino acid neurotransmitter releases in the rostral ventrolateral medulla (rVLM) were related to acupuncture and to the antihypertensive effect of melatonin (Mel) microinjected into the anterior hypothalamic area (AHA) of rats with stress-induced hypertension (SIH), as well as to compare and analyze the relationship between the both antihypertensive mechanisms of acupuncture and of Mel in the AHA.

Methods

Animal model of SIHR was made by electric foot shocks combined with noises. Electroacupuncture (EA) was used and “Zusanli” acupoint of both side was selected. The technique of drug microinjection into the brain was used to observe the change of blood pressure (BP), and synchronously, brain microdialysis was performed for collecting dialysate samples, and then the concentration of amino acid neurotransmitters in the dialysate samples was determined by high performance liquid chromatography combined with fluorescent detection (HPLC-FD).

Results

After the animal received stress treatment, the BP elevated, synchronously, the release of glutamate (Glu) in the rVLM increased, and when EA was performed, the elevated BP of the rats with SIH decreased, simultaneously, the release of Glu in the rVLM decreased also. After Mel was microinjected of into the AHA of the SIHR, the elevated BP attenuated, meanwhile, the release of Glu decreased, and those of γ-aminobutyric acid (GABA) and taurine (Tau) increased in the rVLM. Administration of bicuculline, an antagonist of GABA_A receptor, into the rVLM prior to microinjection of Mel into the AHA could partially block the depressor effect of Mel in the AHA.

Conclusion

The decrease in the release of Glu in the rVLM contributes to the antihypertensive effect of both acupuncture and Mel in the AHA in the rats with SIH, and the increase in the release of GABA and Tau in the rVLM is also important to Mel in the AHA.