下丘脑室旁核内GABA在中枢高渗刺激诱发的心血管反应中的作用

目的：探讨下丘脑室旁核（PVN）内的γ-氨基丁酸（GABA）在中枢高渗刺激诱发的应激性心血管反应中的作用及其机制。方法：在清醒自由活动大鼠,用脑部微量透析法和高效液相色谱法观察中枢高渗刺激对PVN区域GABA含量的影响,并同时记录血压和心率的变化;用GABAA受体阻断剂Bicuculline或GABAB受体阻断剂Saelofen直接灌流PVN区并给予中枢高渗刺激,进一步探讨PVN区GABA在中枢高渗刺激诱发的应激性心血管反应中的作用。结果：①PVN局部灌流0．6mol／L盐水时,血压和心率都显著增加（均为P〈0．01）,同时,PVN区细胞外液中GABA水平也明显增加到刺激前的561．96％±173．96％（P〈0．05）;②PVN局部灌流Bicuculline或Saclofen的同时,给予0．6mol／L盐水的刺激,可使高渗刺激引起的血压增加幅度明显降低（均为P〈0．01）,而心率的增加幅度未受明显影响（均为P〈0．05）。结论：中枢高渗刺激可引起PVN内GABA的分泌,而后者可通过GABAA和GABAB受体产生血压的升高反应。

Cardiovascular change induced by central hypertonic saline are accompanied by GABA release in awake rats

Aim： To investigate the possible involvement of 7-aminobutyric acid（GABA） in the paraventricular nucleus（PVN） in cardiovascular responses induced by central salt loading. Methods： Direct perfnsion into PVN region with hypertonie saline（0.6 mol/L） was performed in conscious rats by using an in vivo brain microdialysis technique. Then, the extracellular concentration of GABA in the PVN region was measured by microdialysis and high performance liquid chromatography（HPLC） techniques, and the blood pressure（BP） and heart rate （HR） were recorded simultaneously. Bicuculline（an antagonist of GABAA receptor） or saclofen（an antagonist of GABAB receptor） were coperfused with hypertonic saline into PVN region, then the cardiovascular responses were examined. Results： ①The local perfnsion of 0.6 mol/L saline elicited significant increases on BP and HR（ P 〈 0.01 ）. In addition, perfnsion of 0.6 mol/L saline increased the extracellular GABA levels in the PVN region, which reached 561.96 % ± 173.96 % （ P 〈 0.05） of the basal level. ②Bicuculline or salcofen significantly attenuated the increased response of BP（ P 〈 0.01, respectively）, whereas the antagonists did not influence the response of HR induced by hypertonic saline. Conclusion： Local perfnsion of hypertonic saline in the PVN region elicits a local release of GABA, which may act via GABAA and GABAs receptors to produce pressor response.