延髓头端腹外侧区调节心血管活动的γ-氨基丁酸机制

γ-aminobutyric Acid Receptor-Mediated Mechanisms in Regulation of Cardiovascular Activities in the Rostral Ventrolateral Medulla of Rats

目的：探讨延回头端腹外侧区（RVLM）调节心血管活动的γ-氨基丁酸（GABA）机制。方法：采用3管玻璃微电线作SD大鼠脑内微量注射，观察在RVLM微量注射GABA受体阻断剂后，对心血管活动的紧张性抑制作用的影响。结果：双侧RVLM微量注射GABA_A受体阻断剂4mmol／L荷包牡丹硷20nl（一侧总量80pmol）后，平均动脉压（MAP）升高8．66±0．36kPa（P＜0．01），心率（HR）加快45．3±4．9次／min（P＜0．05）；双侧RVLM微量注射GABA_B受体阻断剂2－OH－S也出现升压及心率加快效应。低剂量组（一侧2－OH－S总量400nmol），MAP升高2．70±0．24kPa（P＜0．01），HR加快16．0±2．1次／min（P＜0．01）。高剂量组（一侧2－OH－S总量1nmol）MAP升高3．01±0．19kPa（P＜0．01），HR加快17．3±1．8次／min（P＜0．05）。结论：RVLM的GABA紧张性抑制作用可通过GABA_A和GABA_B两种受体中介。

ObjectiveTo find out the receptor-mediated mechanism of γ-aminobutyric acid (GABA) in regulation of cardiovascular activities in the rostral ventrolateral medulla (RVLM) of rats. Methods: Experiments werePerformed on male SD rats, which were anesthetized with urethane and allowed to have spontaneous breath. Westudied their blnd pressure and heart rate response to administration of GABA_A and GABAB antagonist intoRVLM by multibarreled micropipette. Results: Bilateral microinjection of GABA_A antagonist 4 mmol/L bicucuiline 20 nl into RVLM induced significant increase in mean arterial pressure(MAP) and heart rate (HR), average increases were 8. 66±0. 36 kpa (P<0. 01 ) and 45. 3±4. 9 beats / min (P<0. 05) respectively. Bila teral microinjection of GABAS antagonist 2-hydroxy-saclofen (2-OH-S) into RVLM also induced significant increases in MAP and HR. In low dose group (20 mmol/L of 20 nl, total 400 pmol/side), MAP and HR increaseswere 2. 70±0. 24 kpa (P<0. 01) and 16. 0±2. 1 beats/min (P<0. 01) respectively. In high dose group (25mmol/L of 40 nl, total 1 nmol/side), MAP and HR increases were 3. 01± 0. 19 kpa and 17. 3± 1. 8 beats/min,respectively. Conclusion: Both GABA_B and GABA_B receptors are involved tonic inhibition mechanisms in regulation of cardiovascular activities in the RVLM.