γ-氨基丁酸在下丘脑室旁核的心血管效应及其机制分析

Cardiovascular Effect and Its Mechanism of γ-Aminobutyric Acid in the Hypothalamic Paraventricular Nucleus

实验在66只乌拉坦麻醉、箭毒制动、人工呼吸的Wistar大鼠上进行。单侧室套核（PVN）内注入γ－氨基丁酸（GABA）引起平均动脉压（MAP）降低、心率（HR）减慢，该效应可为PVN内预注入GABA受体阻断剂荷包牡丹碱所阻断；单侧PVN内注入荷包牡丹减引起MAP升高，HR增快，该效应可为PVN内注入α1受体阻断剂哌唑嗪或α2受体阻断剂有亨宾所阻断或显著减弱。上述结果表明，GA－BA在PVN有降压和减慢心率的效应，此效应是通过激活PVN内的GABA受体而实现的；PVN的内源性GABA具有紧张性降压和减慢心率的作用，此作用可能是通过抑制PVN内去甲肾上腺素递质系统的紧张性升压和加快心率效应而实现的。

Experiments were performed on 66 urethane-anesthetized, tubocurarine-paralyzed and artifi-cially ventilated rats. Microinjection of γ-aminobutyric acid (GABA) into the unilateral hypothalamic paraven-tricular nucleus (PVN) induced a decrease in mean arterial pressure and heart rate. The effect of GABA could be blocked by preinjection of GABA receptor antagonist bicuculline into the PVN. Microinjection of bicu-culline into the unilateral PVN induced an increase in mean arterial pressure and heart rate. The effect of bicuculline could be blocked or significantly attenuated by preinjection of α1-receptor blocker prazosin or α2-re-ceptor blocker yohimbine into the PVN. The results indicate that GABA has depressor and bradycardia effects through the activation of GABA receptor in the PVN,and endogenous GABA in the PVN has tonic depressor and bradycardia effects which may be mediated by inhibiting the pressor and tachycardia effects of nora-drenaline transmitter system.