安定、氟安定对刺激家兔中脑诱发升压反应的抑制作用

INHIBITORY EFFECT OF DIAZEPAM OR FLURAZEPAM ON PRESSOR RESPONSE INDUCED BY THE STIMULATION OF MIDBRAIN IN THE RABBIT

32只家兔,用α-氯醛糖和氨基甲酸乙酯麻醉,肌肉麻痹行人工呼吸。观察安定或氟安定对刺激中脑导水管周围灰质背侧部(dPAG)所引起升压反应的影响。当静脉注射安定或氟安定注入侧脑室,使刺激中脑诱发的升压反应受抑,表现为收缩压增量(ΔSBP)和平均压增量(ΔMBP)减小。微量注射氟安定到双侧延髓腹外侧头端区(rVLM),也出现升压反应受到抑制,降低ΔSBP和ΔMBP;而于双侧腹外侧尾端区(cVLM)微量注射相同剂量氟安定则无抑制作用。在rVLM用GABA_A受体阻断剂荷包牡丹碱预处理,可阻断氟安定对升压反应的抑制作用。 结果表明:安定、氟安定可抑制刺激中脑诱发的升压反应,这作用可能是通过激活rVLM处GABA_A受体而实现的。

Experiments were performed on 32 rabbits anaesthetized with α-chloralose and ure-thane, paralyzed with flaxidil and artificially ventilated. The pressor response was elicit-ed by stimulation of dorsal part of midbrain periaqueductal gray (dPAG). Intravenousinjection of diazepam (2 mg/kg) or intracerebroventricular application of flurazepam(2 mg/50 μl) resulted in attenuation of the pressor response induced by the stimulationof midbrain. Bilateral microinjection of flurazepam (100 μg in 0.25 μl) into rostralventrolateral medulla (rVLM) depressed the pressor response to midbrain stimulation.Microinjection of flurazepam of the same dosage into caudal ventrolateral medulla(cVLM), however, had no depressant effect. Pretreatment with bicuculline in rVLMprevented the inhibitory effect of flurazepam on the pressor response. These results men-tioned above suggest that diazepam or flurazepam inhibits the pressor response evokedby midbrain stimulation, and the effect may be mediated by the activation of theGABA_A receptor in rVLM.