延髓腹外侧部头端在重度失血兔肾交感神经活动抑制和心率减慢中作用

在戊巴比妥钠麻醉兔中,记录股动脉血压,心率(HR)和肾交感神经活动(RSNA)。在10分钟内股动脉放血使平均动脉压(MAP)下降至5.3 kPa,停止放血后让其自然恢复。重度失血过程中RSNA和HR呈现先兴奋后抑制的双相反应。迷走神经切断和静脉注射纳洛酮可翻转重度失血时RSNA的抑制,却不能阻断重度失血时HR的降低。延髓腹外侧头端(RVLM)注射γ一氨基丁酸(GABA)拮抗剂荷包牡丹碱和阿片肽拮抗剂纳洛酮均可翻转重度失血引起的RSNA抑制和HR下降。失血初期RSNA增强和心率(HR)增加不受迷走神经切断、静脉和RVLM注射纳洛酮和RVLM注射荷包牡丹碱的影响。这些结果表明RVLM中的阿片肽和GABA参与重度失血引起的RSNA抑制和HR下降,但与失血初期的RSNA和HR的升高无关。

THE ROLE OF ROSTRAL VENTROLATERAL MEDULLA IN THE INHIBITION OF RENAL SYMPATHETIC NERVE ACIVITY AND THE DECREASE IN HEART RATE DURING SEVERE HEMORRHAGE IN RABBITS

The femoral arterial pressure, heart rate (HR) and renal sympathetic nerve activity (RSNA) were recorded in pentobarbital anesthetized rabbits. Animals were bled to a mean arterial pressure (MAP) of 5.3 kPa within 10 minutes, and then recovered naturally. RSNA and HR showed biphasic responses with initial excitation and later inhibition. Vag-otomy and intravenous injection of naloxone reversed the inhibition of RSNA, but did not abolish the decrease in HR during severe hemorrhage. Microinjection of both GABA antagonist bicuculline and opiate antagonist naloxone into the rostral ventrolateral medulla (RVLM) reversed the inhibition of RSNA and the decrease in HR induced by severe hemorrhage. The initial increase in RSNA and HR were not influenced by vagotomy,intraven-ous injection of naloxone, microinjection of naloxone and bicuculline into RVLM. These results indicate that the opiate and GABA in RVLM may contribute to the inhibition of RSNA and the decrease in HR induced by severe hemorrhage, but do not relate to the initial increase in RSNA and HR at an early stage of hemorrhage.