在１０ｍｉｎ内股动脉放血使麻醉兔ＭＡＰ下降至４０ｍｍＨｇ，然后待其自然恢复。重度失血时肾交感神经活动（ＲＳＮＡ）和心率（ＨＲ）呈现初期短暂兴奋，后期显著抑制的双相反应。延髓腹外侧头端（ＲＶＬＭ）注射ＧＡＢＡ受体拮抗剂荷包牡丹碱和阿片肽受体拮抗剂纳络酮均可逆转失血时ＲＳＮＡ和ＨＲ抑制，但不影响失血初期ＲＳＮＡ和ＨＲ增加 Femoral artery bleeding within 10min so that anesthesia rabbit MAP decreased to 40mmHg, and then to its natural recovery. Severe hemorrhagic renal sympathetic nerve activity (RSNA) and heart rate (HR) showed initial transient excitement, late significantly inhibited the biphasic response. Injection of GABA receptor antagonist bicuculline and opioid receptor antagonist naloxone both reversed the inhibition of RSNA and HR during blood loss but did not affect the increase of RSNA and HR during the early period of blood loss