一氧化氮合酶抑制剂L-NAME对大鼠脑缺血耐受诱导的影响

Effect of nitric oxide synthase inhibitor L-NAME on the induction of brain ischemic tolerance in rats

采用大鼠四血管闭塞全脑缺血耐受模型和脑组织切片形态学方法 ,观察应用一氧化氮合酶 (NOS)抑制剂L NAME对大鼠海马CA1区脑缺血耐受 (BIT)诱导的影响 ,在整体水平探讨一氧化氮 (NO)在BIT诱导中的作用。 5 4只Wistar大鼠凝闭双侧椎动脉后分为 6组 :( 1)假手术组 (n =6) :分离双侧颈总动脉 ,但不阻断脑血流 ;( 2 )损伤性缺血组 (n =6) :全脑缺血 10min ;( 3 )预缺血 +损伤性缺血组 (n =6) :脑缺血预处理 (CIP) 3min ,再灌注 72h后行全脑缺血 10min ;( 4)L NAME组 :分别于CIP前 1h和后 1、12及 3 6h腹腔注射L NAME ( 5mg/kg) ,每个时间点 6只动物 ,其余步骤同预缺血 +损伤性缺血组 ;( 5 )L NAME +L 精氨酸组 (n =6) :于CIP前 1h腹腔注射L NAME ( 5mg/kg)和L 精氨酸 ( 3 0 0mg/kg) ,其它步骤同L NAME组 ;( 6)L NAME +损伤性缺血组 (n =6) :于腹腔注射L NAME ( 5mg/kg) 72h后行全脑缺血 10min。实验结果表明 ,( 1)单纯 10min全脑缺血可使海马CA1区组织学分级增加 (表明损伤加重 ) ,神经元密度降低 (P <0 0 1) ;( 2 )预缺血 +损伤性缺血组的海马CA1区组织学分级、神经元密度与假手术组相比 ,无显著性差别 (P >0 0 5 ) ;( 3 )L NAME组中 ,应用L NAME后海马CA1区组织学分级增加 ,神经元密度降低 ,与预缺血

To explore the role of NO in the induction of brain ischemic tolerance (BIT) in vivo, the effect of nitric oxide synthase (NOS) inhibitor L-NAME on the induction of BIT induced by cerebral ischemic preconditioning (CIP) was investigated in the hippocampal CA1 subfield in CIP and ischemic insult models established by rat four-vessel occlusion using brain tissue section and thionine staining methods. Fifty-four male Wistar rats were divided into 6 groups: (1) sham-operated group (n=6): bilateral common arteries were separated without occluding the cerebral blood flow; (2) ischemia group (n=6): an ischemic insult for 10 min was given; (3) CIP+ischemia group (n=6): 3-min CIP was preformed 72 h prior to 10-min ischemic insult; (4) L-NAME group (total n=24, n=6 for each subgroup): L-NAME (5 mg/kg, i p ) was administered 1 h prior to CIP and 1, 12 and 36 h after CIP, respectively. Other procedures were the same as those for the CIP+ischemia group; (5) L-NAME+L-Arg group (n=6): L-NAME (5 mg/kg, i p ) and L-Arg (300 mg/kg, i p ) were administered 1 h prior to CIP, other procedures were the same as those for the L-NAME group; (6) L-NAME+ischemia group (n=6): L-NAME (5 mg/kg, i p ) was administered 72 h before the 10-min ischemic insult. The results showed that (1)10-min ischemic insult resulted in an increase in the histological grade (indicating a more serious tissue injury) and a decrease in pyramidal neuronal density (P<0 01); (2) the histological grade and neuronal density in hippocampal CA1 in the CIP+ischemia group were similar to those in the sham-operated group (P>0 05); (3) in the L-NAME group, administration of L-NAME brought about an increase in the histological grade and a decrease in neuronal density (P<0 01), suggesting that L-NAME blocked the protection of CIP; (4) the neuronal damage in L-NAME+L-Arg group was slighter than that in the L-NAME group, but still more serious than that in the CIP+ischemia group, suggesting that L-Arg partly reversed the blocking effect of L-NAME; (5) the morphological representations in L-NAME+ischemia group were basically similar to those in the ischemia group. The results mentioned above indicate that NO is involved in the induction of BIT in vivo. The blocking effect of L-NAME administered at 36 h after CIP was obviously weaker than the effects of L-NAME administered 1 h prior to CIP, and 1 or 12 h after CIP. It is suggested that NO is involved in the induction of BIT at an early stage and that the involvement might take place via activating cascades of the events.