PACAP对老年大鼠脑缺血再灌注神经元损伤及M受体的影响

目的　观察垂体腺苷环化酶激活肽 (PACAP)对老年大鼠全脑缺血再灌注模型神经元损伤和M受体 (mAChR)的影响。方法　利用四血管结扎法 (4 VO)建立老年大鼠全脑缺血再灌注复合伤模型 ,侧脑室注射PACAP38(5 0nmol·kg-1 ) ,用HE染色和TUNEL标记法计数皮层和海马CA1区正常神经元和凋亡神经元数目 ,采用放射性配体结合实验和饱和结合实验检测皮层和海马mAChR的3 H QNB特异结合量和结合参数。结果　脑缺血再灌注d 3后 ,皮层和海马CA1区正常神经元数显著减少、凋亡神经元数显著增加 (P<0 0 1 ) ,海马 (P <0 0 1 )和皮层 (P <0 0 5 ) 3 H QNB的特异结合量减低 ,最大结合容量 (Bmax)显著下降 (P <0 0 1 ) ,但亲和力 (Kd)不变。PACAP组皮层和海马CA1区缺血损伤神经元和凋亡神经元数目均比模型组明显降低 (P <0 0 5 ) ,3 H QNB的特异结合量和Bmax提高 (P <0 0 5 ) ,Kd 值不变。结论　脑缺血再灌注所致神经元损伤、凋亡和缺失可能是导致mAChR活性降低、密度下降的主要原因。PACAP具有抗脑缺血所致神经元损伤、保护中枢胆碱能系统的作用 ,在缺血性脑血管病防治中有潜在应用价值

Effects of PACAP on neuronal damage and muscarinic receptor after global ischemia-reperfusion in old rat

AIM To explore the effect of pituitary adenylate cyclase activating polypeptide (PACAP) on neuronal damage and muscarinic cholinergic receptor (mAChR) after global ischemia reperfusion injury in old rats. METHEDS Global ischemia reperfusion injury was created by the four vessel occlusion (4 VO) method. PACAP38 (50 nmol·kg -1 ) was infused into lateral ventricle preceding the occlution. The number of normal neurons and apoptotic neurons stained by HE and TUNEL were counted 3 days after reperfusion in cerebral cortex and hippocampal CA1 subfield. We also determined the binding parameters of 3H quinuclidinyl benzilate ( 3H QNB) in cerebral cortex and hippocampus. RESULTS The number of apoptotic and damaged neurons increased remarkably ( P <0 01), whereas 3H QNB specific binding significantly decreased both in cortex ( P <0 05) and hippocampus ( P <0 01) in ischemic rats than those in sham group 3 days after reperfusion( P <0 05), PACAP reduced the number of apoptotic neurons and increased 3H QNB specific binding ( P <0 05). Saturation experiment indicated that the maximum density (B max ) of muscarinic cholinergic receptor in cortex and hippocampus was significantly lower in ischemic reperfusion group compared with that in sham operated group ( P <0 01), PACAP treatment prevented the B max decrease ( P <0 05). The binding affinity (dissociation constant, K d) showed no differences in the three groups. CONCLUTION The present study provides further evidence for the neuroprotective effects of PACAP, and implies that it might be a promising preventive therapeutic agent in ameliorating ischemic brain damage.