The Investigation Of The Regulatory Effects And Underlying Molecule-mechanism Of The Alpha2-adrenergic Agonistsclonidine On The Learning And Memory In Rats With Cerebral Ischemiavia The NMDAR2B Receptors Pathway

Objective To investigate the regulatory effects and underlying molecule-mechanism of the alpha 2-adrenergic agonists clonidine on learning and memory in rats with cerebral ischemia via the NMDAR2 B receptors pathway.Methods The cerebral ischemia rat model was established by ligation of the middle cerebral arteries. The Sprague Dawley rats were randomly divided into the sham-operative group, the cerebral ischemia model group, the clonidine(40 μg·kg-1·d) normal group, the clonidine(40 μg·kg-1·d) ischemia group, the yohimbine(5 mg·kg-1·d) + clonidine(40μg·kg-1·d) group, ifenprodil(5 mg·kg-1) + clonidine(40 μg·kg-1·d) group, PD184352(2 mg·kg-1·d)+ clonidine(40 μg·kg-1·d) group, piracetam(600 mg·kg- 1·d) group.Drug was administrated by i.p. for 7 days in treated group and once again on the day of surgery. The cerebral ischemia rat model was made by right middle cerebral artery occlusion for 2 h and reperfusion for 28 days. The learning and memory ability of rats with cerebral ischemia assayed by Morris water maze. Expressions of NMDAR2B/phosphor-NMDAR2 B, ERK2/phosphor-ERK2, CREB/phosphor-CREB, NF-κB/phosphor-NF-κB protein levels were assayed by western blotting.Results(1) The Morris water maze results showed that the learning and memory ability is obviously impaired in cerebral ischemia rats(P ﹤ 0.01), but clonidine can improve the learning and memory ability of rats with cerebral ischemia(P<0.05). It show no significant improvement on the ability of learning and memory(P >0.05) in the the yohimbine(5 mg·kg-1·d) + clonidine(40 μg·kg-1·d) group, ifenprodil(5 mg·kg-1·d)+ clonidine(40 μg·kg-1·d) group, PD184352(2 mg·kg-1·d) + clonidine(40 μg·kg-1·d) group.(2) Western blot results show that compared with the sham-operative group, the expression of NR2 B and Phospho-NMDAR2 B in hippocampus were decreased in ischemia group(P<0.05), but clonidine can up-regulate these proteins(P<0.05); Compared with the sham-operative group, the expression of ERK2, Phospho-ERK2, CREB, Phospho-CREB in hippocampus were increased in the ischemia group(P<0.05), but the clonidine can down-regulate these proteins(P<0.05).(3) Western blot results show that compared with the sham-operative group, the expression of Phospho-NF-κB in hippocampus were increased in ischemia group(P<0.05), but clonidine can down-regulate it(P<0.05).(4)Compared with the sham-operative group, the expression of NR2 B in cortex were no significant difference in the ischemia group, and clonidine do not affect the expression ofNR2B(P>0.05).Conclusion Alpha 2-adrenergic agonists clonidine can improve the learning and memory ability of rats with cerebral ischemia, and NMDAR2 B, ERK2, CREB, NF-κB were involved in this effect.