Neuroprotective Effect Of Clonidine On Cultured Cortical Neurons Subjected To Oxygen-glucose Deprivation And Nmda

Aims: The present study was carried out to determine the neuroprotective effect of clonidine (1, 3, 10μM) and the related mechanisms on primary cultured rat cortical neurons exposed to oxygen-glucose deprivation (OGD) and N-methyl-D-aspartate (NMDA). In addition, to observe the effect of clonidine (50, 100μg/kg) on the synaptic plasticity in normal rat hippocampal CA1 region is another aim. Methods: The 8th day of primary cultures of cortical neurons was suffered from OGD induced by depriving oxygen and glucose in the solution of incubation for 4h, while the neurons were exposed to Earle's solution in which Mg2+ is free but containing 100μM NMDA for 12h to induce another kind of injury. Clonidine (1, 3, 10μM) was added 24h before OGD or NMDA injury. Neuronal injury was detected by MTT staining method and measurement of lactate dehydrogenase (LDH) release. The effect of clonidine (50, 100μg/kg) on the synaptic plasticity in normal rat was assessed by recording the changes of LTP after that the high frequencey stimulation (HFS) was given to Schaffer. Results: 1. Effect of clonidine on primary cultured rat cortical neurons exposed to OGD in MTT staining and the release of LDH: in the group of control, the percentage of suvival rate of neurons was (100±32.12) %; and the percent of LDH release was (100±37.51) %. Compared with control, there was a significant reduction in A570 in the group of OGD (p<0.01); meanwhile, there was a notable increase in the release of LDH (p<0.01). In groups given different concentration of clonidine, the percent of survival neurons was much greater than the injured group, and the release of LDH decreased greatly as well. 2. Effect of clonidine on primary cultured rat cortical neurons exposed to NMDA in MTT staining and the release of LDH: in the group of control, the survival rate of neurons was (100±19.46) %, and the percent of LDH release was (100±18.46) %. Compared with control, there was a significant reduction in A570 in the group of NMDA (p<0.01); meanwhile, the percent of LDH release experienced a sharply growth (p<0.01). In groups given different concentration of clonidine, the percent of survival neurons was much greater than the injured group, and the release of LDH decreased greatly as well. 3. The effect of clonidine on the synaptic plasticity in normal rat hippocampal CA1 region: in vehicles, in 120min after HFS, the value of population spike (PS) sustained around (163±44.03) % of the value of baseline, which indicated that LTPs were induced successfully. In rats administered clonidine at the dosages of 50 and 100μg/kg, values of PS were significantly reduced than vehicles (p<0.01), which were (132.74±6.72) %, (118±11.01) % respectively. In adition, within 120min after HFS, the values of PS of rats administered high dose of clonidine were notably lower than that of ones given the low dosage (p<0.05). Conclusion: 1. Clonidine can exert notable neuroprotection against OGD/NMDA-induced injury in primary cultured cortical neurons. The machenism is probably though attenuating excitotoxicity which is mediated by NMDA receptor partly. 2. Clonidine can depress synaptic plasticity of hippocampal CA1 region in normal rat through the model of LTP, and this probably mediated working memory.