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OBJECTIVE Microgravity exerts several negative effects on the learning and memory of astro-nauts during space flight.Rg1 and Rb1,the key steroidal components of ginseng,have shown potent neuroprotec-tive effects with a high safety profile.The object of the current study is to investigate the influence of Rg1 and Rb1 on simulated microgravity-induced memory and learning dysfunction in the hindlimb suspension(HLS)rat model.METHODS The HLS rats were orally administered Rg1(30 and 60 μmol·kg-1)or Rb1(30 and 60 μmol·kg-1)for four weeks.The Morris water maze test(MWM)and reward operating conditioning reflex test(ROCR)were conducted to evaluate spatial and associative learning and memory.After the behavior tests,the serum and the prefrontal cortex(PFC)were dissected to measure the mechanism.RESULTS Rg1 and Rb1 treatment amelio-rated the cognitive deficits of HLS-exposure rats in MWM and ROCR,reduced reactive oxygen species generation and increased antioxidant enzyme activity.Rg1 and Rb1 also assisted in the recovery of mitochondrial complex Ⅰ(NADH dehydrogenase)activities and Mfn2,and decrea-sed Drp-1 expression.Furthermore,Rg1 and Rb1 reduced the ratio of Bax/Bcl-2 and the expression of cleaved-cas-pase 3,cytochrome c,increased the levels of SYN,PSD95 and activated BDNF-TrkB/PI3K-Akt pathway in the PFC.CONCLUSION Rg1 and Rb1 treatment attenuated cog-nitive deficits induced by HLS,mitigated mitochondrial dysfunction,attenuated oxidative stress,inhibited apopto-sis,and increased the synaptic plasticity,which was partly mediated by the modulation of the BDNF-TrkB/PI3K-Akt signaling.
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Objective To observe the effect of IcarisideⅡ (ICSⅡ) on spatial learning and memory impairments and axonal regeneration induced by chronic cerebral hypoperfusion (CCH) in rats.Methods 90 male SD rats were randomly divided into normal group,sham operation group,CCH group and ICS Ⅱ low,middle and high-dose treatment groups.The chronic cerebral hypoperfusion model was established by permanent bilateral common carotid artery occlusion.Then these rats in ICS Ⅱ low,middle and high-dose treatment groups were given ICS Ⅱ4,8 and 16 mg/(kg · d) by gavage on the 1st day after modeling.There were 5 rats in every group at each observing time(4,8 and 12 week).Morris water maze experiment was utilized to assess the escape latency and the target quadrant residence time while HE and immunohistochemistry analysis were applied to test the morphology change and expressions of GAP-43,MAP-2 and Nogo-A in hippocampal CA 1.Results Compared with those of sham operation groups at 4,8 and 12 week respectively,the escape latency in CCH group were significantly prolonged(40.02±4.95) s,(42.29±5.75) s,(53.68±6.14) s vs (26.43±2.68) s,(26.84±2.06) s,(31.53±4.12) s,P＜0.05;the target quadrant residence time were significantly reduced(28.53±2.40) s,(28.02±4.28) s,(22.60±4.03) s vs (33.34±2.89) s,(33.31 ±4.14) s,(31.63±2.20)s,P＜0.05);the expressions of GAP-43 and Nogo-A were increased with that of MAP-2 reduced(P＜0.05).Meanwhile,the neuropathological changes with more denatured neurons and less normal neurons were found in hippocampal CA1.However,compared with those of CCH group,the escape latency of ICS Ⅱ middle and high-dose groups (30.58±3.03) s,(29.19±4.23) s,(38.77±5.80) s;(28.90±2.98) s,(26.91 ±6.63) s,(36.51 ±3.98) s) were shortened (P＜0.05);the target quadrant residence time (32.54± 3.41) s,(32.69±3.47) s,(28.27±3.57) s;(32.69±3.54) s,(33.20±4.29) s,(28.07±4.04) s) were increased (P＜ 0.05);the expression of Nogo-A was decreased while those of GAP-43 and MAP-2 were conversely increased (P＜0.05).Moreover,few denatured neurons were observed in hippocampal CA1.But there were no differences for those indexs between CCH group and ICS Ⅱ low-dose treatment groups (P＞0.05).Compared with those in 8 week and 4 week,the escape latency and the target quadrant residence time were prolonged and reduced with the expression of Nogo-A increased in all groups except normal group and sham operation group(P＜0.05),the expressions of GAP-43 and MAP-2 were decreased in CCH group and ICS Ⅱ low-dose treatment group(P＜0.05),but there were no significant differences in ICS Ⅱ middle and high-dose treatment groups at 12 week(P＞0.05).However,there were no statistical significance of all indexes between 8 week and 4 week(P＞0.05).Conclusion ICS Ⅱ can improve the spatial learning and memory in chronic cerebral hypoperfusion rats,which may be achieved by neuroprotective effects and reducing the expression of Nogo-A consequently promotes the regeneration of axons.