Objective To explore the therapeutic effects of ginseng total saponins (GTSs) on cognitive impairments in astronauts caused by prolonged exposure to microgravity environment.
Methods Fifty specific pathogen-free (SPF) male Wistar rats were randomized into control, hindlimb suspension (HLS), Huperzine A (HLS-Hup A 0.1 mg/kg), low-dose GTSs (HLS-GTSs 100 mg/kg), and high-dose GTSs (HLS-GTSs 200 mg/kg) groups, based on the completion time of reward-directed conditioning tasks. Except for rats in the control group, the others were subjected to HLS and treated with drugs (day 20 – 58), received reflex test under the condition of rewarding, and underwent Nissl body staining and Western blot detection on hippocampal.
Results After modeling, rats in HLS group exhibited a reduction in the number of lever presses and an increase in the completion time of the reward-directed operant conditioning task Ⅰ (P < 0.05) when compared with the control group, which were not substantially altered in the HLS-GTSs 100 and 200 mg/kg groups (P > 0.05). In the reward-directed operant conditioning task Ⅱ, the HLS group rats demonstrated a marked decrease in the number of lever presses (P < 0.05) and nose pokes (P < 0.01) when compared with the control group rats; the HLS-GTSs 100 mg/kg showed a significant increase in the number of lever presses and nose pokes (P < 0.05), while the HLS-GTSs 200 mg/kg demonstrated a significant reduction in completion time and an elevation in the number of lever presses (P < 0.05) when compared with the HLS group rats. In visual signal discrimination task, compared with the control group rats, the HLS group rats showed decrease in the indexes of the visual signal discrimination (P < 0.01), while HLS-GTSs 100 and 200 mg/kg groups exhibited manifest increase in it (P < 0.01). In reward extinction experiment, the number of lever presses in HLS rats significantly increased when compared with the control group (P < 0.01); compared with the HLS group, HLS-GTSs 100 and 200 mg/kg groups demonstrated a marked descrease (P < 0.05). The expressions of N-methyl-D-aspartic acid receptor 1 (NR1) and phosophorylated N-methyl-D-aspartic acid receptor 2B (p-NR2B) proteins were markedly decreased in rats in the HLS group (P < 0.05 and P < 0.01, respectively), while that of NR2B protein maintained the same (P > 0.05). GTSs increased the expression levels of p-NR2B (P < 0.01).
Conclusion GTSs improved the learning and memory ability of complex operations by regulating the NR1/NR2B phosphorylation pathways in rats.
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