[Assessment of neuroprotective effects of polyprenols in a rat model of a vital psychogenic stress

The purpose of investigation was to assess protective action of polyprenols (2 and 10 mg/kg) in a rat model of posttraumatic stress disorder (PTSR). PTSR was reproduced in situation of unavoidable vital stress in rats by placing them into a cage with a hungry piton. For the first five minutes the piton was separated from the rats with transparent wall to get acquainted each other with a situation. Then, the wall was elevated, and piton attacked a rat in the presence of other rats (22 animals). The majority of rats shrank into a corner paralysed with terror. The other rats behaved differently. Some of them attacked the piton, bited it, but the majority raced chaotically in the cage with piton. The exposure of rats with piton was 20 minutes. Over that time it strangled and swallowed 1 or 2 rats. Polyprenols (from 8 to 18 isoprene units) were injected i.p. in doses of 2 or 10 mg/kg in oil solution for 7 days beginning from the 1st day of the experiment (the first injection was 1 h after psychogenic exposure). The behavioral reactions were assessed in open field, elevated plus maze, in Porsolt's test and in one trial passive avoidance response. The effects of polyprenols 2 and 10 mg/kg were different. Polyprenols 2 mg/kg did not change horizontal and vertical motor activity in rats, moderately (1.5 times) decreasing explorative activity and increasing grooming in open field. Emotional reactions were not changed. In the elevated plus maze, polyprenols 2 mg/kg had showed moderate anxiolytic activity manifested as 2.5-fold elevation of hangings number. In Porsolt's test for depression, polyprenols 2 mg/kg moderately increased time of active swimming and sharply decreased time of immobilization (down to zero), suggesting antidepressant properties of this dose (2 mg/kg) of polyprenols. In passive avoidance test, psychogenic stress facilitated formation and storage of skills (only 10 % of rats entered the dark chamber 24 h after formation of the skill compared with 60 % of naive rats). Polyprenols 10 mg/kg moderately activated explorative behavior and emotional response without any effect on motor activity. In the elevated plus maze, the effects of polyprenols 2 and 10 mg/kg were similar in general. In Porsolt's test, polyprenols 10 mg/kg had no significant antidepressant effect. At last, in passive avoidance test, 30 % of rats have not trained after psychogenic stress, and the trained rats reproduced the passive avoidance response with phenomenon of hypermnesia, as in control group. So, polyprenols 2 and 10 mg/kg possess anxiolytic and antidepressant activity in a rat PTSD model. Polyprenols 2 mg/kg are more effective than polyprenols 10 mg/kg.

polyprenols, central effects, behavior, passive avoidance, posttraumatic stress disorder, neuroprotection, medicine of catastrophes

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