Analysis of neuroprotective effects of polyprenols in a rat model of posttraumatic stress disorder

Abstract

The purpose of investigation was to assess protective action of polyprenols (2 and 10 mg/kg) in a rat model of posttraumatic stress disorder (PTSD). PTSD was reproduced in situation of unavoidable vital stress in rats by replacing them into a cell with hungry piton. For the five first 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 seized a rat, asphyxied it when other rats (22) observed at the situation. The majority of rats were collected in the corner dying away from the beast. The other rats behaved themselves differently. Some of them attacked the piton, bited it, but the majority raced chaotically on the cell with piton. The exposure of rats with piton was 20 minutes. For that time it seized and asphyxied 1 or 2 rats. Polyprenols (from 8 till 18 isoprene units) were injected i. p. in doses of 2 or 10 mg/kg in oil solution for 7 days beginning with 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 of 2 and 10 mg/kg were different. Polyprenols 2 mg/kg did not change horizontal and vertical motor activity in rats, moderately (in 1.5-fold) decreasing explorative activity and increasing grooming in open field. Emotional reactions were not changed. In the elevated plus maze, polyprenols 2 mg/kg possessed mild anxiolytic activity performed in 2.5-fold elevation of hangings number. In Porsolt’s test on depression, polyprenols 2 mg/kg moderately increased time of active swimming and sharply decreased time of immobilization (up to zero). That indicated on antidepressant properties of this dose (2 mg/kg) of polyprenols. In passive avoidance test, psychogenic stress facilitated formation and storage of habit (only 10 % of rats entered the dark chamber in 24 h after formation of the habit compared with 60 % in naïve rats). Polyprenols 10 mg/kg moderately activated explorative behavior 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 did not perform a significant antidepressant effect. At last, in passive avoidance test, 30 % of rats have not learned after psychogenic stress, and the learned 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.