[Study of self-regulating behavior at different stages of psychogenic stress before the formation of depressive-like state in rats].

During last decades abnormalities of neuro-psychic sphere have become a topic of great interest. Among them an important place takes depression. Psychogenic factors are commonly the most frequent cause of depressive condition, and till now the study of so-called transitional period (from the beginning of stressor action till the formation of depressive state) continues to be an actual task of scientific research. Minding this, we studied the self-regulating behavior in rats in different stages of psychogenic stress till the formation of depression-like condition. To access the behavioral changes, the "open field" test, FST (forced swimming test, "Porsolt" test) and TST (tail suspension test) were used. We also registered behavioral indices while applying stressors. Stress was applied in a modified shuttle chamber. At the very beginning of the study (the first stage of stress-alarm) an animal was forced to develop a reaction of active avoidance on metronome beats (100 beats per second), later, after its fixation, the same reaction was developed on tone (500 Hz). Then simultaneous testing of two developed reactions of active avoidance was performed (the second stage of stress). After the long-term application of stressors (48 days) the second stage of stress proceeds into the deep (the third) one. On this stage animals showed decreased motor activity in the "open field" test, decreased mobility in FST and TST, changes being statistically valid. All behavioral changes indicating depression-like condition in the animals were normalized after per os administration of antidepressant Fluoxetine at doses of 40 mg/kg. The results obtained in the study confirm that on different stages of psychogenic stress changes in behavioral indices are natural and self-regulating. They appear to be compensatory as only on their exhaustion the depression-like condition is formed.