INESCAPABLE SHOCKS ACCENTUATE FLUCTUATIONS OF FORCED SWIMMING IMMOBILITY IN DIFFERENT PHASES OF THE RAT ESTROUS-CYCLE

The forced swimming test is an animal model that is sensitive to the d ifferent antidepressant treatments. On the other hand, it is also sens itive to the characteristic changes suffered by animals that have been previously exposed to different depression models. In the present stu dy we explored the effects of inescapable shocks on the forced swimmin g test, during different phases of the rat estrous cycle. There was an increase of the immobility during diestrus as compared to estrus. Fur thermore, inescapable shocks increased the immobility, but only during diestrus. Thus, the differences found between both phases of the estr ous cycle were accentuated. Due to the fact that during diestrus there is an absence of progesterone, and that depressed women exacerbate th eir symptoms during the premenstrual phase, the authors suggest that t he immobility registered during the forced swimming test may be useful in the study of premenstrual depression.