RESUMEN
The forced swimming test is an animal model that is sensitive to the different antidepressant treatments. On the other hand, it is also sensitive to the characteristics changes suffered by animals that have been previously exposed to different depression models. In the present study we xplored the effects on inescapable shock on the forced swimming test, during different phases of the rat estrous cycle. There was an increase of the immobility during diestrus as compared to estrus. Furthermore, inescapable shock increased the immobility, byt only during diestrus. Thus the differences found between both phases of the estrous cycle were accentuated. Due to the fact that diring diestrus there is an absence of progesterone, and that depressed women exacerbate their symptoms during the premenstrual phase, the authors suggest that the immobility registered during the forced swimming test may be useful in the study of premenstrual depression