Doxorubicin-Induced Cardiomyopathy in Rats: Behavior of the Animals in the Open Field

Under conditions of the open field test, 30 control Wistar rats and 30 rats with experimental cardiomyopathy (CMP) were examined with recording of four behavioral indices, (i) number of crossed squares (intensity of locomotion), (ii) number of rearings (vertical stands), (iii) number of examined holes in the arena, and (iv) number of grooming episodes, within a 28-day-long observation period. The CMP state was induced by five i.p. injections of 5.0 mg/kg of doxorubicin with one-week-long intervals. As was found, all behavioral indices of control rats demonstrated considerable (sometime statistically significant) variations within the observation period (this fact has probably attracted insufficient attention in analogous experiments with long-lasting observation periods). The development of doxorubicininduced CMP resulted in considerable suppression of all types of behavioral activity, relatively moderate within the first week of observation and dramatic within late phases of the observation period. The dynamics of the numbers of rearings and grooming phenomena were complex, with noticeable increases on days 3 and 14. The dynamics of the numbers of rearings and inspection of the holes in both experimental groups were significantly dissimilar, which indicates that these behavioral phenomena are related to different aspects of the research/orientatinal activity. In general, a state of increased anxiety followed by the development of a depression-like state was observed in CMP rats. These negative shifts in behavioral activity are believed to result from general CMP-induced insufficiency of blood supply of the brain and development of hypoxia in the latter; specific direct effects of doxorubicin on some cerebral structures seem to be unlikely.