Resumo

Objectives: Previous research by our group has demonstrated depressive-like effect of rotenone treatment in the forced swimming test. Thus, the aim of this study was to investigate depressive-like behavior in rotenone-treated animals in the sucrose preference test. Methods: Rats Wistar were given intraperitonial injections of rotenone (2.5 mg/kg) or vehicle (sunflower oil) daily up to 10 days. Open field test was performed in the 21st day of experiment. In the day after, rats were housed two per cage, separated by an aluminium wall and both were offered 2 bottles of water for 3 days. From 25th day to 28th day of experiment, sucrose solution preference was measured in an ascending concentration of sucrose (0.25%, 0.5%, 1%). In a second experiment, another protocol of sucrose preference test was used. One day before the begging of treatment, only rats with sucrose preference above 60% were selected to continue the study. Rats were food and water deprived and separated two per cage for 16 hours. Then, the bottles with water and sucrose (1%) were offered for 1 hour. In the 14th, 21st and 28th day of experiment, the same protocol was performed. Protocols were approved by the Ethics Committee in Animal Experimentation (CEEA) of UFPR (number 0144). Data are shown as mean ± SEM. Significancy was set at p<0.05. Results Rotenone group showed significant increase in the rearing frequency compared to control group (36.3 ± 2.7 vs 27.7 ± 2.3) and also immobility time (20.2 ± 5.3 vs. 6,9 ± 1.8). The rotenone group had significant higher preference for sucrose 0.5% than control group (83.9 ± 4.4 vs. 64.0 ± 7.8). In the second experiment, in the 28th, the rotenone group also had higher sucrose preference compared to controls (75.5 ± 2.09 vs. 63.7 ± 2.6). The sucrose preference in the control group decreased in the 28th day whereas the same was not observed in the rotenone group. Conclusions These results demonstrated that rotenone promoted an increase in sucrose preference and might be explained by a compensatory mechanism. It would be interesting to test these animals for a longer period to confirm this hypothesis. Moreover, further neurochemical studies will help us to understand how rotenone induces these behavioral responses.