Optimization of food deprivation and sucrose preference test in SD rat model undergoing chronic unpredictable mild stress

BackgroundThe chronic unpredictable mild stress (CUMS) model has long been considered the best model for exploring the pathophysiological mechanisms underlying depression. However, there are no widely recognised standards for strategies for modeling and for behavioral testing. The present study aimed to optimize the protocols for food deprivation and the sucrose preference test (SPT) for the CUMS model. MethodsWe first evaluated the effects of different long periods of food deprivation on the body weight of Sprague Dawley (SD) rats by testing food deprivation for 24 hours (8:00-8:00(+)), food deprivation for 12 hours during the daytime (8:00-20:00) and food deprivation for 12 hours at night (20:00-8:00(+)). Next, we established a SD rat CUMS model with 15 different stimulations, and used body weight measurement, SPT, forced swim test (FST), open field test (OFT) and Morris water maze (MWM) test to verify the success of the modeling. In the SPT, consumption of sucrose and pure water within 1 and 12 hours was measured. ResultsTwelve hours of food deprivation during the daytime (8:00-20:00) had no effect on body weight, while 12 hours of food deprivation at night (20:00-8:00(+)) and 24 hours of food deprivation (8:00-8:00(+)) significantly reduced the mean body weight of the SD rats. When SPT was used to verify the successful establishment of the CUMS rat model, sucrose consumption measured within 12 hours was less variable than that measured within 1 hour. ConclusionsTwelve hours of food deprivation in the daytime (8:00-20:00) may be considered a mild stimulus for the establishment of a CUMS rat model. Measuring sucrose consumption over 12 hours is recommended for SPT.