Systematic Analysis of the Cytokine and Anhedonia Response to Peripheral Lipopolysaccharide Administration in Rats
Systemic LPS injection reduces body weight, fluid intake, and sucrose preference in the sucrose preference test. An optimized sucrose preference test was used to evaluate the anhedonic response to LPS. During the familiarization phase of the experiment ((a–c) left panels), rats were exposed to 2 bottles of water (W/W) on familiarization day 1 (FAM1) and FAM3, while on FAM2 and FAM4 one bottle was filled with water and the other bottle contained a 1% sucrose solution (W/S). Three days after the familiarization phase, rats were injected i.p. with 0.63 mg/kg LPS or vehicle and voluntary consumption of water and sucrose was measured during a period of 24 h for 4 days (D1–D4) in the test phase ((a–c) right panels). Note that the growth rate of rats during each day of the familiarization phase was evaluated by calculating the body weight change (ΔBW) against their weight at the first day of the familiarization phase ((a) left panel). Growth rate in the test phase is presented as the body weight change at each day compared to the rats’ weight right before LPS administration. Dashed lines in (c) indicate chance level for sucrose preference. Graphs are plotted as mean + SEM and represent pooled data from 3 separate but identical studies using 12 naive animals per treatment group in each experiment (total per treatment group). Data were analyzed by rmANOVA followed by independent samples -test. , , , and compared to vehicle.