Systematic Analysis of the Cytokine and Anhedonia Response to Peripheral Lipopolysaccharide Administration in Rats
Experimental design of the sucrose preference tests performed using fluid undeprived rats. In the familiarization phase, rats were presented for 24 h with two water-filled bottles (W/W) on familiarization day 1 (FAM1) and FAM3, or one water- and one 1% sucrose-filled bottle (W/S) on FAM2 and FAM4. In all studies, the test phase started by injecting the rats with LPS (0.63 mg/kg, i.p.) or vehicle. 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). The effect of repeated systemic LPS injection on anhedonia was evaluated by preceding the test phase by a preexposure phase during which rats received a daily i.p. injection of 0.63 mg/kg LPS or vehicle for 5 consecutive days (LPS1–LPS5) (b). To assess the effect of stress on LPS-induced anhedonia, the test phase was preceded by a manipulation phase during which rats were subjected to 1 h of restraint stress daily for 5 consecutive days (Stress 1–Stress 5) (c).