Research Article

Systematic Analysis of the Cytokine and Anhedonia Response to Peripheral Lipopolysaccharide Administration in Rats

Figure 1

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).