A-15 Free Communication/Slide - Immunology: MAY 27, 2009 9:30 AM - 11:00 AM ROOM: 4C4
It is well known that infection decreases physical activity performance in humans and animals, but the mechanisms is unknown. Many researches have used lipopolysaccharide (LPS) as a model of bacterial infection to induce sickness behavior. However, how voluntary physical activity is regulated during viral infection is not known. The pathogen-associated molecular patterns (PAMPs) are recognized by the family of toll-like receptor (TLRs) on host mammalian cells which signal host cells to induce a response. Among synthetic double-stranded (ds) RNAs, polyriboinosinic: polyribocytidylic acid (poly I:C) activates immune function via TLR3. Additionally, among synthetic single-stranded (ss) RNAs, R848 activates it via TLR7/8.
PURPOSE: To determine whether dsRNA and ssRNA are responsible for reduced spontaneous physical activity, we measured poly I:C- and R848-induced changes in voluntary wheel-running activity in mice.
METHODS: In this experiment, the C3H/HeN mice were injected with poly I:C and R848 (0, 1, and 5 mg/kg, i.v., respectively) and then the wheel-running activity of mice were measured for 24 hours.
RESULTS: In these experiments, poly I:C and R848 treatments significantly increased plasma IFN-b and IFN-a. Low and high dose of poly I:C treatments significantly reduced wheel-running activity (37% and 70% compared with pre-injection, respectively). Additionally, R848 treatments also dose-dependently reduced wheel-running activity (33% and 67% compared with pre-injection, respectively).
CONCLUSION: Our results suggest that the transient reduction in physical activity after dsRNA and ssRNA injection is induced dose dependently. In conclusion, ligation of TLR3 and TLR7/8 reduce running wheel activity. Future investigations need to determine which protein products are responsible for this reduction.