LPS injection.

Male mice and resident female mice were injected intraperitoneally with bacterial LPS at 6 or 12.5 mg/kg (E. coli, serotype O111:B4, Sigma-Aldrich, St Louis, MO). LPS was prepared in aqueous sterile saline, aliquoted into 0.75-mL microcentrifuge tubes, and stored at –80 °C. On injection days, LPS was removed from storage, warmed to room temperature, and vortexed before the injection was administered. LPS samples remained at room temperature for less than 30 min and were not refrozen or reused.