Figure 2. Red light exposure elicits splenomegaly, while splenectomy reverses red light exposure-induced cognitive deficits in septic mice. (A) Treatment schedule. Mice were treated with or without LPS (10 or 20 mg/kg), and then were exposed to light for up to seven days. The mice were euthanized and their spleens were collected on day 1, 3 or 7. (B) Red light exposure resulted in splenomegaly in LPS (20 mg/kg)-administered mice on days 3 and 7 relative to ambient white light or green light exposure. (C) Red light exposure led to splenomegaly in LPS (10 mg/kg)-treated mice on day 7 compared to green light exposure. (D) Red light exposure induced significant spleen enlargement in non-LPS-treated mice on day 7 relative to ambient white light and or green light exposure. (E) Treatment schedule. Mice underwent a splenectomy or sham surgery 14 days prior to LPS (20 mg/kg) administration, and were then exposed to light for seven days. On day 8, open field and Y maze tests were performed. On day 11, a NORT was performed. (F–K) Splenectomy reversed red light exposure-induced cognitive dysfunction and anxiety-like behavior, as demonstrated by the lack of significant difference in the frequency of entering the novel arm (F) and the time spent in the novel arm (G) in the Y maze test, the time spent in the center (H) and the freezing time (I) in the open field test, and the time exploring the novel object (J, K) in the NORT between splenectomized mice exposed to ambient white light or red light. Data are shown as the mean ± SEM (n = 6-8/group). N.S., not significant, *P < 0.05, #P < 0.05, ##P < 0.01.