CRTH2 deficiency and the CRTH2 antagonists reverse LPS-induced decreases in social and object exploratory behavior. Five micrograms of LPS (closed columns) or saline (open columns) were intraperitoneally injected into CRTH2+/+ (+/+) and CRTH2−/− (−/−) mice (A, E, I, M; n = 6–13), and CRTH2+/+ mice were pretreated intraperitoneally for 1 h with 30 mg/kg ramatroban (Ram; B, F, J, N) and pretreated intracerebroventricularly for 30 min with 1 nmol CAY10471 (CAY; C, G, K, O; n = 5–9) or 1 nmol BWA868C (BWA; D, H, L, P; n = 4–9). After LPS injection, the duration engaged in social interaction (A–D) and object exploratory behavior (E–H) at 10 h, locomotor activity at 2 h (I–L), and food intake for 24 h (M–P) were measured. Veh, vehicle. Data are expressed as the mean ± SEM; *p < 0.05, **p < 0.01 by two-way ANOVA followed by Tukey—Kramer test.