Lack of anxiolytic-like effect of diazepam in 5-HT1A receptor KO mice demonstrated in elevated plus maze (A, B) and in open field (C, D). Number of animals for each dose and treatment were as follows: WT, n = 8; KO,n = 8 for the elevated plus maze; and WT,n = 7; KO, n = 7 for the open field. Insets display the increased anxiety of KO mice (open bars) compared with WT animals (filled bars) measured as a decrease in the number of entries into the open arm (inset inA) and time spent in the open arm (B), as well as a decrease in the number of entries into the center (C) and time spent in the center (D). Total locomotor activity, measured in open field, is represented by the total number of crosses (E). Decreased sensitivity to the sedative effect of pentobarbital, measured as time to regain righting reflex after a 65 mg/kg dose (F) and as a cumulative dose of the drug required for deep anesthesia (G). Number of WT and KO animals per group in the experiments displayed inF and G were n = 9 and n = 14, respectively. *p < 0.05 represents significant difference between KO and WT animals.