Figure 1. VNO function is necessary for the display of innate behavior induced by predator odors.

(A) Left: behavioral arena, odor stimulus is indicated by blue swirls in area 1. Middle: naïve mice are attracted to area 1 containing control odors but avoid cat odors in the same area. Right: quantification of risk-assessment behavior (see Suppl. Exp. Procedures and Video S1 for description of risk assessment behavior and scoring details). (B) TrpC2 function is necessary for the display of risk assessment and avoidance behaviors stimulated by cat odors. (C) Plasma ACTH concentration increases in response to physical restraint (restr) and cat odor but not to control odor eugenol (eug). (D) Risk assessment behavior in TrpC2+/+ and −/− littermates exposed to rat (left) or snake (right) odors. (E) Behavioral outputs in wild-type animals exposed to an ethologically relevant complex stimulus (rabbit urine, white bars). (F) Exposure to the generally aversive odorant naphthalene (NPHT) induces robust avoidance behavior independent of TrpC2 function, and no risk assessment. Black bars in (E) and (F) indicate animals exposed to control odors, blue bars show animals exposed to kairomone odors. n=8-20; *P<0.05; **P<0.01; ***P<0.001; n.s., non-significant; Student’s one-tailed t-test (A, bar graphs in B & D) or ANOVA followed by Tukey-Kramer HSD post-hoc analysis (C, E, F and time course in B). Mean ± SEM. Control odors (ctrl) are PBS-soaked gauze (rat bar graph in D, E, and F) or clean dry gauze (all other panels). See also Fig. S1.