Neuronal activation in response to amyl acetate and TMT in Cnga2 -null mice. A. A neutral odorant, amyl acetate, robustly induced c-fos expression in the OB in both wild type (A1) and Cnga2-null (A1’) mice. Inset in A1 shows magnified view of the boxed area. B. Responses of mice after presentation of TMT, a predator odor from fox. TMT-induced avoidance behaviors were present in wild type mice but absent in Cnga2-null mice (number of withdrawal, B1 left). Unlike wild type mice, Cnga2-null mice showed increased investigating behaviors for TMT (number of crouching over, B1 right). After exposure to TMT for 30 min, expression of c-fos was induced in both wild type and Cnga2-null mice in the OB (B2, B2’, respectively) and the AOB (B3, B3’, respectively). Scale bars: (A1, A1’, B2, B2’) 500 μm, (B3-B3’) 100 μm.