Figure 7.

Impaired fear conditioning in CB-Cbln1-null mice. A–H, Phenotypes of adult (3- to 5-month-old) CB-Cbln1-null mice. Adult CB-Cbln1-null mice showed significantly shorter latency to fall in the rotarod test (A; ***p = 1.68 × 10⁻⁸), but normal acoustic startle response (B). Control (Cbln1^flox/flox), n = 10, CB-Cbln1-null, n = 11. Acquisition (C) and retention/retrieval at 10 min (D) and 24 h (E) after conditioning were impaired in adult CB-Cbln1-null mice (**p = 0.00145; ##p = 0.0000717; ††p = 0.000949; §§p = 0.00472; *p = 0.0138; control (Cbln1^flox/flox), n = 7, CB-Cbln1-null, n = 10). No differences were observed in acquisition (F) and retention/retrieval of fear memory at 10 min (G) and 24 h (H) after conditioning between control (wild-type) and Grin2C^Cre/+ mice at 3–5 months of age. Control, n = 10, Grin2C^Cre/+, n = 11. I–O, Phenotypes of juvenile (1-month-old) CB-Cbln1-null mice. Juvenile CB-Cbln1-null mice showed significantly shorter latency to fall in the rotarod test (I; ***p = 1.14 × 10⁻⁶; control (Cbln1^flox/flox), n = 10, CB-Cbln1-null, n = 10). Acquisition (J) and retention/retrieval of contextual and cued fear memory at 10 min (K) and cued memory at 24 h (L) after conditioning were impaired in CB-Cbln1-null mice at 1 month (*p = 0.0234; ##p = 0.000865; ††p = 0.00934; §§p = 0.00489; control (Cbln1^flox/flox), n = 9, CB-Cbln1-null, n = 11). Subpopulations of control mice that showed less freezing and CB-Cbln1-null mice that showed more freezing were selected arbitrarily in post hoc analyses so that both groups showed a similar levels of acquisition of fear memory (M). The subpopulations of juvenile CB-Cbln1-null mice showed similar levels of freezing responses to those shown by control (Cbln1^flox/flox) mice (N, O; control, n = 7, CB-Cbln1-null, n = 7).