Behavioral studies in NEP-deficient mice and their wild-type controls.

<p>(a–c) Morris water maze: (a) Comparison of 6-month-old NEP-knockout mice (dotted line with open circles; n = 24) and their wild-type age-matched littermates (line with open quadrates; n = 19). Group means of escape latencies for the first trial per day to reach the platform ±s.e.m. in sec. Where standard variation is not visible it is within the symbols (b) Comparison of 21-month-old NEP-knockout mice (dotted line with filled circles; n = 12) and their wild-type age-matched littermates (line with filled quadrates; n = 9). Group means of escape latencies for the first trial per day to reach the platform ±s.e.m. in sec; statistical analyses by repeated measures of ANOVA (<i>P</i> = 0.016). (c) Comparison of time (in sec) animals needed to find the platform at both investigated time points; data were pooled for the three days of the experiment and plotted; statistical analysis by Student's t test (**<i>P</i><0.01). (d) Shuttle box: group means of the number of conditioned reactions ±s.e.m. of 21-month-old NEP-knockout mice (filled bars; n = 12) and their wild-type littermates (open bars; n = 10) during a training interval on five training days in this two-way active avoidance paradigm. Statistical analysis by repeated measures of ANOVA (**<i>P</i><0.01). (e) Marble burying test: Comparison of the number of marbles that have been buried by 21-month-old NEP-knockout mice (filled bars; n = 9) and their wild-type littermates (open bars; n = 11). Average±s.e.m., statistical analysis by Student's t test (*<i>P</i><0.05).