Effects of strain and genotype on maternal care behavior.

<p>Behavioral strain differences between C57BL/6N and Balb/c mothers with a glucocorticoid receptor wildtype (GR +/+) or a heterozygous deletion (GR +/−) are exemplarily presented for four different behavioral measures: (A) ‘licking/grooming’, (B) ‘passive nursing’, (C) ‘self-grooming out of nest’ and (D) ‘climbing/digging’. While strains were found to differ significantly in all four measures, GR genotype did not affect the behavior. Moreover, a significant strain-by-genotype-interaction was found with respect to ‘licking/grooming’. While C57BL/6N +/+ dams spent more time ‘licking/grooming’ than Balb/c mothers of both GR genotypes, no difference was found between C57BL/6N +/− mothers and Balb/c dams. Data are presented as untransformed means ± standard error of the mean, * p<0.05, ** p<0.01.</p

Ethogram used for the assessment of maternal care behavior in C57BL/6N and Balb/c dams.

<p>Behavioral measures are categorized according to their presumed function in ‘self-maintenance’, ‘caring’ and ‘neglecting behavior’.</p

Summary of all data generated by behavioral observations and the pup retrieval test.

<p>Data analysis was done using GLMs on the basis of 26 dams belonging to four different treatment groups: Balb/c wildtypes (+/+; n = 7), Balb/c with a heterozygous mutation of the GR (+/−; n = 6 for behavioral observations, n = 5 for the pup retrieval test) C57BL/6N wildtypes (+/+; n = 6), C57BL/6N with a heterozygous mutation of the GR (+/−; n = 7). Data are given as untransformed means ± standard error of the mean (s.e.m.). The statistical analysis is summarized with respect to the transformation used (NT = not transformed, sqrt = square root transformation, angular = angular transformation) and the effects of “strain”, “GR genotype” and “strain-by-GR-genotype-interaction” (T = tendency; *p<0.05, **p<0.01).</p

Complete list of behavioral measures used for the analysis and the transformations applied to meet the assumptions of parametric analysis (NT = no transformation, log = log₁₀(y+1)-transformed, sqrt = square-root-transformed, angular = arcsin(square-root(y))-transformed).

<p>Complete list of behavioral measures used for the analysis and the transformations applied to meet the assumptions of parametric analysis (NT = no transformation, log = log₁₀(y+1)-transformed, sqrt = square-root-transformed, angular = arcsin(square-root(y))-transformed).</p

Variation of strain main effects across the six laboratories in both designs.

<p>For each laboratory and experimental design, the main effect of ‘strain’ was separately calculated and displayed in terms of the mean F-ratio (+ s.e.m., square-root-transformed) across all 29 behavioral measures. Although the strain effect varied considerably among laboratories in the heterogenized design, the standardized design produced even more variable outcomes. Moreover, average F-ratios for ‘strain’ were considerably higher in the standardized design, indicating that treatment effects may be systematically overestimated by standardization.</p

F-ratios of all behavioral measures for the main effects of ‘strain’ and ‘laboratory’ based on the GLM (split by experimental design): y = strain+laboratory+strain×laboratory; p≤0.001***, p≤0.01**, p≤0.05*, p>0.05 NS.

<p>F-ratios of all behavioral measures for the main effects of ‘strain’ and ‘laboratory’ based on the GLM (split by experimental design): y = strain+laboratory+strain×laboratory; p≤0.001***, p≤0.01**, p≤0.05*, p>0.05 NS.</p

Variation between laboratories in the standardized and in the heterogenized design.

<p>The variation in strain differences is displayed as mean F-ratios (+ s.e.m.) of the ‘strain-by-laboratory’ interaction term calculated for 29 behavioral measures. F-ratios were determined separately for the two experimental designs, square-root-transformed to meet the assumptions of parametric analysis, and then compared using a GLM blocked by ‘behavioral measure’. F-ratios of the ‘strain-by-laboratory’ interaction terms were significantly lower in the heterogenized design (F_1,28 = 4.222, p = 0.049), indicating lower between-experiment variation.</p

Between-experiment variation versus within-experiment variation.

<p>To assess the relative weight of between-laboratory variation versus within-laboratory variation, an F-ratio was calculated that reflects the partitioning of the ‘strain-by-block’ variance between all 24 blocks of one experimental design into variance due to variation between laboratories and variance due to variation within laboratories. For this, the mean squares of the ‘strain-by-laboratory’ interaction term were divided by the mean squares of the ‘strain-by-block’ interaction term. Data are displayed as mean F-ratios (+ s.e.m.; square-root-transformed) across all 29 behavioral measures for both conditions. F-ratios were significantly smaller in the heterogenized design (F_1,28 = 4.678, p = 0.039), demonstrating that heterogenization increased within-experiment variation relative to between-experiment variation.</p

Number of stretched postures on the elevated zero maze shown by C57BL/6NCrl and DBA/2NCrl mice.

<p>Data are presented as means (+ s.e.m., square-root-transformed, n = 16/strain and laboratory). The example illustrates large effects of the laboratory in the standardized (<b>A</b>) and heterogenized (<b>B</b>) design. Moreover, the direction of strain difference differed between Giessen and Munich in the standardized design.</p

Laboratory-specific testing procedures and apparatuses.

<p>Laboratory-specific testing procedures and apparatuses.</p