Ž
3
. runway 200 = 10 = 10 cm
had non-transparent walls and a transparent lid on top Ž
. Fig. 1c . The goal box at the end of the runway was covered with saw dust. The lines
were tested in rotating order. The testing sequence of all mice was similar for both testing days. Latency times to reach the 25, 50, 100, 150 and 200 cm marks of the
Ž .
runway were recorded Fig. 1c . 2.5. Data handling and statistical analysis
Ž .
The SAS program was used for the statistical analysis of all traits SAS, 1985 . Line differences for the individual traits were tested with the model: Y s m q L q e , where
i j i
i j
Ž .
m s overall mean, L s effect of line i control, selection and e s error term of
i i j
Ž
2
. animal j of line i, e NID 0,s
. Y denotes all traits tested with this model, all as
i j e
i j
measured on animal j of line i: the cumulative number of squares crossed in 5, 10, 15, 20, 25 and 30 s in OF1 and OF2, the number of lines crossed in the centre of OF2,
LGA, GA–GB, REACHED, DEAD-END and RETURNS in M1 to M7, the frequen- cies of ‘fighting’, ‘submissive upright’, ‘immobility’, ‘social investigation’, ‘jumping’,
‘upright’, ‘sniffing’, ‘locomotion’, ‘grooming’ and ‘miscellaneous’ in the social con- frontation test, and the latency times for reaching 25, 50, 100, 150 and 200 cm of RW1
and RW2.
Trends and line differences in trends for cumulative number of squares crossed in Ž
. OF1 and OF2 over time 5 to 30 s , LGA, GA–GB, REACHED, DEAD-END, and
Ž Ž
RETURNS in the maze tests over testing day M1 to M7, excluding M6 extra-maze cue ..
Ž .
change , and latency times in RW1 and RW2 over distance reached 25 to 200 cm are tested by fitting linear regression functions to the data.
Contrasts are generated to compare cumulative number of squares crossed at 5, 10, 15, 20, 25, and 30 s in the open-field test and for reaching 25, 50, 100, 150 and 200 cm
Ž .
in the runway test between testing days OF1, OF2 and RW1, RW2 . The effect of the extra-maze cue change on day 6 of the maze test is tested by means
of t-tests testing ‘H : observed trait values s expected values as estimated from the regression lines’ against the alternative hypothesis that the observed trait values on test
day 6 differ from the expected values as estimated from the regression lines. Latency times of animals that do not reach the goal area in the maze tests are
arbitrarily set to 121 s, which is 1 s higher than the full testing time. Average GA–GB is Ž
. estimated only from animals that reach both GA and GB within time i.e., within 120 s .
Latency times for reaching, 25, 50, 100, 150 and 200 cm in the runway tests are estimated for all animals completing the runway within time and excluding individuals
that return to the start box.
3. Results
3.1. Test one: open-field test Fig. 2 presents total cumulative number of squares crossed in 5 to 30 s in OF1 and
OF2. In OF1, no significant differences exist between the lines for total cumulative
Fig. 2. Average total cumulative number of lines crossed in 5 to 30 s and standard errors in open-field test 1 Ž
. Ž
. OF1 and open-field test 2 OF2 . N s 24 per line.
number of squares crossed in 5 to 30 s. In OF2, S-line mice cross in total significantly Ž
. Ž
. more squares in 25 and 30 s P - 0.05 and more squares in the centre of the OF 8.3
Ž .
than mice of the C-line 1.8; P - 0.01 . Females of both lines cross more squares in Ž
. OF2 than in OF1 P - 0.001 .
R
2
values of the linear regression functions relating cumulative number of squares Ž .
crossed to time s are for C- and S-line females 55 and 51 in OF1 and 44 and 48 in OF2, respectively. Females of the selection line cross more squares per second
Ž .
Ž 0.18 and 0.31 in OF1 vs. OF2 than females of the control line 0.16 and 0.23 in OF1
. Ž
. vs. OF2 , but this is significant in OF2 only P - 0.05 .
3.2. Test two: maze test Average LGA, GA–GB, REACHED, DEAD-END and RETURNS in M1 to M7
are given in Table 2. S-line females reach the goal area significantly faster than C-line females in M2 to M7, but this is significantly only in M2 to M5. R
2
values of the linear Ž
Ž regression functions relating LGA to testing day M1 to M7 excluding M6 extra-maze
.. cue change
are for C- and S-line females merely 11 and 9, respectively. Negative regression coefficients indicate that the mice reach the goal area faster in subsequent
Ž .
tests 5.2 and 6.2 s per test for C- and S-line females, respectively; P 0.05 . Females that fulfilled the maze did not always fulfil the maze or increase their latency times in
subsequent tests. After reaching the goal area, S-line females enter the goal box faster than C-line
females. This is significant in M3, M6, and M7 only. The high average of the C-line in M3 is due to one animal waiting 57 s before entering the goal box. No regression lines
could be fitted to the data on GA–GB and testing day due to too many missing values. No significant differences exist between the lines and no significant trend exists over
subsequent maze tests for percentage reached of the total maze.
Table 2 Ž
. Means and standard errors between brackets of LGA, GA–GB, REACHED, DEAD-END and RETURNS
Ž .
in maze test 1 to 7 M1 to M7 M1
M2 M3
M4 M5
M6 M7
a
LGA C
111.6 114.7
100.9 106.9
100.7 81.3
79.2 Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. 3.5
2.8 6.4
6.0 7.3
8.4 8.5
UU U
U UU
S 114.9
91.5 78.9
79.4 67.4
78.8 75.3
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
3.3 7.4
8.7 8.3
9.6 9.5
9.5
b
GA–GB C
13.2 8.7
16.8 5.8
6.7 8.6
9.1 Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. 4.0
1.2 8.2
1.4 0.8
1.2 1.7
U UU
UU
S 8.3
5.6 4.9
5.5 4.9
3.8 3.0
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
3.3 0.8
1.1 0.9
1.7 0.8
0.5
a
REACHED C
71.1 78.2
84.1 75.8
71.3 72.1
78.5 Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. 5.2
3.3 3.0
4.7 5.6
6.8 6.1
S 70.3
83.3 82.9
84.6 79.2
78.0 77.7
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
3.8 4.5
4.9 4.5
6.1 6.3
6.3
a
DEAD-END C
8.7 12.4
9.1 7.0
6.6 4.5
5.3 Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. 0.8
0.7 0.9
0.9 0.8
0.8 0.8
UU
S 12.3
13.9 8.8
7.9 5.2
6.4 4.4
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
0.8 1.1
1.1 1.2
0.8 1.4
0.8
a
RETURNS C
1.0 1.5
1.1 1.3
1.2 1.6
1.0 Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. Ž
. 0.2
0.2 0.2
0.3 0.2
0.3 0.3
S 2.5
UUU
1.3 1.4
1.3 1.7
2.5 1.6
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
0.4 0.3
0.4 0.3
0.5 0.7
0.4
U
P - 0.05;
UU
P - 0.01;
UUU
P - 0.001; C sC-line; SsS-line.
a
N s 24 per line.
b
N from M1 to M7s 5, 3, 6, 4, 6, 12, and 14 for the C-line, and 4, 12, 13, 14, 14, 12 and 14 for the S-line, respectively.
Before reaching the goal area, S-line females encounter dead-ends in the maze significantly more often than C-line mice in M1; no significant differences between the
lines exist for M2 to M7. R
2
values of the linear regression functions relating Ž
Ž ..
DEAD-END to testing day M1 to M7 excluding M6 extra-maze cue change are for
C- and S-line females 16 and 30, respectively. Negative regression coefficients Ž
indicate that the females encounter fewer dead-ends in subsequent tests 0.9 and 1.6 .
dead-ends per test for C- and S-line females, respectively ; regression coefficients are Ž
. significantly more negative in S- than in C-line females P - 0.01 .
Before reaching the goal area, S-line females return more often to the starting area than C-line mice in M1; no significant line differences exist in subsequent tests. No
significant trend exists over subsequent maze tests for RETURNS. Ž
. None of the values for DEAD-END and LGA in M6 extra-maze cue change differ
significantly from the expected values as predicted from the regression lines. 3.3. Test three: social confrontation test
Average frequencies of ‘immobility’, ‘social investigation’, ‘upright’, ‘sniffing’, ‘locomotion’ and ‘grooming’ are given in Table 3. None of the animals scored for
Table 3 Ž
. Means and standard errors
between parenthesis of frequencies of ‘immobility’, ‘social investigation’,
‘upright’, ‘sniffing’, ‘locomotion’ and ‘grooming’ in the social confrontation test. C sC-line; SsS-line
a
Immobility Social investigation
Upright Sniffing
Locomotion Grooming
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
C 0.0 0.0
8.1 0.8 4.5 0.5
13.5 0.7 3.9 0.3
0.1 0.1
UU UU
UUU
Ž .
Ž .
Ž .
Ž .
Ž .
Ž .
S 0.1 0.1
5.5 0.5 5.6 0.6
10.5 0.7 8.0 0.7
0.3 0.1
UU
P - 0.01.
UUU
P - 0.001.
a
N s 24 per line.
‘fighting’, ‘submissive upright’, ‘jumping’ and ‘miscellaneous’. No significant differ- ences exist between the lines for ‘grooming’, ‘immobility’ and ‘upright’. S-line mice
score significantly higher for ‘locomotion’ and significantly lower for ‘sniffing’ and ‘social investigation’.
3.4. Test four: runway test Ž .
Average latency times s for reaching the 25, 50, 100, 150 and 200 cm marks in RW1 and RW2 are given in Fig. 3. In RW1 three, and in RW2 one S-line female are
excluded from the analyses because they returned to the start box. S-line females have lower latency times at all distances in RW1 and RW2. This is significant at all distances
Ž .
in RW1 P - 0.01 at 25 cm; P - 0.001 at 50 to 200 cm , but only at 150 and 200 cm in Ž
. RW2 P - 0.05 . Females of both lines are significantly faster in RW2 than in RW1
Ž .
P - 0.01 . R
2
values of the linear regression functions relating distance reached in RW1 and Ž .
RW2 to time s are for C- and S-line females 41 and 64 in RW1 and 64 and 49 in RW2, respectively. The intercept, a measure of time taken before entering the RW, is
Ž .
significantly different from 0 in C-line females in RW1 P - 0.001 , but not in S-line
Ž . Fig. 3. Average latency times s for reaching 25, 50, 100, 150 and 200 cm and standard errors in runway test
Ž .
Ž .
1 RW1 and 2 RW2 . N s 24 per line.
females and not in either line in RW2. In both tests, S-line females run significantly Ž
. Ž
faster 0.05 and 0.04 s per cm in RW1 vs. RW2 than C-line females 0.08 and 0.05 s . Ž
. per cm in RW1 vs. RW2
P - 0.01 .
4. Discussion and conclusions
