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The temporal changes of each behavioral component. For calculating the frequency, the presence or absence of each behavior was recorded as 1/0 in each 5-sec period, and summed for each minute. Filled boxes and open boxes indicate the frequency of each one-minute period of behavior in males and females, respectively.

 

[Statistical analysis]
Two-way ANOVA (strain~sex) for repeated measures of continuous variable (time) was performed on the behavioral data (except defecation and urination).

Ambulation: There was a significant effect of strain [F(11,216) = 14.692, p < 0.0001]. C57BL/6, SWN and KJR showed higher ambulation, while MSM and JF1 were lower. There was a significant strain~time interaction [F(99,1944) = 3.118, p < 0.0001]; and ten strains, except for the PGN2 and JF1, showed significant changes across time (for all, p < 0.01). Most exhibited an initial increase in ambulation, which then stabilized or in some showed a gradual decrease. There was also a significant effect of sex~time [F(9,1944) = 2.587, p < 0.01] with females showing higher ambulation in the first three minutes. Strain~sex interaction was not significant.

Percentage of central ambulation: There was a significant effect of strain [F(11,216) = 13.028, p < 0.0001]. BFM/2 and BLG2 showed higher central ambulation, while KJR and JF1 were lower. There was a significant strain~time interaction [F(99,1944) = 1.742, p < 0.0001]; and nine strains, except for the NJL, CHD and JF1, showed significant changes across time (for all, p < 0.01). Most exhibited an initial increase of %, which then stabilized or in some showed a gradual decrease. There was also a significant effect of sex~time [F(9,1944) = 2.217, p < 0.05] with females showing higher central ambulation than male in the first half, but lower in the later session. Strain~sex interaction was not significant.

Urination: It was characteristic in MSM that all males exhibited urination. The males of BFM/2 and BLG2, and the females of JF1 showed urination in many animals, while both sexes of C57BL/6 and PGN2 rarely urinated.

Sniffing: There was a significant effect of strain [F(11,216) = 11.20, p < 0.0001]. C57BL/6 showed the highest frequency of sniffing, while CHD showed the lowest. There was also a significant strain~time interaction [F(9,1944) = 35.65, p < 0.0001]. Three strains\PGN2, HMI, and SWN\initially showed a sudden increase in sniffing frequency which remained at the same level until the end of the session, whereas in NJL, MSM, and JF1 it gradually decreased. CHD showed both an increase at the beginning and a decrease in the last half. Others showed consistently higher frequency throughout the test. Sex difference and strain~sex interaction were not significant.

Locomotion: There was a significant effect of strain [F(11,216) = 21.95, p < 0.0001] and strain~time interaction [F(99,1944) = 2.14, p < 0.0001] on locomotion. There was also a significant effect of sex~time [F(9,1944) = 3.37, p < 0.001] with females showing higher locomotion in the first three minutes. Strain~sex interaction was not significant.

Stretching: There was a significant effect of strain [F(11,216) = 9.05, p < 0.0001] and strain~time interaction [F(99,1944) = 10.37, p < 0.0001] on stretching. Sex differences and strain~sex interaction were not significant.

Leaning: There was a significant effect of strain on leaning [F(11,216) = 32.27, p < 0.0001] and strain~time interaction [F(99,1944) = 2.97, p < 0.0001] on leaning. There was no significant sex difference.

Rearing: There was a significant effect of strain [F(11,216) = 29.28, p < 0.0001] and strain~time interaction [F(99,1944) = 3.02, p < 0.0001] on rearing. There was also a significant strain~sex interaction [F(11,216) = 2.07, p < 0.05] and females indicated higher rearing in BFM/2 and CAST/Ei.

Grooming: There was a significant effect of strain on grooming [F(11,216) = 19.30, p < 0.0001]. MSM showed the highest grooming, while seven strains\C57BL/6, PGN, SWN, BFM/2, HMI, CAST/Ei, and BLG2\seldom or never showed grooming. There was a significant strain~time interaction [F(99,1944) = 2.97, p < 0.0001] and NJL, CHD, MSM and JF1 showed a gradually increasing frequency (p < 0.01). There was also a significant effect of sex [F(1,216) = 4.58, p < 0.05], with females showed higher grooming. Strain~sex interaction was not significant.

Face-washing: There was a significant effect of strain on face-washing [F(11,216) = 32.27, p < 0.0001]. BLG2 showed the highest frequency, while NJL, KJR, MSM showed lower face-washing. There was also a significant strain~time interaction [F(99,1944) = 2.97, p < 0.0001] and eight strains, except for NJL, CHD, KJR, MSM, and JF1, showed significant changes with elapse of time (for all except CAST/Ei; p < 0.01, CAST/Ei; p < 0.05). Most showed increased frequency at first, which then stabilized or gradually decreased. There was no significant sex difference.

Digging and Gnawing: Digging and gnawing appeared less frequently, but there were significant effect of strain [Digging: F(99,1944) = 9.86; Gnawing: F(99,1944) = 6.64, for both, p < 0.0001]. BFM/2 and BLG2 showed the highest frequency of digging and gnawing, respectively. On the other hand, HMI, CHD, and C57BL/6 seldom showed digging, and JF1 never showed either digging or gnawing. These behaviors tended to appear later in the session (data not shown). No sex differences were detected in these behaviors.

Jumping: There was a significant effect of strain on jumping [F(11,216) = 55.98, p < 0.0001]. PGN2 showed the highest frequency of jumping, while C57BL/6, MSM, and JF1 never showed jumping. There was also a significant strain~time interaction [F(99,1944) = 2.56, p < 0.001] and five strains, PGN2, HMI, NJL, SWN, and KJR, showed significant changes across time (p < 0.01). Most showed a gradually increasing frequency with time. There was no significant sex difference.

Pausing: There was a significant effect of strain on pausing [F(11,216) = 15.81, p < 0.0001]. BFM/2 showed the highest frequency of pausing, while HMI, CHD, C57BL/6, and JF1 showed the lowest frequency. There was also a significant strain~time interaction [F(99,1944) = 1.82, p < 0.001] and seven strains, HMI, CAST/EI, NJL, BLG2, KJR, MSM and JF1, showed a gradually decreasing frequency with time (p < 0.01). There was no significant sex difference.

Freezing: There was a significant effect of strain on freezing [F(11,216) = 8.30, p < 0.0001]. JF1 showed the highest frequency of freezing, while five strains, CAST/Ei, NJL, BLG2, KJR, and C57BL/6 seldom showed this behavior. There was also a significant strain~time interaction [F(99,1944) = 3.62, p < 0.0001]; and six strains, PGN2, HMI, CHD, SWN, MSM, JF1, showed significant changes across time (p < 0.01). Most showed a high frequency at first, which then immediately decreased, but JF1 showed a gradual reduction. There was no significant sex difference.

 


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