Out Like a Light? The Effects of a Diurnal Husbandry Schedule on Mouse Sleep and Behavior

Abstract

Sleep disruption in humans, caused by shift work, can be detrimental to physical and behavioral health. Nocturnal laboratory mice may experience a similar disruption caused by human daytime activities, but whether this disruption affects their welfare is unknown. We used 48 mice (CD1, C57BL/6, and BALB/c of both sexes) in a factorial design to test a sleep disruption treatment, in which mice were disturbed by providing routine husbandry at either 1000 or 2200 during a 12:12-h light:dark cycle, with lights on at 0700. All mice were exposed for 1 wk to each disruption treatment, and we used a noninvasive sleep monitoring apparatus to monitor and record sleep. To determine whether providing nesting material ameliorated effects of sleep disruption, we tested 4 amounts of nesting material (3, 6, 9, or 12 g) and continuously recorded sleep in the home cage for 2 wk. C57BL/6 mice, regardless of sex or disruption timing, slept the least overall. There was a strong interaction of sex and type of mouse on sleep across 24 h. Mice slept less during the first day of the daytime disturbance than on day 6. These results suggest that disturbance timing affects sleep patterns in mice but not their overall amount of sleep and that the changes in sleep patterns vary between mouse type and sex. In addition, mice appear to both anticipate and acclimate to human activity during the day. Our welfare checks were possibly too predictable and inconsequential to induce true sleep disruption.

Figure 1.

Sleep apparatus. Left, top view; right, C57BL/6 mouse and nesting material in apparatus.

Figure 2.

Ethogram for behavior coding. Includes both scan sampling and 1/0 sampling behaviors. Maintenance and nesting categories had subsets of behaviors, but subsets were binned into categories for analysis.

Figure 3.

Average percentage of time spent sleeping during daylight hours. Solid bars, daytime (1000) disturbance; checkered bars, nighttime (2200) disturbance. Different letters indicate within-sex differences; bars with asterisks indicate between-sex differences (Tukey, P < 0.05). Data are presented as least-squares mean ± SE.

Figure 4.

Average sleep bout length during daylight hours. Solid bars represent daytime disturbances; checkered bars represent nighttime disturbances. Different letters indicate within-group differences (P < 0.05, Tukey); asterisks indicate between-group differences (P < 0.05, Tukey). Data are presented as least-squares mean ± SE.

Figure 5.

(A) Percentage of time spent sleeping per 2-h interval, by type of mouse, daytime disturbance. Significant (P < 0.05) differences between C57BL/6 and Balb/c mice (*), between Balb/c and CD1 mice (†), and between CD1 and C57BL/6 mice (£) are indicated. (B) Percentage of time spent sleeping per 2 h interval by type of mouse, nighttime disturbance. Significant (P < 0.05) differences between C57BL/6 and Balb/c mice (*), between Balb/c and CD1 mice (†), and between CD1 and C57BL/6 mice (£) are indicated. (C) Percentage of time spent sleeping per 2-h interval by day of treatment, daytime disturbance. Significant (P < 0.05) differences between days 1 and 6 (*), between days 1 and 3 (†), and between days 3 and 6 (£) are indicated. (D) Percentage of time spent sleeping per 2 h interval by day of treatment, nighttime disturbance. Significant (P < 0.05) differences between days 1 and 6 (*), between days 1 and 3 (†), and between days 3 and 6 (£) are indicated. Open bar, lights on; solid bar, lights off. Data are presented as least-squares mean ± SE.

Figure 6.

(A) Percentage of time spent sleeping per 2-h interval by type of mouse, female mice. Significant (P < 0.05) differences between C57BL/6 and Balb/c mice (*), between Balb/c and CD1 mice (†), and between CD1 and C57BL/6 mice (£) are indicated. (B) Percentage of time spent sleeping per 2-h interval by type of mouse, male mice. Significant (P < 0.05) differences between C57BL/6 and Balb/c mice (*), between Balb/c and CD1 mice (†), and between CD1 and C57BL/6 mice (£) are indicated. Open bar, lights on; solid bar, lights off. Data are presented as least-squares mean ± SE.

Figure 7.

(A) Percentage of time spent sleeping per 2-h interval by amount of nesting material provided, 3 g. (B) Percentage of time spent sleeping per 2-h interval by amount of nesting material provided, 6 g. (C) Percentage of time spent sleeping per 2-h interval by amount of nesting material provided, 9 g. (D) Percentage of time spent sleeping per 2-h interval by amount of nesting material provided, 12 g. Open bar, lights on; solid bar, lights off. Data are presented as least-squares mean ± SE. *, Significant (P < 0.05) difference during that epoch.

Figure 8.

Proportion of observations by behavior categories. Solid bars, male mice; checkered bars, female mice. Different letters indicate significant (P < 0.05, Tukey) differences within groups. Data are presented as least-squares mean ± SE.

Figure 9.

Proportion of time observed in behavior categories. Solid bars, lights on; checkered bars, lights off. Different letters indicate significant (P < 0.05, Tukey) differences within groups. Data are presented as least-squares mean ± SE.

Figure 10.

Nest scores affected by lights, disruption time, and day of treatment. Solid bars, daytime disturbances (1000); checkered bars, nighttime disturbances (2200). Different letters indicate within-day differences; asterisks indicate between-day differences (Tukey, P < 0.05). Data are presented as least-squares mean ± SE.

Figure 11.

Nest scores affected by sex, lights, and day. Solid bars, lights on; checkered bars represent lights out. Differing letters indicate within day differences, bars with asterisks indicate between day differences (Tukey, P < 0.05). Data are presented as least-squares mean ± SE.