Graduate Thesis Or Dissertation

 

Temporal maternal behavior patterns in two inbred lines of mice and reciprocally cross-fostered individuals Pubblico Deposited

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  • The location of a lactating mouse in a cage of two compartments, a nest area and a larger wire cage, was continuously recorded for ten days after parturition. Three experimental groups within each of two inbred lines, A/J and C57BL/6J, were tested: first generation, unfostered; second generation, unfostered; and second generation, crossfostered. In both lines, the time spent away from the litter increased linearly with day (b = 25 minutes per day). C57 mothers spent about 1. 1 hours more per day away from the nest than A/J mothers, 3.3 vs 2.2 hours on day 1 and 7.5 vs 5.5 hours on day 10. The average trip length increased linearly with day (b = 0.61 minutes per day); trip lengths for days 1 and 10 were 103 and 7.2 minutes, respectively. The average number of trips per day was 103 but the 10 day pattern differed between the lines. In the C57 line it decreased linearly (b = -6 trips per day) while in A/J mothers an initial increase was followed by a decrease to day 1 levels, Larger estimated differences among the experimental groups and among individuals were found in A/J mothers while a larger proportion of the variation was attributable to daily changes in C57 mothers. Significant line x maternal line interaction terms indicated a fostering effect rather than maternal line effects was present. Crossfostered A/J mothers averaged 1.0 hour less away from the nest, 14 more trips daily and 2.1 minutes less per trip than unfostered mothers, Crossfostered C57 mothers averaged 22 more trips daily, Generation differences were found. Generation 1 individuals of both lines averaged 0.4 hours longer away from the nest daily, Generation 1 A/J mothers averaged 92 more trips daily and had trip lengths 4.1 minutes shorter. Generation 1 C57 mothers averaged 18 more trips daily but no difference in trip length was found. When litter size and weight were included in the regression model, time out per day and trip length increased with the litter parameters in the A/J line. In the C57 line time away from the nest and trip length increased as litter weight increased, but decreased as litter size increased. In open field testing members of the A/J line had average ambulation and defecation scores of 2.3 and 4.2 under white light and 44.5 and 3.2 under red light. Members of the C57 line had average ambulation scores of 315 under white light and 353 under red light. The defecation score averaged about 0.7 under both regimes. Line differences in circadian rhythms were noted. A/J mothers averaged 13% of the time away from the nest per day during the 14 hour light interval vs 47% for C57 mothers. Circadian rhythms of both lines were characterized by a prominent activity peak stimulated by darkness onset. In A/J mothers activity began abruptly after darkness onset while C57 mothers activity increases were noted in hours prior to darkness onset. A secondary peak of activity occurred in early morning hours in A/J mothers and at variable times in the C57 mothers. In both lines the second generation unfostered group, which experienced the most constant pre and postweaning environment, showed the least nocturnal tendency. This group in the C57 line displayed the largest proportion of the time away from the litter and trips and had longer trip lengths in light than dark, and had higher levels of general activity in light; the secondary peak of activity occurred after light onset. In the other two C57 groups, behavior measures were higher and the secondary activity peak occurred in darkness. The second generation unfostered A/J group had a third peak of activity during light, unlike the other groups.
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