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Introduction
The quality of parental care is one early life experience that has an impact on cognitive ability later in life. In rodents, early maternal separation, a model for human adversity, increases later anxiety (Joushi et al., 2021).The question of whether a physically enriched environment (EE) can reduce the increase in anxiety-related behavior in maternally separated (MS) mice was investigated in a previous study from this lab (Cornwell et al., 2018). In this study mice housed in MS-only groups in an enriched environment, showed normal behavior in the open field. Our most recent study looked into whether housing MS mice in EE with control cage mates during adolescence would preserve the EE-related anxiety reduction.
General Experimental Design
Rearing Conditions:
There were 4 control and 4 MS litters housed in a vivarium with a reversed 12/12hr light/dark cycle. From postnatal day 1 (PND 1) to PND 14, MS mice were separated from their mothers for 3 hours a day in a different room away from the vivarium at a temperature of 27 °C. From P15-P20 the mice were housed continuously with their mother. Control Litters were housed continuously with their mother from birth until all litters were weaned on P21.
Environmental Enrichment and Social Mixing:
Weanlings were sexed and placed into enriched cages containing 2 MS and 2 Control mice of the same sex. The enriched environment included running wheels, food, water, toys, and tunnels. To distinguish between the C and MS litters, the mice were tailed marked every other day with sharpie pens of different colors. After two weeks of EE, on PND 36 one male and one female from each litter was tested.
Open Field Test
The Open Field test evaluates locomotor activity in an unfamiliar setting. The apparatus is consisting of 64 equal squares and is surrounded by a wall to prevent escape. After a 30-minute habituation period in the testing room the mice were individually placed in the apparatus and given 180 seconds (3 minutes) to freely explore. Testing sessions were video taped, and the films were evaluated by a student naïve to the animals' rearing histories for the number of center entries, center time and the number of boli produced.
Testing Apparatus:
Most Recent Experiment Findings
Titled: Environmental Enrichment Combined With Social Mixing Increases Stress Reactivity in Adolescent Maternally Separated CD-1 Mice
Open Field Testing:
MVI_1451.MP4(Cornwell, Catherine Summer 2022)
Results from this Study using Open Field Test:
(Figure 1)
(Figure 2)
Fig 1: Time in Center
There were no significant differences between groups in the time spent in the center t(14)=.173, p>.05 one-tailed
Figure 2: Number of Center Entries
Control mice made significantly more entries into the center than the maternally separated Mice t(14)=2.103, p<.05 one-tailed.
Environmental enrichment has been shown in earlier studies to reduce stress in rodents periodically separated from their mothers (Cornwell et al, 2018, Francis et al., 2002, Joushi et al, 2021). However, based on our test, this EE effect is blocked when MS rodents are housed with controls.
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