Presentation Title

The Effects of Augmented Maternal Care on the Learning and Memory of Mice

Faculty Mentor

Dr. Annabel K. Short

Start Date

17-11-2018 8:45 AM

End Date

17-11-2018 9:00 AM

Location

C161

Session

Oral 1

Type of Presentation

Oral Talk

Subject Area

biological_agricultural_sciences

Abstract

This study investigated how augmented maternal care affects the learning and behavior of mice by looking at both molecular and behavioral changes. Early-life experiences, especially the mother-infant relationship, play a key role in determining cognitive and emotional development. While a lack of maternal care in early life can cause a long-lasting overactive stress response in the animal, enhanced maternal care has been shown to reduce the stress response, resulting in improved learning and memory.

Previous studies in rats found that augmented maternal care causes a repression of corticotropin-releasing hormone (CRH) mRNA expression in the paraventricular nucleus (PVN) of the hypothalamus and increased glucocorticoid receptor (GR) expression in the hippocampus with improved learning and memory. Therefore, we hypothesized that we would also see a decrease in CRH expression and enhanced learning and memory in our mice. We also wanted to look at the sex differences in these changes, which has not been done before in any model.

To test our hypotheses, we conducted spatial learning and memory tasks, in addition to quantitative real-time polymerase chain reaction (RT-qPCR) analysis on PVN mRNA. While previous studies have looked at rats, this pilot study tested mice to use a transgenic CRH reporter mouse to isolate the CRH neurons in the PVN, enabling us to examine the epigenetic control of CRH after augmented maternal care.

The results showed 22% reduction in CRH expression in augmented mice (P=0.22), as well as a significant improvement in learning and memory overall in the Novel Object Recognition (NOR) test (P<0.05). Although there was no significant difference between sexes, the data indicates that the males may drive this mass effect of treatment. The Object Location Memory (OLM) test did not show any learning and memory, however, implying that the hippocampus has a lesser role in augmented maternal care.

KEYWORDS: augmented maternal care, learning and memory, transgenic mice, mouse model, CRH, early-life experience, early-life stress, child development, NOR test, OLM test, PVN

Summary of research results to be presented

Our results show that although there is not a statistically significant difference between control mice and AUG mice, there is around a 22% reduction of CRH between the two groups. The control group had a mean of 1.056 ± 0.1597. The AUG group had a mean of 0.8233 ± 0.04224. This aligns with previous studies that have shown that CRH mRNA in the PVN of handled adult rats were significantly lower than that of non-handled rats. Our statistically insignificant reduction could be due to not having a large enough population size for either group (n=5, n=6). We needed to combine males and females of both group to increase the population size. Future studies with a larger sample size of both sexes need to be done.

In both the OLM and NOR tests, we found no interaction or significant differences between sexes. In the OLM test, we found no significant effect on treatment as well. However, in the NOR test, we did find a significant mass effect on treatment overall (p=0.0086, f=8.08, DFn=1, DFd=26), with the males driving this effect. It is unclear why there would be an effect in the NOR test, but not the OLM test. This could be because the OLM test is more hippocampal dependent than the NOR test, which is more global. This could mean that the effects of learning and memory are not isolated within the hippocampus, but rather expressed in many areas of the brain overall.

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Nov 17th, 8:45 AM Nov 17th, 9:00 AM

The Effects of Augmented Maternal Care on the Learning and Memory of Mice

C161

This study investigated how augmented maternal care affects the learning and behavior of mice by looking at both molecular and behavioral changes. Early-life experiences, especially the mother-infant relationship, play a key role in determining cognitive and emotional development. While a lack of maternal care in early life can cause a long-lasting overactive stress response in the animal, enhanced maternal care has been shown to reduce the stress response, resulting in improved learning and memory.

Previous studies in rats found that augmented maternal care causes a repression of corticotropin-releasing hormone (CRH) mRNA expression in the paraventricular nucleus (PVN) of the hypothalamus and increased glucocorticoid receptor (GR) expression in the hippocampus with improved learning and memory. Therefore, we hypothesized that we would also see a decrease in CRH expression and enhanced learning and memory in our mice. We also wanted to look at the sex differences in these changes, which has not been done before in any model.

To test our hypotheses, we conducted spatial learning and memory tasks, in addition to quantitative real-time polymerase chain reaction (RT-qPCR) analysis on PVN mRNA. While previous studies have looked at rats, this pilot study tested mice to use a transgenic CRH reporter mouse to isolate the CRH neurons in the PVN, enabling us to examine the epigenetic control of CRH after augmented maternal care.

The results showed 22% reduction in CRH expression in augmented mice (P=0.22), as well as a significant improvement in learning and memory overall in the Novel Object Recognition (NOR) test (P<0.05). Although there was no significant difference between sexes, the data indicates that the males may drive this mass effect of treatment. The Object Location Memory (OLM) test did not show any learning and memory, however, implying that the hippocampus has a lesser role in augmented maternal care.

KEYWORDS: augmented maternal care, learning and memory, transgenic mice, mouse model, CRH, early-life experience, early-life stress, child development, NOR test, OLM test, PVN