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UBC Theses and Dissertations

The role of reproductive experience on hippocampus-dependent spatial memory, adult hippocampal neurogenesis, and corticosterone in the rat dam Pawluski, Jodi Lynn

Abstract

Pregnancy and the postpartum period have remarkable effects on cognition in the mother. Interestingly, motherhood results in enhanced spatial memory in the rodent. This thesis aimed to determine the role of reproductive experience (number of times pregnant and maternal) on enhanced hippocampus-dependent spatial memory in the mother, as well as the neural and hormonal correlates of this effect. Chapter 2 demonstrates that reproductive experience differentially affects spatial memory performance at the time of weaning resulting in enhanced memory performance in primiparous rats compared to nulliparous rats, with a trend toward enhanced memory performance in multiparous compared to nulliparous rats. Chapter 3 demonstrates that the enhanced spatial memory in primiparous rats persists after the time of weaning and is not due to pregnancy or pup-exposure alone. Chapter 4 demonstrates that reproductive experience results in decreased cell proliferation and cell survival in the dentate gyrus during the postpartum in primiparous rats and multiparous rats. Furthermore primiparous rats had decreased levels of cell survival compared to multiparous rats, and pup-exposed nulliparous females had increased levels of cell proliferation and cell death after brief pup-exposure. Chapter 5 demonstrates that primiparous rats have significantly elevated total corticosterone in the early postpartum period as well as lower CBG during the postpartum period. Thus, taken together the results from the experiments suggest that the enhancement in hippocampus-dependent spatial memory seen in primiparous and multiparous rats is coincident with reduced hippocampal neurogenesis, increased corticosterone, and decreased corticosteroid binding globulin (CBG) during the postpartum period in the mother. These findings demonstrate that motherhood is a time of marked neural plasticity in the hippocampus, an area of the brain not traditionally associated with motherhood.

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