UBC Theses and Dissertations
Adult hippocampal neurogenesis and cell activation are regulated by sex differences in spatial learning Chow, Yin Man Carmen
Adult hippocampal neurogenesis is associated with hippocampus-dependent learning and memory. Throughout the course of a new neuron’s development, it is differentially sensitive to factors that can influence its survival and subsequent functionality. Previous research shows that in male rats, spatial training that occurred 6 to 10 days after an injection of the DNA synthesis marker, bromodeoxyuridine (BrdU), increased cell survival, but no change was observed in animals trained on days 1 to 5 or 11 to 15 and perfused 16 days after BrdU injection (Epp et al., 2007). Because sex differences favouring males in spatial cognition and in hippocampal neurogenesis have been reported, it is unclear whether spatial learning would influence hippocampal neurogenesis in the same way in males and females. Therefore, this study aimed to compare sex differences in hippocampal neurogenesis relative to training in a spatial task. Male and female rats were exposed to training in the spatial or cued version of the Morris Water Maze 6 to 10 days after one injection of BrdU (200mg/kg). Twenty days following BrdU injection, all animals were given a 30-second probe trial and perfused. Males showed better performance in the spatial task, but not cue task, than females. Spatial learning increased the density of BrdU-labeled cells relative to cue training only in males, but both males and females showed greater cell activation (BrdU co-labeled with immediate early gene product zif268) after spatial training compared to cue training. Furthermore, performance during spatial training and testing were positively correlated with cell activation in females but not males. This study shows that while spatial learning differentially regulates hippocampal neurogenesis in males and females, the activity of new neurons in response to spatial memory is similar. These findings highlight the importance of sex on neural plasticity and cognition.
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