Hippocampal neuronal morphology and spine density in a seasonally reproducing rodent, Richardson's ground squirrel (Urocitellus richardsonii)

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Brinkman, Benjamin
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Neuroscience
Both sex and reproductive status can alter the anatomy of brain regions within individuals. In mammals, these changes can be large in seasonally breeding species, but the extent to which fluctuations in brain region sizes are driven by neuron morphology has remained untested. I tested the hypothesis that sex-seasonal differences in hippocampus size are due, in part, to changes in neuronal morphology and spine density. Through analyzing Golgi-stained tissue from wild caught Richardson’s ground squirrels (Urocitellus richardsonii), I found that season affects spine density in hippocampal neurons. In pyramidal cells, non-breeding squirrels had higher spine densities, but in granule cells non-breeding squirrels had lower spine densities. These seasonal effects on neuronal spine density likely reflect photoperiod, seasonal changes in stress, and activity levels in similar ways to studies of lab rodents. My results provide new insights into seasonal neuroplasticity in mammals and how it relates to their behaviour and environment.
Animal behavior , Golgi apparatus , Hippocampus (Brain) , Neuroanatomy , Richardson's ground squirrel , Sexual behavior in animals