Naturally occurring fluctuation in dendritic spine density on adult hippocampal pyramidal neurons

TLDR

Golgi-impregnated tissue was used to show that apical dendritic spine density in CA1 pyramidal neurons fluctuates cyclically with estradiol and progesterone levels across the estrous cycle in adult female rats. Spine density dropped by ~30% between late proestrus and late estrus, then returned to proestrus levels over several days, while CA3 pyramidal cells and dentate gyrus granule cells showed no such changes, indicating rapid, ongoing dendritic plasticity in this specific hippocampal neuron population.

Abstract

We have used Golgi-impregnated tissue to demonstrate that apical dendritic spine density in CA1 hippocampal pyramidal cells undergoes a cyclic fluctuation as estradiol and progesterone levels vary across the estrous cycle in the adult female rat. We observed a 30% decrease in apical dendritic spine density over the 24-hr period between the late proestrus and the late estrus phases of the cycle. Spine density then appears to cycle back to proestrus values over a period of several days. In contrast, no significant changes in dendritic spine density across the estrous cycle occur in CA3 pyramidal cells or dentate gyrus granule cells. These results demonstrate rapid and ongoing dendritic plasticity in a specific population of hippocampal neurons in experimentally unmanipulated animals.