Astrocytic volume fluctuates in the hippocampal CA1 region across the estrous cycle.

The number of dendritic spine synapses in the hippocampal CA1 stratum radiatum fluctuates across the rat estrous cycle, being high on proestrus and low on estrus [20]. We hypothesized that the volume occupied by astrocytic processes changes in a complementary manner. The volume fraction of astrocytic processes was determined stereologically in CA1 s. radiatum and s. lacunosum-moleculare of cycling female rats. Consistent with our hypothesis, the volume fraction was significantly lower on the afternoon of proestrus than on the afternoon of estrus in both laminae.