Increased dendritic length in CA1 and CA3 hippocampal neurons during the metestrus phase in Wistar rats.

Studies have shown that changes in ovarian hormone concentrations promote natural fluctuations in the density of dendritic spines of hippocampal neurons in female Sprague-Dawley rats, without changes in dendritic length, throughout the estrous cycle. However, it is still unknown whether these fluctuations are present in other rat strains. Due to our interest in Wistar rats, the objective of the present study was to determine if there is natural dendritic remodeling in the female Wistar rat throughout the estrous cycle. This study analyzed the dendritic arborization of pyramidal neurons CA1 and CA3 of the dorsal hippocampus in each phase of the estrous cycle. We used the Golgi-Cox staining method and Sholl analysis to evaluate the dendritic length and density of dendritic spines. Our results showed that the dendritic length of the basilar and apical trees of CA1 neurons was longer in the metestrus phase. In CA3 neurons, only the apical dendritic trees showed longer dendritic length during metestrus. There was no variation in the density of dendritic spines in relation to any of the phases of the estrous cycle. Taken together, these results indicated that pyramidal neurons of the CA1 and CA3 regions of the dorsal hippocampus in the Wistar rat exhibited changes in dendritic length in the metestrus phase of the estrous cycle. Together, these data are important when considering the use of these organisms in behavioral studies.