Gender and endogenous levels of estradiol do not influence adult hippocampal neurogenesis in mice

Abstract

In several species, including rat and vole, the proliferation of new neurons in the adult dentate gyrus (DG) subgranular zone (SGZ) is influenced by both gender and endogenous levels of the gonadotropic steroid hormone estradiol. However, little is known about how adult neurogenesis is regulated by these factors in the mouse. We report here that adult C57BL/6 mice do not have gender differences in hippocampal proliferation or neurogenesis. In addition, the production of new SGZ cells in female mice was not influenced by estrous cycle or after ovariectomy, suggesting that fluctuations in endogenous estradiol levels do not alter adult neurogenesis in the mouse. Both male and female mice had a greater number of BrdU-immunoreactive SGZ cells following chronic treatment with fluoxetine. This demonstrates a parallel proliferation response in both genders, and opens avenues for addressing the neurogenesis hypothesis of depression in female rodents. These findings underscore a distinct regulation of adult neurogenesis in mice vs. other rodents, and are discussed in regard to their implications for the study of adult hippocampal neurogenesis.

Active Dentate Granule Cells Encode Experience to Promote the Addition of Adult-Born Hippocampal Neurons

“…Moreover, the active DGC ensemble exhibits location specific firing and this placecoding ensemble undergoes remapping in a distinct context. This is consistent with the role of the DG in pattern separation (Leutgeb et al, 2007) and suggests a potential role of active DGCs in spatial learning and memory.…”

“…Novel environmental exploration activates various brain circuits and increases synaptic plasticity, particularly in the trisynaptic circuit, which processes spatial information for memory encoding and retrieval (Abraham et al, 2002;Leutgeb et al, 2005;Kee et al, 2007;Li et al, 2013). In this circuit, integration of new hippocampal neurons has been widely acknowledged to provide an additional layer of structural and functional plasticity (Jessberger andSahay et al, 2011b;Cameron and Glover, 2015).…”

“…Each dataset included both male and female animals because previous work has shown no detectable sex differences in adult hippocampal neurogenesis (Lagace et al, 2007;Ben Abdallah et al, 2010). All mice were housed in pairs and maintained on a 12 h light/dark cycle.…”

“…We hypothesized that the enhanced DGC firing would be associated with object exploration in an Enr environment because the DG is critical for object recognition and pattern separation (Leutgeb et al, 2007;Jessberger et al, 2009). We exposed mice to Enr environments consisting of four distinct objects, the locations of which we henceforth refer to as "object zones," whereas the rest of the arena we designated as "open zones" (Fig.…”

A morphologically distinct granule cell type in the dentate gyrus of the red fox correlates with adult hippocampal neurogenesis

“…Our findings agrees with reports in laboratory (Lagace et al, 2007) and wild mice (Amrein et al, 2004a), but contrasts with findings in voles and rats, in which hormone levels can influence neurogenesis in a sex-dependent manner (Barker and Galea, 2008). The complex social structure of foxes, which is in interplay with habitat and ontogenetic factors, would require a much larger sample size to address sex or hormone dependent alterations of adult hippocampal neurogenesis.…”