RESULTS
Abx Treatment Decreases Adult Hippocampal
Neurogenesis
We started by treating adult animals with broad-spectrum Abxs
for 7 weeks. In a previous study we have shown that application
of these Abxs severely depleted the intestinal microbiota of mice
(Heimesaat et al., 2006). To determine the phenotype of the
proliferating cells in the hippocampus, we stained with antibodies
against NeuN (which labels mature neurons) and doublecortin
(Dcx, which labels the majority of transient proliferating
mitotic neuronal progenitor cells [NPCs]; Figures 1A and 1B).
The progenitor cells expressing Dcx represent the most plastic
population of progenitors. Moreover, the commitment to the
neuronal lineage starts with the expression of Dcx (Kempermann
et al., 2004, 2015). We analyzed hippocampal sections by immunofluorescence
and detected that the number of BrdU-positive
cells in the SGZ of the DG was significantly lower in the brains
of Abx-treated animals (387 ± 60; Figure 1C, light blue bar)
compared to naive ones (592 ± 48; Figure 1C, light gray bar).
This effect was apparent in both neuronal progenitors
(BrdU/Dcx/NeuN) and mature neurons (BrdU/NeuN). These
data suggest that Abx treatment has a long-lasting effect on
neurogenesis.