La maternità influenza significativamente neuroni immaturi e immunoreattivi per la doublecortina nel sistema olfattivo delle femmine di topo.

Adult neurogenesis occurs in the olfactory system in macrosmatic species such as mice. In this system, immature neurons are continuously generated in the olfactory bulb (OB) during adulthood, whereas in the piriform cortex (Pir), they are generated during embryonic development and slowly mature as the animal ages. In the olfactory tubercle (OT), immature cells’ origin and possible proliferative activity have not been investigated deeply. The process of neurogenesis is hypothesised to play a significant role in olfactory learning. Moreover, changes in neurogenesis due to motherhood have been reported in the subventricular zone (SVZ) and olfactory bulb (OB). Since pup recognition in mice largely relies on olfactory cues, we hypothesised that pregnancy and/or lactation would alter the density of immature neurons and their proliferative activity in these areas. To test this hypothesis, we used double immunofluorescence to assess the expression of doublecortin (DCX), a marker of immature neurons, and Ki67, a marker of proliferation, in the olfactory bulb (OB), the olfactory tubercle (OT) and the piriform cortex (Pir) of virgin vs. pregnant (Experiment 1) and pup-sensitised virgins vs. lactating dams (Experiment 2). Our data revealed a trend towards an increase in DCX cells in the OB of pregnant females as compared to virgins, but no significant differences in other areas. We found Ki67-immunoreactivity in the OT in all the groups, suggesting continuous adult proliferation of immature neurons, albeit unaffected by pregnancy or lactation. Furthermore, in the Pir, our results suggest that lactation, but not pregnancy alone, accelerates the maturation of DCX-ir cells since complex DCX-ir cells are fewer and significantly smaller in lactating dams. Since pregnancy alone did not seem to affect this niche, it is tempting to speculate that the pup-caring after a certain hormonal set-up occurring during pregnancy may induce a process of differentiation, possibly related to olfactory recognition of the litters.