Abstract
The vomeronasal system (VNS) is specialized in the detection of salient chemical cues triggering social and neuroendocrine responses. Such responses are not always stereotyped, instead, they vary depending on age, sex, and reproductive state, yet the mechanisms underlying this variability are unclear. Here, by analyzing neuronal survival in the first processing nucleus of the VNS, namely the accessory olfactory bulb (AOB), through multiple bromodeoxyuridine birthdating protocols, we show that exposure of female mice to male soiled bedding material affects the integration of newborn granule interneurons mainly after puberty. This effect is induced by urine compounds produced by mature males, as bedding soiled by younger males was ineffective. The granule cell increase induced by mature male odor exposure is not prevented by pre-pubertal ovariectomy, indicating a lesser role of circulating estrogens in this plasticity. Interestingly, the intake of adult male urine-derived cues by the female vomeronasal organ increases during puberty, suggesting a direct correlation between sensory activity and AOB neuronal plasticity. Thus, as odor exposure increases the responses of newly born cells to the experienced stimuli, the addition of new GABAergic inhibitory cells to the AOB might contribute to the shaping of vomeronasal processing of male cues after puberty. Consistently, only after puberty, female mice are capable to discriminate individual male odors through the VNS.
Highlights
Postnatal development is a critical period for the maturation of brain circuits and implies extensive interactions between external and internal factors affecting both their wiring and tuning
Our results indicate that through activity dependent regulation of accessory olfactory bulb (AOB) granule cell (GC) development, vomeronasal organ (VNO)- detected stimuli rearrange the AOB inhibitory network involved in their processing, when these cues acquire the meaning of mating signals after puberty
We previously found that exposure to male soiled bedding and male-derived urine compounds increases the survival of immature AOB GCs migrating from the subventricular zone (SVZ) in P50 female mice, but not in pre-pubertal P20 females (Oboti et al, 2011)
Summary
Postnatal development is a critical period for the maturation of brain circuits and implies extensive interactions between external and internal factors affecting both their wiring and tuning. At puberty chemical signaling begins to be used to advertise sexual receptivity and to assess both the quality and readiness of mating partners (Moncho-Bogani et al, 2002; Ramm et al, 2008) These two aspects of sexual maturation – the internal physiology and the sensitivity to environmental cues – obviously interact, and, through the vomeronasal system (VNS), chemical stimuli can affect both the development (Vandenbergh, 1967, 1974; Colby and Vandenbergh, 1974; Flanagan et al, 2011; Oboti et al, 2014) and the adult display (Haga et al, 2010; Roberts et al, 2010; Ferrero et al, 2013; Oboti et al, 2014) of female reproductive behaviors
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