Enhanced endogenous activity predicts elimination of adult-born neurons in the mouse olfactory bulb

Abstract

Adult-born cells, arriving daily into the rodent olfactory bulb, either integrate into the neural circuitry or get eliminated. Whether these two populations differ in their morphological or functional properties remains, however, unclear. Using longitudinal in vivo two-photon imaging, we monitored dendritic morphogenesis, odor-evoked responsiveness, endogenous Ca2+ signaling, and survival/death of adult-born juxtaglomerular neurons (abJGNs). We found that maturation of abJGNs is accompanied by a significant reduction in dendritic complexity, with surviving and subsequently eliminated cells showing similar degrees of dendritic remodeling. Surprisingly, 63% of eliminated abJGNs acquired odor-responsiveness before death, with amplitudes and time courses of odor-evoked responses similar to those recorded in surviving cells. We observed, however, a significant long-lasting enhancement of endogenous Ca2+ signaling in subsequently eliminated abJGNs, visible already 6 days before death. These findings identify ongoing endogenous Ca2+ signaling as a key predictor of abJGNs fate.