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

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 in vivo twophoton imaging, we monitored longitudinally the dendritic morphogenesis, odor-evoked responsiveness, endogenous Ca2+ signaling and survival/death of adult-born juxtaglomerular neurons (JGNs). We found that JGN maturation is accompanied by a significant reduction in dendritic complexity, with surviving and subsequently eliminated cells showing similar degrees of reduction and dendritic remodeling. Moreover, ~63% of subsequently eliminated adult-born JGNs acquired odor-responsiveness before death, with amplitudes and time courses of odor-evoked responses similar to those recorded in the surviving cells. We observed, however, a significant long-lasting enhancement of the endogenous Ca2+ signaling in subsequently eliminated JGNs, visible already 6 days before death. These findings identify the ongoing endogenous Ca2+ signaling as a key predictor of the adult-born JGN’s fate