Immature olfactory sensory neurons provide complementary input in the healthy olfactory system

Adult neurogenesis of olfactory sensory neurons (OSNs) in the rodent olfactory system provides the unique opportunity to understand how new neurons functionally integrate into existing circuitry and contribute to behaviors. Immature OSNs express odorant receptors (ORs), form dendritic knobs with short cilia, and project their axons into the olfactory bulb (OB) where they form functional synapses. Furthermore, immature OSNs respond selectively to odorants and exhibit graded responses in a higher concentration range than mature OSNs, suggesting that they provide a distinct odor input stream. Finally, in mice that lack mature OSNs, sensory input from immature OSNs is sufficient to mediate odor detection and discrimination behavior. What remains unknown, however, is how these immature OSNs contribute to odor-guided behavior in the healthy, intact olfactory system. Here we show, using male and female mice, that chemogenetically silencing immature OSNs impairs odor detection ability without affecting their odor discrimination ability. Furthermore, immature OSN silencing reduces the amplitude of odor-evoked dendritic calcium responses in OB neurons in vivo. Together, these findings suggest that immature OSNs provide distinct odor input that complements mature OSN input to contribute to odor-guided behaviors in the healthy, intact olfactory system.