Excitable Axonal Domains Adapt to Sensory Deprivation in the Olfactory System

The axon initial segment (AIS), nodes of Ranvier, and the oligodendrocyte-derived myelin sheath have significant influence on the firing patterns of neurons and the faithful, coordinated transmission of action potentials (APs) to downstream brain regions. In the olfactory bulb (OB), olfactory discrimination tasks lead to adaptive changes in cell firing patterns, and the output signals must reliably travel large distances to other brain regions along highly myelinated tracts. Whether myelinated axons adapt to facilitate olfactory sensory processing is unknown. Here, we investigate the morphology and physiology of mitral cell (MC) axons in the olfactory system of adult male and female mice and show that unilateral sensory deprivation causes system-wide adaptations in axonal morphology and myelin thickness. MC spiking patterns and APs also adapted to sensory deprivation. Strikingly, myelination and MC physiology were altered on both the deprived and nondeprived sides, indicating system level adaptations to reduced sensory input. Our work demonstrates a previously unstudied mechanism of plasticity in the olfactory system.