In many regions of the adult mammalian brain, pronounced changes in synaptic input caused by lesions or severe sensory deprivation induce marked sprouting or retraction of neuronal dendrites. In the adult olfactory bulb, adult neurogenesis produces less pronounced, but continuously ongoing synapse turnover. To test the structural stability of adult dendrites in this context, we used two-photon microscopy to image dendrites of mitral and tufted (M/T) cells over prolonged periods in adult mice. Although pharmacologically increased activity could elicit morphological changes, under natural conditions such as ongoing neurogenesis, an odor-enriched environment or olfactory-based learning, M/T cell dendrites remained highly stable. Thus, in a context of ongoing adult synaptogenesis, dendritic stability could serve as a structural scaffold to maintain the organization of local circuits.
Bibliographical noteFunding Information:
L.C.K. is an Investigator in the Howard Hughes Medical Institute. Supported by National Institutes of Health grant DC005671. We are grateful to G. Feng (Duke University Medical Center) for providing the YFP–G mice. We are grateful to members of the Katz lab for comments on the manuscript. A.M. is supported by a long-term fellowship of the Human Frontier Science Program.