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Dendritic stability in the adult olfactory bulb


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.

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Figure 1: Two-photon imaging of M/T cells and their apical dendrites in the olfactory bulb of a YFP-G mouse.
Figure 2: Morphological analysis of M/T cell apical dendrites.
Figure 3: Dendritic stability of M/T cell apical dendrites in adult mice.
Figure 4: Dendritic stability of M/T cell apical dendrites following odor enrichment.
Figure 5: Increased activity destabilizes M/T cell apical dendrites.
Figure 6: Intrinsic signal imaging following learning of an olfactory discrimination task.
Figure 7: Dendritic stability following learning of an olfactory discrimination task.


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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.

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Correspondence to Adi Mizrahi.

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Supplementary information

Supplementary Fig. 1.

Quantitative analysis of a mitral cell apical dendrite. (a) Projection image of a single apical tuft of a mitral cell transfected with Sindbis-GFP in the olfactory bulb of an adult mouse. (b) Reconstruction of the complete dendritic tree shown in a. Scale bar: 25μm. (c) Two-dimensional dendrogram of the reconstructed apical dendritic tuft shown in a. (PDF 323 kb)

Supplementary Fig. 2.

Dendritic changes are distributed throughout the glomerular depth. Frequency of the position (glomerular depth) of the dendritic changes (% of total sprouting and pruning events) pooled from all control experiments. The low percent of changes observed in the first 10 μm reflects the less dense dendritic labeling in this region of the glomerulus. (PDF 44 kb)

Supplementary Fig. 3.

Quantitative morphometric comparison (of the number of branching points, total dendritic length and total surface area) between the single complete dendritic tuft (shown in Supplementary Fig. 1) and the dendritic reconstructions from the two-photon experiments (averages ± SEM). In the two-photon experiments we sampled the equivalent of 85%, 50% and 35% of the total number of branches (a), length (b) and surface area (c), respectively, of a single complete M/T dendritic tuft. The relative higher value for the number of branching points probably reflects that our sample mainly contains distal higher order branches where a higher frequency of branching is evident (see dendrogram in Supplementary Fig. 1c). (PDF 54 kb)

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Mizrahi, A., Katz, L. Dendritic stability in the adult olfactory bulb. Nat Neurosci 6, 1201–1207 (2003).

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