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Fig. 7. Dendrite branch and postsynaptic specialization dynamics in individual
tectal neuron dendritic arbors. Time-lapse confocal imaging of neurons
expressing DsRed2 and PSD95-GFP illustrates postsynaptic site and dendritic
branch dynamics. (A) Image reconstructions of a tectal neuron
illustrates the localization and distribution of PSD95-GFP puncta (yellow)
within specific regions of the arborizing, DsRed-labeled dendritic arbors
(red). (B,C) Magnified regions of two dendritic arbors show that
transient (arrowhead) and stable (arrows) branches appear at arbor sites where
PSD95-GFP puncta localize. A significant number of branch points
(72.3±2.3%) contained PSD95-GFP puncta (not shown graphically).
(D,E) Detailed analysis of number and distribution of
PSD95-GFP-labeled puncta per arbor illustrates the relationship between
synapse and dendritic branch dynamics. The number of branches and PSD95-GFP
puncta that remained from one 2-hour observation interval to the next (stable
puncta), and the number of new branches and PSD95-GFP puncta added between
observation intervals was calculated and normalized for each time interval to
obtain a dynamic measure of branch and synapse addition and stabilization over
time. (D) An average of 70.1±3.9% branches were stable and
34.5±5.7% branches were added at each 2-hour observation interval. (E)
Most PSD95-GFP puncta per dendritic arbor were stable; an average of
76.4±3.3% puncta remained at the same location from one observation
interval to the next and 30.8±6.0% new puncta appeared at each 2-hour
observation interval. Symbols indicate means±s.e.m.; n=5
neurons in five tadpoles.
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