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.