This raised questions about the relative U0126 ic50 positions of these two inputs just before EO. The overall “opposing gradient” pattern of innervation was also observed before EO (Figures 3A–3G). Of the 124 Thy1 eGFP pups with both retina and cortical labeling surgeries on P9, both inputs were successfully labeled on only one P11 DOV neuron with sufficient dendritic labeling to unambiguously identify it as a DOV neuron. We found retinal axons in close contact with the proximal dendrites and dorsal

somata of this neuron, whereas cortical axons were mostly restricted to the ventral portion of the soma (Figures 3F and 3G). This apparent difference in location of the cortical and retinal axons before and after EO in young adults suggests that cortical inputs move to dendrites and displace existing retinal terminals to more distal dendritic sites during high quality pattern vision. In support of such invasive

ability, it is only after EO that corticocollicular inputs become the primary inhibitor of dorsally directed sprouting of the ipsilateral retinal projection following an early contralateral retinal lesion (Colonnese and Constantine-Paton, 2001). GFP-labeled DOV neurons at P13, 1 day after EO, have abundant dendritic protrusions and appear “hairy” (Figures 4A–4D). Densities of spines and filopodia Angiogenesis inhibitor were examined across the dendritic arbor of developing DOV neurons, with dendrites classed by caliber rank. Filopodia (length > 3 width) have been characterized as new or particularly (-)-p-Bromotetramisole Oxalate dynamic protrusions, whereas spines (length ≤ 3 width) are more likely to contain matured, stronger, or stabilized synapses (see Supplemental Experimental Procedures). These criteria were used to quantify structural changes

indicative of synaptogenesis on dually innervated DOV neurons before (P11) and 24 hr after controlled EO (P13) as well as 4 days AEO (P16) and at least 20 days AEO (adult) (Figures 4E and 4F). Dendrites of all calibers had few filopodia at P11, but rapidly developed a high density of filopodia by P13 that were eliminated by P16 (Figure 4F). These changes reached significance on the thinnest and most abundant dendrites, caliber 3 and caliber 4. Significant changes in spine density were not observed with age (one-way ANOVA, p > 0.05, calibers 2, 3, 4). Between the youngest and oldest ages studied (P11 and “Adult”), there were detectable but small mean increases in both total dendritic branch length and the complexity of arbors (Figure S3). Small increases in apical dendritic complexity and length occurred proximal, but not distal, to the soma, suggesting that maturing cells added new synaptic space proximally. We tested whether the surge in filopodia at EO required visual experience by comparing P13 littermates whose eyes were opened (EO) or closed (EC) (Figure 5A).