Fig. 3. Anti-BDNF significantly decreases GFP-synaptobrevin cluster number and influences axon arbor complexity. Several morphological parameters illustrate the dynamic changes in GFP-synaptobrevin labeled presynaptic sites and axon arborization in control and anti-BDNF treated tadpoles followed every 2 hours for 8 hours and again at 24 hours. All parameters are expressed as percent change from their initial value at the time of treatment. (A) Total GFP-synaptobrevin cluster number per axon terminal in control- and anti-BDNF-treated tadpoles. Anti-BDNF significantly decreases GFP-synaptobrevin cluster number versus control 4 hours after treatment. (B) The complexity of both control and anti-BDNF-treated arbors is illustrated by the net increase in total branch number per axon terminal. A significant decrease in branch number by 4 hours in anti-BDNF treated tadpoles versus control parallels the decrease in synaptic cluster number. (C,D) A measure of synapse density in both control- and anti-BDNF-treated tadpoles is provided by comparing the increase in GFP-synaptobrevin cluster number with the increase in (C) branch number or (D) total arbor length (expressed as a ratio). In controls, there is a one-to-one relationship in the increase in GFP-synaptobrevin cluster number to arbor length, while in anti-BDNF-treated tadpoles GFP-synaptobrevin cluster density is decreased to 50-60%. This difference is significant from 4 to 8 hours after treatment. Bars indicate mean±s.e.m. n=14 axon arbors in control and n=10 arbors in anti-BDNF; ^*P0.05; ^**P0.005; ^***P0.0005.