Fig. 4. BDNF influences postsynaptic specializations on tectal neurons without altering dendritic arbor morphology. The effects of BDNF and anti-BDNF treatment on (A) dendrite branch number, (B) total dendritic arbor length, and (C) number and (D) density of PSD95-GFP-labeled postsynaptic specialization are expressed as percent change from their initial value at the time of treatment. (A) Total dendrite branch number was similar for tectal neurons in control, BDNF and anti-BDNF treated tadpoles at all observation time points. (B) A similar relative increase in total dendritic arbor length, a measure of dendrite branch number and the spatial extent of all branches, was observed in control and BDNF-treated tadpoles at all observation time points. By contrast, total dendritic arbor length remained close to its initial value at all observation time points after anti-BDNF treatment. (C,D) BDNF significantly increased (C) the number and (D) density of PSD95-GFP puncta per dendritic arbor 24 hours after treatment, an effect that was strengthened and maintained for 48 hours. (C,D) Anti-BDNF significantly decreased PSD95-GFP puncta number by 24 hours but did not influence puncta number per unit arbor length. Bars indicate s.e.m. n=18 neurons in control, n=16 neurons in BDNF and n=12 neurons in anti-BDNF. ^*P0.05, ^**P0.005 compared with control.