Fig. 8. NMDA receptor blockade equally affects pre- and postsynaptic specializations on RGC axon and tectal neuron dendritic arbors. The effects of altering NMDAR transmission in the optic tectum on PSD95-GFP labeled postsynaptic specializations in tectal neuron dendritic arbors is compared with the effects of the same treatment on GFP-synaptobrevin-labeled presynaptic specializations on RGC axon arbors (see Hu et al., 2005). PSD95-GFP puncta and dendrite branch number in tadpoles that received a single tectal injection of APV is shown as the percent change from their initial value at the time of treatment. (A) APV significantly decreased the number of PSD95-GFP puncta compared with control 2 hours after treatment, an effect that was maintained for 24 hours. (B) A more dramatic decrease in GFP-synaptobrevin cluster number was observed 2 hours after APV treatment, with a peak cumulative effect occurring after 4 hours [adapted from Hu et al. (Hu et al., 2005)]. (C) Dendritic arbor complexity, expressed as the increase in total branch number per dendritic terminal, is affected by the APV treatment by 24 hours only. (D) Similar to dendrite branch number, the APV treatment had a significant effect on RGC axon branch number by 24 hours only [adapted, with permission, from Hu et al. (Hu et al., 2005)]. Bars indicate mean±s.e.m. For tectal neurons, n=5 in control and n=9 in APV-treated tadpoles. For RGC axons, n=14 in control and n=10 in APV-treated tadpoles. ^*P0.05; ^**P0.005 compared with control.