Figure 2.
Activity-induced fusion of BDNF-containing vesicles in axon and dendrite. A, B, a, Wide-field fluorescence microscopic images of BDNF puncta at the axon (A) and dendrite (B) of cultured hippocampal neurons expressing BDNF–pHluorin. Insets, Magnified views of BDNF–pHluorin puncta in boxed areas at 1 s before and 1 and 200 s after field stimulation (at 10 Hz for 300 pulses). Scale bar, 20 μm. b, Sample traces depict the fluorescence change (ΔF) with time at individual puncta at the axon (A) and dendrite (B). Numbers refer to the corresponding numbered puncta shown in the images above. c, Fluorescence changes normalized by the basal fluorescence (F0) and the average below traces represent the mean ± SEM pHluorin fluorescence change at the axon (A; n = 594 puncta, 16 cells) and dendrite (B; n = 300 puncta, 7 cells). No Stim, No field stimulation applied, showing insignificant bleaching over the 4 min recording period. C, D, TIRF microscopic images and pHluorin fluorescence changes at axon and dendrite. a, Images of BDNF–pHluorin puncta at 1 s before and 1 and 40 s after field stimulation. b, c, Same as in A and B, except that the fluorescence changes (ΔF) were monitored with TIRF microscopy.