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. 2026 Oct 28;12(44):eaei2661. doi: 10.1126/sciadv.aei2661

Fig. 4. Presynaptic filopodia formation is associated with increased synchronous and reduced asynchronous neurotransmitter release.

Fig. 4.

(A) iGluSnFR3.v857 responses at individual boutons without (left) and with filopodia (right) during a 300-AP (20-Hz) stimulation train, showing stimulation period and posttrain asynchronous window. (B) TIRF imaging of representative neurons expressing iGluSnFR3.v857 enabling simultaneous detection of glutamate release and filopodia formation. Insets (yellow dashed circles) show representative boutons without (green arrow) and with filopodia (white arrow). Scale bars, 1 μm. (C) Release rate in the first second of stimulation at boutons with and without filopodia. Bars are the mean. P values, paired t test. (D) CV of release rate in the first second of stimulation. Bars are the mean. P values, paired t test. (E) Synchronous release rate across successive 1-s bins of the stimulation train at boutons with and without filopodia. Lines are the mean, and error bars are SEM. P values, repeated-measures ANOVA with Sidak’s test. (F) Late release rate (mean across bins 12 to 15 s) at boutons with and without filopodia, compared within individual neurons. Bars are the mean. P values, paired t test. (G) Posttrain asynchronous iGluSnFR3.v857 event frequency at boutons with and without filopodia. Bars are the mean. P values, paired t test. (H) Histogram of the T-max relative to stimulus onset. (I) Correlation between release rate at the final second of the train and posttrain asynchronous event frequency across neurons. (J) Correlation between late release rate (bins 12 to 15 s) and posttrain asynchronous event frequency across neurons.