Fig. 2

SHPs have shortened lifetimes in SP-KO hippocampal slice cultures. a Examples of small regions of dendrites from WT (top two rows) and SP-KO (bottom two rows) exposed to 60 min of either control or TTX-containing medium (as indicated). Arrows denote SHPs. Time is in minutes in top-left corner, and 10 min was the starting time point. Scale bar, 2 μm. b Time course of SHP formation in WT (black symbols) or SP-KO (gray symbols) slices exposed to control solution (open symbols) or TTX (closed symbols). Although SP-KO dendritic spines can form SHPs, they are unstable and retract, while WT spines can form protrusions that persist. n = 6 slices, ~150 μm of dendrite per treatment. *P < 0.05, two-tailed, one-way ANOVA with Dunnett’s test compared with WT control, SP-KO control and SP-KO TTX treated. c Quantification of mean lifetime of all SHPs (from both of control or TTX experiments) from WT and SP-KO dendrites. SHPs had a mean lifetime of 16.32 ± 3.40 min in WT (n = 25 SHPs from 12 slices), compared to 7.15 ± 1.48 min from SP-KO (n = 47 SHPs from 12 slices). Gray circles are individual lifetimes of SHPs, and black circles are mean lifetimes ± SEMs. *P < 0.05, Mann-Whitney. d SHPs sorted by lifetime in WT (black framed cityscape) and SP-KO (gray bars). e Cumulative distribution of all SHP lifetimes from WT (black line) and SP-KO (gray line) slices