Fig. 1

Long lasting changes in dendritic spine morphology induced by cLTP in vitro. (a-d) Example traces and mean (+SEM) mEPSC amplitude (b), frequency (c), and decay time (d) for cultured rat hippocampal neurons recorded after treatment with glycine-based cLTP (400 μM) stimulus or HBS alone as a control (n = 7 recordings in each condition). Glycine cLTP induces a strong increase in the strength of excitatory inputs in culture. (e) Example images of dendritic spines from hippocampal neurons expressing eGFP in dissociated culture under conditions of cLTP (glycine 400 μM) or HBS control. cLTP induces robust increases in dendritic spine head width. Scale bar = 2.5 μm in upper panel 1 μm in enlarged close up image. (f-g) Cumulative probability distributions of change in spine head diameter quantified as percent of baseline value for all spines imaged under conditions of cLTP (g, n = 1538 spines across 20 cells) or HBS alone (f, n = 1320 spines across 21 cells) at time-points 5, 15, 25, 35, and 45 m post stimulation. Glycine treatment elicits a time-dependent expansion of dendritic spine heads, * denotes significant difference in a given population from the distribution obtained in the proceeding timepoint via ks test. (h) Scatter plot comparing raw values of head diameter for all spines imaged before vs 45 m after treatment with 400 μM glycine during the cLTP protocol. Black symbols denote spines with head diameter increases over 25%, while white symbols mark spines that shrink by 25%. Gray symbols along the line of equality indicate spines with less extreme alterations. Bar graph on right hand side represents distribution of these groups (black = increase, white = decrease, gray = no change) as percent of total. (i) Comparison of pre and 45 m post stimulation values for spine length, as reported for the same set of cells in (h). (j) Timecourse of changes in spine length (represented as % of baseline values). Degree of length change was not significantly different between HBS treated controls and the glycine cLTP groups when assessed 45 m post stimulation. (k) Scatter plot of individual changes in protrusion length (pre vs 45 m post glycine stimulation) vs changes in head diameter for the same group of spines