Synaptic activity is neither altered by different dendritic PRG3 levels nor changes in PRG3 distribution. (A) Image of a representative hippocampal neuron shows an evenly distributed PRG3 signal (anti-GFP) when overexpressed. Scale bar: 75 μm. (B) Representative current recordings from cultured hippocampal neurons either overexpressing GFP (native PRG3 level; control) or overexpressing a GFP-mPRG3 construct. mEPSCs were pharmacologically isolated (see Methods) and recorded at −70 mV. (C) Box plots of mEPSC frequency and mean amplitude box plots, as well as distribution of individual values. (Left) mEPSC frequency measured for each neuron is summarized and displayed as a statistical plot. Individual values are shown to the right of each box. No difference was observed (Mann–Whitney U test, p = 0.16, n = 12). (Right) For each neuron all mEPSC amplitudes were averaged. The mean amplitudes for each neuron are shown for either GFP (control) or GFP-mPRG3-overexpressing neurons. No difference was observed, regardless of the PRG3 level (unpaired t-test, p = 0.27, n = 12). (D) Immunocytochemistry analyses of PRG3 expression distribution on tau1 and MAP-2 positive structure with and without activity blockers. This treatment from DIV 4 to DIV 14 in culture did not change in the shift of PRG3 from dendrites to axons. Scale bar: 5 μm.