Fig. 2

Kainic acid-induced synaptic loss and reduced dendritic morphology were reversed by PBM in cultured hippocampal neurons. A Representative images of PSD puncta analysis using the image processing algorithm showed that 850 nm PBM protected PSD puncta against kainic acid-induced PSD loss. PSD95-labeled green fluorescent puncta superimposed on MAP2 fluorescence (red) acquired before and 4 h after treatment with 150 µM kainic acid, and following 850 nm PBM 30 min after treatment with kainic acid. Confocal images were analyzed using ImageJ software. Labeled PSDs were dilated and overlaid on the MAP2 image for viewing purposes. The scale bars indicate 20 µm. Counting preceded dilation and labeling, so PSDs in close proximity were counted individually. The insets are enlarged images of the boxed region. The scale bars indicate 10 µm. B Bar graph shows significant changes in PSD puncta following treatment with 850 nm PBM in the absence (control) or presence of 150 µM kainic acid as indicated. C PSD95 of hippocampal primary cultured neurons was analyzed by western blotting with anti-PSD95 antibody. Full-length blots/gels are presented in Additional file 1: Fig. S1. In the bar graph, quantification of the normalized band intensities (ratio of PSD95 protein to β-actin) indicated that PSD95 significantly increased in the presence of 850 nm PBM. These lanes were run on the same gel but were noncontiguous. D–H Quantification of branches, total dendrite outgrowth, median process length, maximum process length, and mean process length per neuron based on MAP2 signals. Neurons in the 850 nm PBM group showed significantly longer dendrites. I Cell viability in primary hippocampal cultured neurons under control and 850 nm PBM condition groups were determined by the CCK-8 assay. 850 nm PBM increased cell viability after kainic acid-induced neuronal death. Data are expressed as the mean ± SEM; *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 relative to each control group (ANOVA with the Bonferroni test)