PBM alleviates depression and anxiety like behaviors in mice: insight from local field potential

Depression involves abnormal neural oscillations. Photobiomodulation (PBM) modulates such oscillations but lacks behavioral electrophysiological mechanistic studies. We explored PBM's effects on hippocampal CA1 oscillations and phase-amplitude coupling (PAC) in a depression model.

Male C57BL/6J mice were randomly divided into saline, LPS (2 mg/kg i.p.), and LPS + PBM groups (n = 10/group for behavioral tests, n = 8/group for electrophysiology). LPS groups received lipopolysaccharide to induce neuroinflammation. The LPS + PBM group underwent 810 nm PBM (20 mW/cm², 12 min/day × 4 days) starting day 4 post-injection. Anxiety- and depression-like behaviors were assessed via open field, elevated plus-maze, and tail suspension tests. Wireless electrophysiology recorded CA1 local field potentials (LFP) during rest and behaviors. Oscillations and PAC were analyzed. Data are presented as mean ± SD; group differences were evaluated by one-way ANOVA with Bonferroni post-hoc correction and ɳ² effect sizes, with two-tailed p < 0.05 taken as statistically significant.

PBM (20 mW/cm²) alleviated LPS-induced anxiety and depressive behaviors. Electrophysiologically, PBM restored resting-state δ power (LPS + PBM: 0.0499 ± 0.0282, LPS: 0.1491 ± 0.0887; p < 0.01) and enhanced δ-γ coupling (LPS + PBM: 2.049 ± 0.447, LPS: 0.230 ± 0.298; p < 0.05). During anxiety tasks, PBM suppressed γ power (LPS + PBM: 0.3709 ± 0.1569, LPS: 0.5165 ± 0.06896; p < 0.05) and strengthened δ-γ PAC (LPS + PBM: 0.741 ± 0.508 vs. LPS: 0.217 ± 0.218, p < 0.05). In depression tests, PBM normalized δ power (LPS + PBM: 0.0261 ± 0.0182, LPS: 0.1315 ± 0.0619; p < 0.001) and reduced γ power (LPS + PBM: 0.2848 ± 0.0921, LPS: 0.4067 ± 0.0892; p < 0.05). No significant PAC changes was observed during depression tasks.

PBM therapy ameliorates LPS-induced depression and anxiety behaviors while normalizing hippocampal CA1 oscillations and cross-frequency coupling. Its effects are state-dependent, modulating distinct frequency bands and PAC across rest and behavioral contexts, revealing potential electrophysiological therapeutic mechanisms.