Acupuncture alleviates CSDS-induced depressive-like behaviors by modulating synaptic plasticity in vCA1

Abstract

Acupuncture (Acu) has been clinically validated as an effective treatment for depression. However, the underlying mechanism of Acu treatment's antidepressant effect remains unclear. Methods: We investigate the antidepressant effects of Acu treatment at the LR3 point in mice subjected to chronic social defeat stress (CSDS). GCaMP6m-based fiber-optic photometry was employed in the ventral CA1 (vCA1) regions for the first time to monitor Ca²⁺ transients in vivo during behavioral testing. Electrophysiological recordings were used to detect the activity and synaptic function of pyramidal neurons. Golgi staining was performed to measure the density of dendritic spines in the vCA1. Western blot analysis was conducted to quantify the expression levels of phosphorylated CaMKIIα, AMPA receptor protein (GluA1, GluA2), and brain-derived neurotrophic factor (BDNF) in the hippocampus. Results: Our findings indicated that Acu treatment significantly alleviated emotional deficits and restored the activity of pyramidal neurons, which were suppressed by CSDS. Acu treatment also reversed the decrease in spontaneous excitatory postsynaptic currents (sEPSCs), thereby enhancing glutamatergic transmission. Moreover, Acu treatment improved synaptic plasticity, as evidenced by increased dendritic spine density and restored expression levels of phosphorylated CaMKIIα, GluA1, GluA2 and BDNF. Conclusion: Collectively, these findings suggest that Acu treatment alleviates depressive-like behaviors induced by CSDS and enhances synaptic function in the vCA1 region, potentially through mechanisms involving increased AMPAR trafficking and BDNF expression.

Keywords: LR3; acupuncture; depression; fiber photometry; synaptic plasticity.

Figure 1

Acu Treatment Reverses CSDS-induced behavioral disorders. (A) A paradigm for behavioral modeling of CSDS in mice; schematic representation of therapeutic points and experimental protocol for behavioral testing. (B) Coefficient of sucrose preference in the SPT. (C) The duration of immobility in the TST for 5 min. (D) The duration of immobility in the FST for 5 min. (E) Trace diagrams for SIT. (F) Social Interaction Ratio for the SIT. (G) Time spent in social interactions “No target” and “Target” for SIT. (H) Representative locomotion traces in OFT. (I) The total distance travelled in OFT. (J) Persistence time in the central area of OFT. n = 10 mice/group. Panel G, two-way ANOVA with Tukey's multiple comparisons test, Remaining panels, one-way ANOVA with Tukey's multiple comparisons test. Data are represented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001. n.s., no significant difference.

Figure 2

Acu treatment enhances the pyramidal neuronal activity of vCA1. (A) Experimental diagram of c-Fos staining. (B) Location of selected sagittal slices of the ventral hippocampus in the mouse brain atlas. (C) The c-Fos expression in vCA1 area. Scale bar, 50 μm. (D) Statistical results of c-Fos positive cells (one-way ANOVA with Tukey's multiple comparisons test). n = 4 mice/group. (E) Example of membrane-clamp recording of vCA1 pyramidal neurons in whole-cell configuration. (F) Example voltage traces evoked by 190 pA inward current injection in vCA1- pyramidal neurons. Scale bars, 400 ms, 20 mV. (G) Summarized AP data recorded from vCA1-pyramidal neurons; 0~230 pA, 20 pA steps, 1 s duration. (H) Spontaneous firing rates. n = 10 neurons from 3 mice, respectively. One-way ANOVA with Tukey's multiple comparisons test; Data are represented as the mean ± SEM. **P < 0.01, ***P < 0.001.

Figure 3

Acu treatment enhances vCA1 excitatory neuron activity during TST and NSFT. (A) Timeline of vCA1 calcium signal detection. (B) Representative image showing AAV delivered GCaMP6m expression and optical fiber placement in the vCA1; scale bar: 500 μm (main), 50 μm (inset, 20x). (C) Heatmap of Ca²⁺ signals from CaMKIIα-positive neurons aligned to the onset of struggling. (n = 35, 75, 50 trials) (D) Peri-event plots of Ca²⁺ signals changes from CaMKIIα-positive neurons during Control (yellow), CSCS (red) and Acu (blue) epochs. (E) The area under the curve of calcium activity of vCA1 CaMKIIα-positive neurons (Ordinary one-way ANOVA with Dunnett's multiple comparisons test). (F) Quantification of TST-induced peak for Control, CSDS and Acu mice (RM one-way ANOVA with Dunnett's multiple comparisons test). (G) Heatmap of Ca²⁺ signals from CaMKIIa-positive neurons aligned to the onset of Sniffing food. (n = 26, 54, 25 trials) (H) Peri-event plots of Ca²⁺ signals changes from CaMKIIα-positive neurons during Control (yellow), CSCS (red) and Acu (blue) epochs. (I) The area under the curve of calcium activity of vCA1 CaMKIIα-positive neurons (Ordinary one-way ANOVA with Dunnett's multiple comparisons test). (J) Quantification of NSFT-induced peak for Control, CSDS and Acu mice (RM one-way ANOVA with Dunnett's multiple comparisons test). n = 5 mice/group. Solid lines indicate mean and shaded areas indicate SEM. *P < 0.05, **P < 0.01, ***P < 0.001.

Figure 4

Acu treatment increases excitatory transmission in vCA1 pyramidal neurons. (A) Representative traces of sEPSCs recorded from vCA1 pyramidal neurons. (B, C) Average sEPSCs amplitude (B) and frequency (C) in Control (yellow), CSDS (red) and Acu (blue) groups, n = 10 cells from 3 mice/group (For all figures: Kolmogorov-Smirnov test). (D) Representative traces of AMPAR EPSCs recorded at -70 mV and dual component EPSC at +40 mV. (E) AMPA/NMDA ratio is increased by Acu treatment. n = 10 cells from 3 mice/group (For all figures: one-way ANOVA with Tukey's multiple comparisons test). (F) Correlations between sEPSCs frequency in vCA1 pyramidal neurons and TST in control, CSDS and Acu mice, respectively. (G) Correlations between sEPSCs amplitude in vCA1 pyramidal neurons and TST in control, CSDS and Acu mice, respectively. Data are represented as the mean ± SEM. *P < 0.05, **P < 0.01.

Figure 5

Acu treatment restores synaptic plasticity and BDNF expression impaired by CSDS in the hippocampus. (A) The images of apical dendrites in the vCA1 by Golgi stain. Scale bar, 2 μm. (B) Quantification of spine numbers, n = 25 dendrites from 5 mice/group (Ordinary one-way ANOVA with Dunnett's multiple comparisons test). (C) Correlations between spine density in vCA1 pyramidal neurons and FST. (D) Representative immunoblots of p-CaMKII, p-GluA1 and BDNF in hippocampal extracts. (E-G) Quantification of p-CaMKII (E), p-GluA1 (F) and BDNF (G), n = 5 mice/group (Ordinary one-way ANOVA with Dunnett's multiple comparisons test). (H-J) Correlations between p-CaMKII (H), p-GluA1 (I) and BDNF (J) protein level in hippocampus and SPT. Data are represented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001. n.s., no significant difference.

Figure 6

Schematic summary of present study. CSDS induces depression-like behaviors in adult mice, accompanied by reduced intrinsic excitability of vCA1 pyramidal neurons and downregulation of synaptic plasticity. Acupuncture (Acu) treatment ameliorates these deficits, and its mechanism may be related to enhancing the membrane trafficking of AMPAR and upregulating the expression of BDNF.