Electroacupuncture improves synaptic plasticity mediated by Glu/GABA balance in the medial prefrontal cortex of mice with perimenopausal depression

To observe the effect of electroacupuncture (EA) on depressive-like behaviors and sex hormone levels in perimenopausal depression mice, so as to explore its regulatory role in the glutamate (Glu)/γ-aminobutyric acid (GABA) balance in the medial prefrontal cortex (mPFC) and its impact on the structural and functional plasticity of mPFC synapses.

Female C57BL/6J mice were randomly divided into control, model, estradiol (E₂), and EA groups, with 14 mice in each group. The perimenopausal depression model was established using vinylcyclohexene dioxide (VCD) combined with chronic unpredictable mild stress (CUMS). Mice in the EA group received EA at “Shenshu” (BL23), “Sanyinjiao” (SP6), “Baihui” (GV20), and “Yintang” (GV24⁺) for 30 min. The E₂ group was subcutaneously injected with E₂ (10 μg·kg^-1·d^-1). Both interventions were performed once daily for 28 d. Behavioral assessments were conducted using the open field test (OFT), forced swimming test (FST), and sucrose preference test (SPT). Serum sex hormone levels were detected by ELISA. Golgi staining was used to observe the number and length of pyramidal neuron branches and assess their morphological changes in the mPFC. Western blot and whole-cell patch-clamp electrophysiology were used to detect the protein expression of vesicular glutamate transporter 1 (VGLUT1) and the frequency of miniature excitatory postsynaptic currents (mEPSC) of pyramidal neurons in the mPFC to evaluate presynaptic Glu levels; the protein expressions of the amplitude of postsynaptic density protein 95 (PSD95), N-methyl-D-aspartate receptor subtype 2B (NMDAR2B), N-methyl-D-aspartate receptor subtype 2A (NMDAR2A), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), and mEPSC amplitude to evaluate postsynaptic Glu activity; the protein expressions of presynaptic glutamic acid decarboxylase (GAD-65/67), GABA vesicular transporter (VGAT), and the frequency of miniature inhibitory postsynaptic currents (mIPSC) of pyramidal neurons in the mPFC to evaluate presynaptic GABA levels; and the protein expressions of postsynaptic GABA type A receptor subunit γ-2 (GABA_ARγ²), Gephyrin, and mIPSC amplitude to evaluate postsynaptic GABA activity, thereby assessing the Glu/GABA balance.

Compared with the control group, the exploration time and distance in the central zone of the OFT (P<0.001), the SPT index (P<0.001), the serum levels of E₂ and progesterone (PROG)(P<0.01), the number of dendritic branches, total dendritic length, Sholl radius, the number of intersections of mPFC pyramidal neurons (P<0.001, P<0.05), the protein expression levels of VGLUT1, NMDAR2B, GAD-65/67, Gephyrin, and VGAT (P<0.05, P<0.01), and the frequency of mIPSC (P<0.001) were all decreased in the model group. In contrast, the immobility time in the FST (P<0.05), the serum follicle-stimulating hormone (FSH) level (P<0.01), the protein expression levels of PSD95, NMDAR2A, and GABA_ARγ² in the mPFC (P<0.05), and the amplitude of mEPSC and frequency ratio of mEPSC/mIPSC (P<0.01) were significantly increased. Compared with the model group, the exploration time and distance in the central area of the OFT (P<0.001, P<0.05), SPT index (P<0.001), number of dendritic branches, total dendritic length, radius of concentric circles and number of intersections (P<0.001, P<0.01, P<0.05), protein expression levels of VGLUT1, GAD-65/67, Gephyrin, and VGAT (P<0.05, P<0.01), and mIPSC frequency (P<0.001, P<0.01) were significantly increased in the E₂ and EA groups. Conversely, the FST immobility time (P<0.01, P<0.05), expression levels of PSD95, GABA_ARγ² and NMDAR2A (P<0.05, P<0.001), as well as the mEPSC amplitude and mEPSC/mIPSC frequency ratio (P<0.01, P< 0.05) were decreased in both groups. In the E₂ group, the serum E₂ and PROG levels increased (P<0.01), while the serum FSH level decreased (P<0.01); in the EA group, the protein expression of NMDAR2B increased (P<0.01).

EA can improve the morphology and connectivity of pyramidal neurons in the mPFC and regulate synaptic structural and functional plasticity mediated by the Glu/GABA balance, thereby exerting a therapeutic effect on perimenopausal depression.