Effects and Mechanism of High-Frequency Repetitive Transcranial Magnetic Stimulation on Motor Function in Rats with Middle Cerebral Artery Occlusion Model

<bold>Objective</bold>To investigate the effects of high-frequency repetitive transcranial magnetic stimulation (rTMS) at different frequencies on motor function and its potential mechanisms of action in a rat model of middle cerebral artery occlusion (MCAO). <bold>Methods</bold> Thirty healthy male Sprague Dawley rats were selected. The MCAO model was established using the modified Longa filament method and randomly divided into five groups (n=6 per group): Control group, Model group, Intervention group 1, Intervention group 2, and Intervention group 3. Interventions began on the second post-operative day. The Control group received acoustic stimulation only. Intervention groups 1, 2, and 3 received rTMS at 5 Hz, 15 Hz, and 30 Hz, respectively. The stimulation intensity was set at 80% of the average resting motor threshold (RMT), with a stimulation time of 3 s, inter-train interval of 6 s, and a total of 1260 pulses per session. All groups received one intervention daily for 14 consecutive days. Neurological deficit was assessed using the Modified Neurological Severity Score (mNSS), and forelimb grip strength of the affected side was measured using a Grip-Strength Meter (Ugo Basile, Italy, Model 47200) on post-operative days 3, 7, and 14. Upon completion of the intervention, cortical levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were quantified using ELISA kits. Protein expression levels of Postsynaptic Density Protein 95 (PSD-95), Synapsin-1, Neuronal Nuclei (NeuN), and β-actin were determined by Western Blot analysis.<bold>Results</bold>(1) mNSS Score: Compared to pre-intervention levels, mNSS scores were significantly increased on days 3, 7, and 14 in the Control, Intervention 1, Intervention 2, and Intervention 3 groups (P&lt;0.05). Compared to the Control group, the Model, Intervention 1, Intervention 2, and Intervention 3 groups exhibited significantly lower mNSS scores on days 3, 7, and 14 (P&lt;0.05). Compared to the Model group, the Intervention 1, Intervention 2, and Intervention 3 groups showed significantly higher mNSS scores on days 3, 7, and 14 (P&lt;0.05). (2) Forelimb Grip Strength: Compared to pre-intervention, grip strength was significantly lower on days 3, 7, and 14 in the Control, Intervention 1, Intervention 2, and Intervention 3 groups (P&lt;0.05). Compared to the Control group, the Model, Intervention 1, Intervention 2, and Intervention 3 groups demonstrated significantly higher grip strength on days 3, 7, and 14 (P&lt;0.05). Compared to the Model group, Intervention groups 1 and 2 exhibited significantly lower grip strength on days 3, 7, and 14 (P&lt;0.05), while Intervention group 3 showed significantly lower grip strength only on day 3 (P&lt;0.05).(3)Cortical Inflammation: Compared to the Control group, IL-1β and IL-6 levels were significantly lower in the Model, Intervention 1, Intervention 2, and Intervention 3 groups after 14 days of intervention (P&lt;0.05). TNF-α levels were significantly lower in the Model and Intervention 2 groups compared to the Control group (P&lt;0.05). Compared to the Model group, IL-6 and TNF-α levels were significantly higher in Intervention groups 1, 2, and 3 after 14 days (P&lt;0.05), with TNF-α also being significantly higher in Intervention groups 1 and 2 (P&lt;0.05). (4)Synaptic Plasticity Protein Expression: Compared to the Control group, PSD-95 and NeuN levels were significantly higher in the Model, Intervention 2, and Intervention 3 groups after 14 days (P&lt;0.05). Synapsin-1 levels were significantly higher in the Model and Intervention 3 groups compared to the Control group (P&lt;0.05). Compared to the Model group, PSD-95, Synapsin-1, and NeuN levels were significantly lower in Intervention groups 1 and 2 after 14 days (P&lt;0.05), and Synapsin-1 was significantly lower in Intervention group 3 (P&lt;0.05). <bold>Conclusion</bold> High-frequency rTMS can ameliorate neurological deficits and promote the recovery of forelimb motor function in MCAO model rats. The underlying mechanism may be associated with the modulation of key synaptic plasticity protein expression and the suppression of pro-inflammatory cytokine release.