Modulation of Low-Frequency Pulsed Magnetic Field on Hippocampal Neural Oscillation in Depression Rats

Transcranial magnetic stimulation (TMS), as a non-invasive brain stimulation technique, has been approved for some medication-resistant depression by the United States Food and Drug Administration. However, the majority of these studies have focused on the effects of high-frequency TMS, and little is known about low-frequency TMS in depression treatment. Furthermore, the potential electroneurophysiology mechanisms of TMS on the improvement of and function of the brain remain poorly understood. In the present study, a depression rat model was established by chronic unpredictable stress (CUS). Rats were exposed to low-frequency pulsed magnetic field (LFPMF) (1Hz, 20mT) for 14 days, one hour per day, then elevated plus-maze test was assessed and local field potentials (LFPs) in hippocampus were recorded. In order to analyze LFPs, sample entropy was calculated to make complexity analysis, while phase locked value and phase-amplitude coupling modulation index were used to figure out the correlation of oscillations. Our data showed that LFPMF significantly relieved CUS-induced depression-behaviors and improved the undesirable changes of the identical-frequency synchronization and theta-gamma phase-amplitude coupling in CUS rats. These findings indicated that the antidepressive-like effects of LFPMF might be associated with the LFPMF-induced improvement in neural oscillation.