Short-term low intensity PMF does not improve functional or histological outcomes in a rat model of transient focal cerebral ischemia

Stimulation with pulsed magnetic fields (PMF) is a non-invasive technique that can modulate neural activity and has the potential to facilitate functional recovery and tissue preservation/repair following brain injury. The effect of low intensity (8 mT) PMF on functional recovery and infarct tissue volume was assessed in a middle cerebral artery occlusion model of transient focal ischemia in Spontaneously Hypertensive rats. Rats received a combination of PMF protocols, including high and low frequencies and recovery was monitored over eight days. PMF treatment had no effect on functional recovery or infarct volume. Infarcted tissue accounted for ≈8% of total brain volume, encompassing both cortical and subcortical structures. The microglial and astrocytic response to PMF treatment was monitored and there was no change in glial scarring, however there was increased macrophage infiltration in animals that received chronic high (6-9 Hz) and low (1 Hz) stimulation. There was no effect of PMF on the degree of cell death observed within the ischemic core, with no TUNEL positive cells observed in the non-infarcted tissue. No detrimental side-effects of PMF were observed, indicating that low-intensity PMF may have limited safety concerns for future human and animal studies.

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