Modulating effects of on-line low frequency electromagnetic fields on hippocampal long-term potentiation in young male Sprague-Dawley rat

The low frequency electromagnetic fields (LF-EMFs) are attracting more attention and studied deeply because of their effects on human health and biology. Recent reports indicate that exposure of rats to LF-EMFs induces persistent changes in neuronal activity. The studies used the following standard methods: the rats or rat brain slices were first stimulated in an external electromagnetic exposure system, and then moved to a patch clamp perfusion chamber to record electrophysiological characteristics (off-line magnetic exposure). However, this approach is susceptible to many disturbances, such as the effects of brain slice movements. In this paper, we describe a novel patch-clamp setup which is modified to allow accurate on-line LF-EMFs stimulation. We performed the computational simulations of the stimulation coils to describe the uniformity of the distribution of the on-line magnetic field. The 0.5, 1, 2 mT magnetic field of 15 Hz, 50 Hz, and 100 Hz was produced and applied to slices to study the effect of LF-EMFs on synaptic plasticity. We demonstrated that the slope of field excitatory postsynaptic potentials (fEPSPs) decreased significantly under the priming on-line uninterrupted or pulsed sinusoidal LF-EMFs stimulation. In the present study, we investigated whether LF-EMFs can induce long-term potentiation (LTP) in male Sprague-Dawley rat hippocampal slices in vitro. Interestingly, these results highlight the role of 100 Hz pulsed sinusoidal LF-EMFs only as a modulator, rather than an LTP inducer.