Patch-clamp recordings of thermal effects of magnetic stimulation on the physiological characteristic of rat hippocampal neurons

Transcranial magnetic stimulation (TMS) has proven to be an invaluable tool both in clinical practice and basic brain research. However, many concomitant effects of TMS are still incompletely understood, including thermal effects induced by TMS. The present study investigated how thermal effects induced by magnetic stimulation influence the properties of the spontaneous excitatory postsynaptic current (sEPSC) of hippocampal CA1 pyramidal neurons. We have demonstrated that a 50-Hz low-frequency electromagnetic field with intensities of 7, 14, and 23 mT can induce thermal heating in artificial cerebrospinal fluid(aCSF) from 25 to 40?C over a period of 15 min. We also report that the thermal effects induced by TMS directly influence the properties of sEPSC in hippocampal CA1 pyramidal neurons. Double measures were taken to control the temperature across experiments in order to ensure the accuracy of the temperature measurement of the aCSF. These novel findings provide important insight into the thermal effects induced by TMS as well as their consequences.