Extremely low frequency electromagnetic fields and synaptic transmission and plasticity in rat perirhinal cortex slices

Concern is rising about possible effects of electromagnetic fields (EMF) on biological systems, in particular on nervous system. Recent evidences suggest that exposure to extremely low frequency (ELF) EMF can interfere with learning and memory processes. Since long-term potentiation (LTP) is considered to reproduce neuronal mechanisms underlying memory formation, one might suppose that ELF-EMF can affect LTP. Aim of the present work is to verify if acute exposure to ELF-EMF affects synaptic transmission and LTP maintenance in the rat perirhinal cortex. Experiments were carried out in horizontal brain slices prepared from male rats aged 20-30 days. Slices were placed in a submersion recording chamber perfused with warm (34C) oxygenated artificial cerebro-spinal fluid. Extracellular field potentials (FP) evoked by horizontal pathways stimulation were recorded in layer II/III of perirhinal cortex, and the synaptic peak amplitude was measured. During FP recording, slices were exposed to ELF-EMF (50 Hz, 2.3 mT) generated by a pair of Helmholtz coils placed around the recording chamber. In synaptic transmission experiments (n=6), slices were exposed to EMF for 60 min after 30 min of stable baseline response. In LTP experiments (n=5), EMF was applied for 30 min, starting 40 min after LTP induction by a theta-burst stimulation. Control experiments (n=6 and 5, respectively) were performed either in sham or no exposure conditions. The results obtained to date indicate that the applied ELF-EMF does not affect synaptic transmission and LTP maintenance. Experiments using different exposure conditions are currently in progress.