Changes in synaptic efficacy in rat brain slices following extremely low‐frequency magnetic field exposure at embryonic and early postnatal age

Abstract

An earlier study demonstrated changes in synaptic efficacy and seizure susceptibility in adult rat brain slices following extremely low-frequency magnetic field (ELF-MF) exposure. The developing embryonic and early postnatal brain may be even more sensitive to MF exposure. The aim of the present study was to determine the effects of a long-term ELF-MF (0.5 and 3 mT, 50 Hz) exposure on synaptic functions in the developing brain. Rats were treated with chronic exposure to MF during two critical periods of brain development, i.e. in utero during the second gestation week or as newborns for 7 days starting 3 days after birth, respectively. Excitability and plasticity of neocortical and hippocampal areas were tested on brain slices by analyzing extracellular evoked field potentials. We demonstrated that the basic excitability of hippocampal slices (measured as amplitude of population spikes) was increased by both types of treatment (fetal 0.5 mT, newborn 3 mT). Neocortical slices seemed to be responsive mostly to the newborn treatment, the amplitude of excitatory postsynaptic potentials was increased. Fetal ELF-MF exposure significantly inhibited the paired-pulse depression (PPD) and there was a significant decrease in the efficacy of LTP (long-term potentiation induction) in neocortex, but not in hippocampus. On the other hand, neonatal treatment had no significant effect on plasticity phenomena. Results demonstrated that ELF-MF has significant effects on basic neuronal functions and synaptic plasticity in brain slice preparations originating from rats exposed either in fetal or in newborn period.

Potential Impact of Space Environments on Developmental and Maturational Programs Which Evolved to Meet the Boundary Conditions of Earth: Will Maturing Humans Be Able to Establish a Functional Biologic System Set Point under Non-Earth Conditions?

“…Certainly, many tissues including the brain are sensitive to exogenous magnetic and electromagnetic fields [discussed in [5,6]]. It also appears that fetal or neonatal brains may be particularly sensitive to very low frequency magnetic fields, dependent in part, on which part of the brain is assessed [5], with the hippocampus being one in the rodent brain that exhibits sensitivity [5,7]. However, the effects of prenatal exposure to such fields in somewhat inconsistent in mammals, and variability has been reported [reviewed in [8]].…”

An Extremely Low Frequency Magnetic Field and Global Cerebral Ischemia Affect Pituitary ACTH and TSH Cells in Gerbils

“…This represents a source of environmental pollution that may induce a variety of effects in organisms. Among them are changes in excitability and synaptic plasticity [Balassa et al, ], cell morphology [Rauš Balind et al, ], the expression, affinity and density of receptors [Janać et al, ; Li et al, ], and oxidative stress [Jelenković et al, ; Selaković et al, ] in the brain, as well as animal behavior [Szemerszky et al, ; Janać et al, ; Madjid Ansari et al, ]. Cerebral ischemia is a pathophysiological condition induced by restricted blood flow through the brain and is a leading cause of death worldwide.…”

Pulsed magnetic stimulation modifies amplitude of action potentials in vitro via ionic channels‐dependent mechanism

“…Exposure to magnetic fields modulates several processes in a variety of biological preparations. Effects exerted in the nervous system by exposure to static [Prina‐Mello et al, ; Oliviero et al, ] and oscillating [Azanza and Del Moral, ; Balassa et al, ] magnetic fields have been clearly demonstrated. However, results were often inconsistent and in spite of recent efforts [Modolo et al, ], comprehensive mechanisms of magnetic field action have not yet been proposed.…”

“…Previous investigations revealed that magnetic fields modulated neuronal activity recorded from brain slices [Wieraszko, ; Wieraszko et al, ; Ahmed and Wieraszko, ; Tokay et al, ; Varro et al, ; Balassa et al, ], and fragments of sciatic nerve [Ahmed and Wieraszko, ]. PMF‐induced amplification of nerve cell activity in hippocampal slices, expressed as an increase in the amplitude of evoked potentials [Wieraszko, ], was correlated to rise in concentration of 3'‐5'‐cyclic adenosine monophosphate (cAMP) [Hogan and Wieraszko, ], and with enhancement of release and uptake of the neurotransmitter, glutamate [Wieraszko ; Wieraszko et al, ; Wieraszko and Ahmed, ].…”