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To study whether exposure to static magnetic field affects the passive properties of neurons that mediate tail-flip escape behavior in crayfish.
A fast Ca2+ chelator BAPTA was pre-loaded into the lateral giant neuron. In some experiments, ruthenium red (a specific blocker for the ryanodine receptor which is the Ca2+ release channel of the endoplasmic reticulum and mitochondria) or CaCl2 were loaded into the lateral giant neuron.
|ばく露時間||2 min, 5 min, 10 min, 1 h and/or 3 h|
|ばく露装置の詳細||isolated nerve cord of cray fish in a Petri dish (3 cm in diameter) was placed above the permanent magnet|
|Additional information||A piece of isometric orthographic paper (1.5 x 1.2 cm) with 30 intercepts was glued to the surface of the magnet to assure a standard magnetic field exposure through all the preparations|
The exposure to static magnetic field increased the amplitude of action potential in the lateral giant neuron depending upon both the intensity of field and duration of exposure. The alterations in action potential are likely to be mediated by the increasing level of intracellular Ca2+ in the lateral giant neuron because the chelating of intracellular Ca2+ would block the effects by static magnetic field exposure, while the injection of Ca2+ into the lateral gaint neuron could mimic the effects of magnetic field exposure.
Static magnetic field exposure also increased the input resistance of the lateral giant neuron membrane. Therefore, the magnitude of the excitatory postsynaptic potential evoked by electrical shock on the sensory nerves was found to be enhanced after exposure.
Static magnetic field is usually considered to be safe for the biological issues. The results showed that some passive membrane properties of neurons are affected by static magnetic field exposure. The increase in magnitude of evoked action potential and excitatory postsynaptic potential suggests an increase in the sensitivity of the lateral giant neuron. These changes by static magnetic field exposure may not necessarily to be harmful to animals; however, further studies are needed to address the biological effects from static magnetic field exposure, especially in nervous systems.