Effect of static magnetic fields on the amplitude of action potential in the lateral giant neuron of crayfish.

International journal of radiation biology · 2004 · Mixed · Low evidence

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MixedLow evidencePaper 3667

Study snapshot

PublicationInternational journal of radiation biology · 2004

Study typeanimal

Reported directionMixed

Evidence ratingLow

Abstract

PURPOSE: To investigate whether exposure to static magnetic field (SMF) affects the passive properties of neurons that mediate tail-flip escape behavior in crayfish. MATERIALS AND METHODS: A permanent magnet was placed under the isolated nerve cord of crayfish to experience SMF at 4.74 to 43.45 mT intensity for various period of time (20 seconds to 3 hours). An intracellular electrode was impaled on the axon of the lateral giant neuron (LG) of the last abdominal ganglion of crayfish to record the evoked action potential (AP) and excitatory postsynaptic potential (EPSP). The amplitudes of evoked AP and EPSPs before and after SMF exposure were measured to study the effect of SMF exposure. RESULTS: The exposure to SMF increased the amplitude of AP in the LG depending upon both the intensity of field and duration of field exposure. The changes in AP by field exposure are likely to be mediated by the increasing level of intracellular Ca2+ in the LG because the chelating of intracellular Ca2+ would block the effects by SMF exposure, while the injection of Ca2+ into the LG could mimic the effects of SMF exposure. SMF exposure also increases the input resistance of the LG membrane. Therefore, the magnitude of the EPSP in LG evoked by electrical shock on the sensory nerves was found to be enhanced after SMF exposure. CONCLUSION: SMF is usually considered to be safe for the biological issues since no electrical current is induced via the Faraday effect. Our results showed that some passive membrane properties of neurons are affected by SMF exposure. The increase in magnitude of evoked AP and EPSP suggests an increase in the sensitivity of the LG neuron. These changes by SMF exposure may not necessarily to be harmful to animals; however, further study is needed to address the biological effects from SMF exposure, especially in nervous systems.

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AI evidence extraction

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Study typeanimal

Effect directionmixed

PopulationCrayfish (isolated nerve cord; lateral giant neuron)

Sample sizeNot supplied

Exposurestatic · 20 seconds to 3 hours

Evidence strengthLowConfidence: 78% · Peer reviewed: yes

Main findings

Exposure of the isolated crayfish nerve cord to a static magnetic field (4.74–43.45 mT) increased the amplitude of evoked action potentials in the lateral giant neuron in a manner dependent on field intensity and exposure duration. SMF exposure also increased membrane input resistance and enhanced EPSP magnitude; effects were blocked by intracellular Ca2+ chelation and mimicked by Ca2+ injection, suggesting Ca2+ involvement.

Outcomes measured

Amplitude of evoked action potential (AP)
Amplitude of excitatory postsynaptic potential (EPSP)
Input resistance of LG membrane
Intracellular Ca2+ involvement (chelation/injection experiments)

Limitations

Animal/invertebrate preparation (crayfish) with isolated nerve cord; generalizability to humans not addressed
Sample size not reported in abstract
Exposure characterization limited to magnetic flux density range and duration; other parameters not described
Mechanistic inference (Ca2+ mediation) based on chelation/injection experiments as described in abstract

View raw extracted JSON

{
  "study_type": "animal",
  "exposure": {
    "band": "static",
    "source": "permanent magnet",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "20 seconds to 3 hours"
  },
  "population": "Crayfish (isolated nerve cord; lateral giant neuron)",
  "sample_size": null,
  "outcomes": [
    "Amplitude of evoked action potential (AP)",
    "Amplitude of excitatory postsynaptic potential (EPSP)",
    "Input resistance of LG membrane",
    "Intracellular Ca2+ involvement (chelation/injection experiments)"
  ],
  "main_findings": "Exposure of the isolated crayfish nerve cord to a static magnetic field (4.74–43.45 mT) increased the amplitude of evoked action potentials in the lateral giant neuron in a manner dependent on field intensity and exposure duration. SMF exposure also increased membrane input resistance and enhanced EPSP magnitude; effects were blocked by intracellular Ca2+ chelation and mimicked by Ca2+ injection, suggesting Ca2+ involvement.",
  "effect_direction": "mixed",
  "limitations": [
    "Animal/invertebrate preparation (crayfish) with isolated nerve cord; generalizability to humans not addressed",
    "Sample size not reported in abstract",
    "Exposure characterization limited to magnetic flux density range and duration; other parameters not described",
    "Mechanistic inference (Ca2+ mediation) based on chelation/injection experiments as described in abstract"
  ],
  "evidence_strength": "low",
  "confidence": 0.78,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "static magnetic field",
    "SMF",
    "crayfish",
    "lateral giant neuron",
    "action potential",
    "EPSP",
    "input resistance",
    "calcium"
  ],
  "suggested_hubs": [
    {
      "slug": "animal-studies",
      "weight": 0.9,
      "reason": "Invertebrate (crayfish) neurophysiology experiment assessing SMF effects on neuronal properties."
    }
  ]
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1080/09553000400017424
PubMed: 15799615

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