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Naltrexone pretreatment blocks microwave-induced changes in central cholinergic receptors.

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Lai H, Carino MA, Wen YF, Horita A, Guy AW · 1991

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Microwave radiation at 0.6 W/kg SAR altered brain receptors through the opioid system, suggesting current safety limits miss non-thermal biological effects.

Plain English Summary

Summary written for general audiences

Researchers exposed rats to microwave radiation at 2450 MHz (the same frequency as WiFi and microwave ovens) and found it altered brain receptors involved in memory and learning. When they gave the rats naltrexone (a drug that blocks opioid receptors) before exposure, it prevented these brain changes. This suggests microwave radiation affects the brain through the body's natural opioid system.

Why This Matters

This study reveals a concerning mechanism by which microwave radiation affects brain chemistry. The researchers found that exposure at just 0.6 W/kg SAR - well below current safety limits - altered cholinergic receptors in brain regions critical for memory and cognition. What makes this particularly significant is that blocking the opioid system prevented these changes, suggesting EMF exposure triggers a stress response involving the body's natural pain-relief mechanisms. The fact that different exposure durations produced opposite effects (increases vs decreases in receptors) indicates the brain's adaptive response to this artificial stimulus. This research adds to a growing body of evidence that current safety standards, which only consider heating effects, miss important biological impacts occurring at much lower power levels.

Exposure Details

SAR
0.6 W/kg
Power Density
1 µW/m²
Source/Device
2450 MHz
Exposure Duration
Ten 20-min sessions.

Exposure Context

This study used 1 µW/m² for radio frequency:

This study used 0.6 W/kg for SAR (device absorption):

Building Biology guidelines are practitioner-based limits from real-world assessments. BioInitiative Report recommendations are based on peer-reviewed science. Check Your Exposure to compare your own measurements.

Where This Falls on the Concern Scale

Study Exposure Level in ContextStudy Exposure Level in ContextThis study: 1 µW/m²Extreme Concern - 1,000 uW/m2FCC Limit - 10M uW/m2Effects observed in the Slight Concern rangeFCC limit is 10,000,000x higher than this level
A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 2.45 GHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 2.45 GHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Study Details

The aim of this study is to investigate Naltrexone pretreatment blocks microwave-induced changes in central cholinergic receptors.

Repeated exposure of rats to pulsed, circularly polarized microwaves (2,450-MHz, 2-microseconds puls...

These findings, which confirm earlier work in the authors' laboratory, were extended to include pretreatment of rats with the narcotic antagonist naltrexone (1 mg/kg, IP) before each session of exposure. The drug treatment blocked the microwave-induced changes in cholinergic receptors in the brain. These data further support the authors' hypothesis that endogenous opioids play a role in the effects of microwaves on central cholinergic systems.

Cite This Study
Lai H, Carino MA, Wen YF, Horita A, Guy AW (1991). Naltrexone pretreatment blocks microwave-induced changes in central cholinergic receptors. Bioelectromagnetics 12(1):27-33, 1991.
Show BibTeX
@article{h_1991_naltrexone_pretreatment_blocks_microwaveinduced_1134,
  author = {Lai H and Carino MA and Wen YF and Horita A and Guy AW},
  title = {Naltrexone pretreatment blocks microwave-induced changes in central cholinergic receptors.},
  year = {1991},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/2012619/},
}
PubMed: 2012619

Cited By (39 papers)

Quick Questions About This Study

Yes, naltrexone completely blocked microwave-induced brain changes in this 1991 study. Rats given naltrexone before 2450 MHz exposure showed no alterations in brain receptors, while untreated rats experienced significant changes in memory-related brain areas like the hippocampus and frontal cortex.
Research suggests yes. A 1991 study found that naltrexone (an opioid blocker) prevented all microwave-induced brain changes, indicating that 2450 MHz radiation affects the brain through the body's natural opioid pathways rather than through direct cellular damage alone.
2450 MHz radiation (microwave oven frequency) causes biphasic changes in brain cholinergic receptors involved in memory and learning. Short exposures increased receptors in the hippocampus, while longer exposures decreased them in both hippocampus and frontal cortex areas.
Pulsed 2450 MHz radiation at very low power (1 mW/cm²) altered brain receptor concentrations in memory-critical areas. Ten 45-minute sessions increased hippocampal receptors, while ten 20-minute sessions decreased receptors in both hippocampus and frontal cortex regions.
Evidence suggests yes. Since naltrexone (which blocks opioid receptors) prevented all 2450 MHz-induced brain changes in this study, researchers concluded that WiFi-frequency radiation affects the central nervous system by activating the body's natural opioid system rather than direct mechanisms.