Effects of acute low-level microwaves on pentobarbital-induced hypothermia depend on exposure orientation.

Abstract

Two series of experiments were performed to study the effects of acute exposure (45 min) to 2,450-MHz circularly polarized, pulsed microwaves [1 mW/cm2, 2-mus pulses, 500 pps, specific absorption rate (SAR) 0.6 W/kg] on the actions of pentobarbital in the rat. In the first experiment, rats were irradiated with microwaves and then immediately injected with pentobarbital. Microwave exposure did not significantly affect the extent of the pentobarbital-induced fall in colonic temperature. However, the rate of recovery from the hypothermia was significantly slower in the microwave-irradiated rats and they also took a significantly longer time to regain their righting reflex. In a second experiment, rats were first anesthetized with pentobarbital and then exposed to microwaves with their heads either pointing toward the source of microwaves (anterior exposure) or pointing away (posterior exposure). Microwave radiation significantly retarded the pentobarbital-induced fall in colonic temperature regardless of the orientation of exposure. However, the recovery from hypothermia was significantly faster in posterior-exposed animals compared to those of the anterior-exposed and sham-irradiated animals. Furthermore, the posterior-exposed rats took a significantly shorter time to regain their righting reflex than both the anterior-exposed and sham-irradiated animals.

AI evidence extraction

Main findings

In rats exposed for 45 min to 2,450-MHz pulsed microwaves (1 mW/cm2; SAR 0.6 W/kg), microwave exposure did not significantly change the extent of pentobarbital-induced colonic temperature fall when exposure preceded pentobarbital injection, but recovery from hypothermia was slower and time to regain righting reflex was longer. When rats were anesthetized first and then exposed, microwaves significantly retarded the pentobarbital-induced temperature fall regardless of orientation; recovery from hypothermia and righting reflex recovery were faster in posterior-exposed animals compared with anterior-exposed and sham-irradiated animals.

Outcomes measured

• Pentobarbital-induced hypothermia (colonic temperature fall and recovery rate)
• Time to regain righting reflex

Limitations

• Sample size not reported in abstract
• Only acute exposure (45 min) studied
• Animal model; generalizability to humans not addressed in abstract
• Exposure orientation effects suggest results may depend on experimental setup

{
    "study_type": "animal",
    "exposure": {
        "band": "microwave",
        "source": null,
        "frequency_mhz": 2450,
        "sar_wkg": 0.59999999999999997779553950749686919152736663818359375,
        "duration": "45 min"
    },
    "population": "Rats",
    "sample_size": null,
    "outcomes": [
        "Pentobarbital-induced hypothermia (colonic temperature fall and recovery rate)",
        "Time to regain righting reflex"
    ],
    "main_findings": "In rats exposed for 45 min to 2,450-MHz pulsed microwaves (1 mW/cm2; SAR 0.6 W/kg), microwave exposure did not significantly change the extent of pentobarbital-induced colonic temperature fall when exposure preceded pentobarbital injection, but recovery from hypothermia was slower and time to regain righting reflex was longer. When rats were anesthetized first and then exposed, microwaves significantly retarded the pentobarbital-induced temperature fall regardless of orientation; recovery from hypothermia and righting reflex recovery were faster in posterior-exposed animals compared with anterior-exposed and sham-irradiated animals.",
    "effect_direction": "mixed",
    "limitations": [
        "Sample size not reported in abstract",
        "Only acute exposure (45 min) studied",
        "Animal model; generalizability to humans not addressed in abstract",
        "Exposure orientation effects suggest results may depend on experimental setup"
    ],
    "evidence_strength": "low",
    "confidence": 0.7399999999999999911182158029987476766109466552734375,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "microwaves",
        "2450 MHz",
        "pulsed",
        "circularly polarized",
        "SAR",
        "pentobarbital",
        "hypothermia",
        "colonic temperature",
        "righting reflex",
        "exposure orientation"
    ],
    "suggested_hubs": []
}

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