Study type: Medical/biological study (experimental study)

Acute exposure to pulsed microwaves affects neither pentylenetetrazol seizures in the rat nor chlordiazepoxide protection against such seizures med./bio.

By: Pappas BA, Anisman H, Ings R, Hill DA
Published in: Radiat Res 1983; 96 (3): 486-496
Download citation in RIS format

Aim of study (acc. to author)

To determine whether brief pulsed microwave exposures altered susceptibility to pentylenetetrazol (PTZ, induces seizures by blocking the inhibitory effect of GABA as well as by a direct effect on neuronal membranes) seizures or the efficacy of chlordiazepoxide (CDZ) for counteracting PTZ seizures.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.7 GHz
Modulation type: pulsed
Exposure duration: continuous for 30 min

Exposure 1

Main characteristics
Frequency 2.7 GHz
Type
Charakteristic
Polarization
  • circular
Exposure duration continuous for 30 min
Modulation
Modulation type pulsed
Pulse width 2 µs
Repetition frequency 500 Hz
Pulse type rectangular
Exposure setup
Exposure source
Distance between exposed object and exposure source 110 cm
Chamber The antenna was a multiridged rectangular horn with a diagonal aperture of 20.5 cm radiating vertically downward into an anechoic chamber of 1.7 m x 2.6 m x 2.6 m.
Setup Rats were placed in vented circular acrylic cages of 15.3 cm diameter and 9.5 cm height with 6 mm thick acrylic lids and floors.
Sham exposure A sham exposure was conducted.
Additional info Up to four rats could be exposed at a time at four positions of equal power density spaced about 3 λ apart. However, due to handling constraints, only two rats were exposed at a time.
Parameters
Measurand Value Type Method Mass Remarks
power density 5 mW/cm² - measured - -
SAR 0.75 W/kg - measured - -
power density 10 mW/cm² - measured - -
SAR 1.5 W/kg - measured - ± 0.1 W/kg
power density 15 mW/cm² - measured - -
SAR 2.25 W/kg - measured - -
power density 20 mW/cm² - measured - -
SAR 3 W/kg - measured - -
Measurement and calculation details

The power to the antenna was controlled and measured using a hybrid coaxial waveguide network including a waveguide quadrature variable coupler and high power water load. Power densities were measured inside the cages using a broadband isotropic radiation monitor. The SARs were determined by measuring rectal temperature changes in anaesthetised rats irradiated for 3 min at 144 mW/cm² [Gandhi et al., 1979]. The measured SAR was in good agreement with the value of 2 W/kg at 10 mW/cm² calculated according to the Radiofrequency Radiation Dosimetry Handbook [Durney et al., 1980].

Reference articles

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

The experiments failed to provide consistent evidence for an effect of 2.70 GHz pulsed microwave exposure up to 20 mW/cm² on PTZ-induced seizures or on the efficacy of CDZ for counteracting such seizures. One consistent result across all experiments was that pulsed microwaves elevated core temperatures and this was proportional to the power density. Microwave exposure counteracted the hypothermic effects of CDZ without altering its anti-seizure efficacy. This underscores the dissociation between thermal and pharmacological effects of microwave exposure.

Study character:

Study funded by

Related articles