Evidence for Effects on Neurology and Behavior - BioInitiative Report

hippocampus was blocked by pretreatment of the animals with the opiate-antagonists naloxone
and naltrexone, suggesting involvement of endogenous opioids in the effect. Endogenous opioids
are a group of peptides synthesized by the nervous system and have pharmacological properties
like opiates. They are involved in a variety of physiological functions such as stress reactions,
temperature-regulation, motivational behaviors, etc. Our further research showed that the effects
of RFR on central cholinergic activity could be classically conditioned to cues in the exposure
environment [Lai et al., 1987c]. These effects of RFR on cholinergic functions are similar to
those reported in animals after exposure to stressors [Finkelstein et al., 1985; Lai, 1987; Lai et al.,
1986c].
When different power densities of RFR were used, a dose-response relationship could be
established from each brain region [Lai et al., 1989a]. Data were analyzed by probit analysis,
which enables a statistical comparison of the dose-response functions of the different brain
regions. It was found that a higher dose-rate was required to elicit a change in HACU in the
striatum, whereas the responses of the frontal cortex and hippocampus were similar. Thus, under
the same irradiation conditions, different brain regions could have different sensitivities to RFR.
In further experiments to investigate the contributory effect of different parameters of RFR
exposure, we found that the radiation caused a duration-dependent biphasic effect on cholinergic
activity in the brain. After 20 instead of 45 min of RFR exposure as in earlier experiments, an
increase in HACU was observed in the frontal cortex, hippocampus, and hypothalamus of the rat
[Lai et al., 1989b], and these effects could be blocked by pretreatment with the opiate antagonist
naltrexone, suggesting the effects are also mediated by endogenous opioids.
Experiments [Lai et al., 1988] were then carried out to compare the effects of exposure in
two different systems that produced different energy absorption patterns in the body of the
exposed animal. Rats were exposed to pulsed (2 s pulses, 500 pps) or continuous-wave 2450-
MHz RFR in the circular waveguide and the miniature anechoic chamber exposure systems
designed by Guy [Guy, 1979; Guy et al., 1979] with the whole body average SAR kept at a
constant level of 0.6 W/kg. In the circular waveguide rats were exposed to circularly polarized
RFR from the side of the body. In the miniature anechoic chamber rats were exposed dorsally
with plane-polarized RFR. The circular waveguide produced a more localized energy absorption
pattern than the miniature anechoic chamber. Detailed dosimetry studies in the body and brain of
rats exposed in these two exposure systems had been carried out [Chou et al., 1984, 1985a].
After 45 min of exposure to the RFR, a decrease in HACU was observed in the frontal cortex in
all exposure conditions studied (circular waveguide vs miniature anechoic chamber, pulsed vs
continuous-wave). However, regardless of the exposure system used, HACU in the hippocampus
decreased only after exposure to pulsed, but not continuous-wave RFR. Striatal HACU was
decreased after exposure to either pulsed or continuous-wave RFR in the miniature anechoic
chamber, but no significant effect was observed when the animal was exposed in the circular
waveguide. No significant effect on HACU was found in the hypothalamus under all the
exposure conditions studied. Thus, each brain region responded differently to RFR exposure
depending on the parameters. <strong>Effects</strong> on the frontal cortex were independent of the exposure
system or use of pulsed or continuous- wave RFR. The hippocampus only responded to pulsed
but not to continuous-wave RFR. Response of the striatum depended on the exposure system
used. The neurochemical changes were correlated with the dosimetry data of Chou et al. [1985a]
on the local SARs in different brain areas of rats exposed to RFR in these two exposure systems.
The dosimetry data showed that the septum, where the cell bodies of the hippocampal
cholinergic pathway are located, had the lowest local SAR among eight brain areas measured in
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