Low-level microwave irradiation and central cholinergic systems med./bio.

To investigate the neurological effect of low-level microwave irradiation, and the biochemical and behavioral consequences of repeated exposure of rats.

In the first series of experiments the effects of acute exposure on choline uptake in four regions of the brain (striatum, frontal cortex, hippocampus, and hypothalamus) containing high amounts of cholinergic innervations were examined. In the second series of experiments it was studied whether the effects of acute (20-min) microwave exposure on central cholinergic activity could be blocked by pretreatment with narcotic antagonist naltrexone hydrochloride), since the authors have speculated that microwave irradiation is a stressor and some of their effects are mediated by endogenous opioids. Finally, the effects of microwave exposure on learning in the radial-arm maze were examined.

• animal
• rat/Sprague-Dawley

Increases in choline uptake activity in the frontal cortex, hippocampus, and hypothalamus were observed after 20 min of acute microwave exposure. Tolerance to the effect of microwaves developed in the hypothalamus, but not in the frontal cortex and hippocampus, of rats subjected to ten daily 20-min exposure sessions. Furthermore, the effects of acute microwave irradiation on central choline uptake could be blocked by pretreating the rats before radiation with the narcotic antagonist naltrexone.
Decreases in concentration of muscarinic receptors occured in the frontal cortex and hippocampus of animals subjected to ten 20-min microwave exposure sessions, whereas increase in receptor concentration occured in the hippocampus of animals exposed to ten 45-min sessions.
Radiation for 20 min before maze training had no significant effect on learning, but a significant treatment X training-session interaction was observed suggesting that the learning curves of the microwave- and sham-exposed animals are different. Retardation in learning was observed after 45 min of microwave exposure. The data showed significant treatment main effect and treatment X training-session interaction effects.