Microwave radiation and dextroamphetamine: Evidence of combined effects on behavior of rats

Combined effects of microwave radiation and dextroamphetamine were investigated in studies of six male albino rats that performed on a temporal reinforcement (DRL) schedule. During one‐hour sessions, only a response that was delayed by 18 s or more after a preceding response was reinforced by a food pellet. Thirteen weeks of pretraining on the schedule generated a low‐and‐steady rate of responding, with the largest proportion of responses occurring after the appropriate interval of time. Initially, a dose‐effect function was obtained in the absence of radiation for a range of doses of dextroamphetamine (0.25 to 5.0 mg kg −1 ). Smaller doses of the drug produced an increase in response rate with consequent reduction in frequency of reinforcement. Maximal rates of responding occurred at 1.0 to 2.0 mg kg −1 . Yet higher doses of the drug produced a decline of rate, then complete cessation of responding. A dose‐effect function was then obtained for the same doses of the drug during three‐month regimens involving single or multiple exposures to radiation. In the single‐exposure condition, after the drug was administered to a subject, it was exposed for one‐half hour to 2.45‐GHz pulsed microwaves at an averaged power density of 1 mW cm −2 (2 μS pulses; 500 pulses s −1 ). The resulting whole‐body dose rate was near 200 μ W g −1 . In the multiple‐exposure condition, a subject was exposed daily to microwaves under the same field conditions, except on days when dextroamphetamine was administered and behavior was observed. Under both conditions of radiation, the dose‐effect function was displaced such that the maximal behavioral effect was obtained at doses lower than those without radiation.