Immediate post-exposure effects of high-peak-power microwave pulses on operant behavior of Wistar rats med./bio.

To study behavioral effects of high-peak-power microwave pulses on rats by operant schedules and to test the hypothesis that these microwaves would result in work disruption at all rates of performance. Specifically, it was designed to study conjointly both SA (specific absorption, total doses, kJ/kg) and SAR-dependent effects of such exposure.

Rats that had been trained to press a lever to receive food pellets were assigned randomly in groups to three different schedules of reinforcement (to establish three different response patterns with differential response rates): fixed-ratio schedule, variable interval schedule, and differential-reinforcement-of-low-rates (DRL schedule). The fixed-ratio schedule requires that a set number of responses be made for each reinforcement and typically produces a high rate of responding. The variable interval schedule requires only one response for the delivery of reinforcement after a certain amount of time has elapsed. The DRL schedule requires only one response after delivery of a food pellet, but only if this response is delayed for a predetermined time period.

• animal
• rat/Wistar
• whole body

Exposures at the highest dose caused an average colonic temperature rise of 2.5°C and these rats failed to respond at all for about 13 minutes after the irradiation. Their colonic temperatures had decreased to 1.1°C, or less, above their pre-exposure (normal) temperature level when the animals began to respond. The fixed-ratio schedule and variable interval schedule rats failed to reach their baseline levels of performance thereafter, while those on the DRL schedule (differential-reinforcement-of-low-rates) schedule displayed variable effects. No behavioral effects were observed at the lower dose levels. The authors concluded that the behavioral perturbations produced by pulsed microwave irradiation were thermal in nature.