Prolonged microwave irradiation of rats: effects on concurrent operant behavior med./bio.

To study operant behavior in small animals during exposure to pulse modulated microwave irradiation. Two measures of performance were used: 1) cued, fixed-ratio (FR) bar pressing for food reinforcement and 2) noncued bar pressing in the absence of food reinforcement.

• animal
• rat/Long-Evans
• whole body

At 1.5 mW/g, the levels of cued operant responding by control and exposed rats were comparable, and showed similar progressive diminutions over the course of each daily session. Noncued operant responding was more variable, but again comparable, with both groups of animals showing similar, progressive declines in rate of responding during each session.
At 3.6 mW/g, no specific effects on cued operant response rates were observed. However, there was an initial and transient increase in the rate of extinction of noncued responding.
At 6.7 mW/g, cued response rates were slightly reduced, whereas there was a major decrease in noncued operant responding followed by a sharp rebound during the first post-microwave irradiation week. This marked reduction in noncued operant responding at microwave irradiation onset was in contrast to the relative stability and persistence of FR (fixed-ratio) responding for food reinforcement.