Effects of bremsstrahlung and electron radiation on rat motor performance

Relatively high, rapidly delivered doses of ionizing radiation have been reported to produce an immediate decrement in performance (PD) in a number of animal species. This study investigated the effects of bremsstrahlung and electron radiation on the performance of rats unilaterally exposed in a linear accelerator at a midline tissue dose-rate of 2000 rad/min. Relative radiation effects were determined by establishing median effective doses (ED50) for rats trained on the accelerod, a shock-avoidance test of motor performance. The ED50's were based on 10-min post-exposure performance. Subjects were also tested 15-, 30-, 60- and 24 hours after exposure. Fifty-seven trained rats were exposed to bremsstrahlung radiation, and 40 trained rats were exposed to electrons. The ED50 for the bremsstrahlung field was 7977 rad and 6110 rad for the electron field, for a significantly different relative effectiveness of the electron field in producing PD of 1.31. In a direct 7700-rad comparison of effect between the two fields, the electron exposed subjects demonstrated PD for a longer period of time after exposure. The data imply that different radiation fields are not equally effective in producing performance decrement