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 by a linear accelerator (LINAC facility) 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, which is a shock-avoidance test of motor performance. The ED50s were based on 10-min postexposure performance. Subjects were also tested at 15, 30, 60, and 120 min and 24 hr after exposure. Fifty-seven trained rats were exposed to bremsstrahlung radiation, and 40 trained rats were exposed to electrons. The ED50 was 8121 rad for the bremsstrahlung field and 6110 rad for the electron field, for a significantly different relative effectiveness of the electron field in producing PD of 1.35. The data imply that different radiation fields are not equally effective in producing PD.