RADIATION AND AUDIOGENIC SEIZURES IN MICE 515 



TABLE I 



Comparison' of Audiogenic Seizure Incidence in Variois Groups of Mice 

 Before and During Low Level Radiation in Animal Quarters " 



"^ Data based on four daily trials. 



'' September. 1949, through June. 1952. in Whitman Laboratory. 



<■ July. 1952, through August, 1956, in Re i R. 



<■ BxC = backcross to C57. 

 <■ B\D = backcross to DB.\. 



columns headed ■"Whit" are data collected from September. 1949. through 

 June, 1952, in Whitman Laboratory. The columns headed "Room R'' are 

 data collected from July. 1952. through August, 1956. in the frame building. 

 In each generation within the 4 basic crosses, the mice had become signifi- 

 cantly more seizure prone while in Room R. In no group was this trend 

 re\ersed. In addition to the greatly elcxated seizure frequency, the propor- 

 tion of fatal seizures was also higher. 



Painstaking examination failed to reveal any change in food, water, dis- 

 infectants, background sound level, personnel, or procedure which might be 

 responsible for the increase in seizure susceptibility. After the second coat- 

 color mutation i Miller and Potas, 1955) appeared in the colony, we had 

 the mouse quarters monitored for possible radiation. A le\'el of 5-10 times 

 backgroimd (0.1 to 0.2 mrad per hour) was detected, supplied from a Co''" 

 source in a neighboring laboratorv. unshielded on the side facing our 

 windows. By chance, the rack directly in front of these windows was used to 

 house the de\eloping litters, which were therefore exposed to the maximal 

 dose in the room. Within the 30 day period before being tested for seizure 

 susceptibility, each mouse received at total of approximately 0.15 r. 



