666 BILLEY LEVINSON 



errors, and time, respectively; the equivalent protected group scores were 

 13.8, 11.4, and 171.1. 



The savings percentages^ for the various groups decreased as radiation dose 

 increased. Indeed, for the 275 r group the savings score for trials was a minus 

 number. 



Discussion and Conclusions 



Neonatal rats were radiated at three levels of radiation at either 2, 4, or 6 

 days of age. Half of these animals received pretreatment with AET, a 

 chemoprotective agent. Measures of maze learning behavior, mortality, and 

 body weight were obtained. 



Acquisition and retention of the maze habit were inversely related to 

 radiation dose. However, the group receiving AET pretreatment performed 

 significantly better than the unprotected groups. Indeed, the original maze 

 performance of the protected group was hardly distinguishable from that of 

 nonirradiated animals. The protective effect of AET on both original learn- 

 ing and retention measures was most striking at the highest radiation level 

 (275 r). 



In addition to evaluation of the chemoprotective effects, the study served 

 to extend the data of a previous experiment on the efTects of neonatal ir- 

 radiation. The present data were consistent with the previously reported 

 relationship between dose level and performance deficit and with the finding 

 that time and error measures are more sensitive indicants of radiation effects. 

 It was again found that radiation in the first 6 days of life produces signifi- 

 cant decrements in adult learning. 



The mortality was directly proportional to radiation dose; however, rats 

 receiving AET had a higher survival rate. Weight at 45 days of age de- 

 creased as radiation dose increased, and the chemoprotective effect on 

 mortality and weight was observed only for the highest radiation dose. 



Recent studies have measured chemoprotection in terms of reduction of 

 radiation lethality (Benson et al., 1957; Crouch and Overman, 1957), sur- 

 vival time (Preston et al., 1959), depression of blood forming organs 

 (Cronkite et al, 1951), number of cataracts (von Sallman et al., 1951), 

 splenic atrophy (Patt et al, 1953), epilation (Condit et al, 1958; Forssberg, 

 1950), and graying of hair (Kulwin, 1953) . 



The present study demonstrated the importance of measuring the efTec- 

 tiveness of chemoprotection in yet another way — by means of behavioral 

 testing. 



1 The savings percent or savings score is obtained by dividing the retention score by 

 the original learning score and converting to a percentage for each subject. 



