530 DOROTHEA STARBUCK MILLER 



radiation applied early are especially eflfective in influencing the audiogenic 

 seizure response. 



We have no reasonable explanation for the basis of the heightened seizure 

 susceptibility following low level radiation. Several lines of evidence suggest 

 that seizure susceptibility may be related to a defect in carbohydrate metabo- 

 lism in brain tissue. Insulin and glutamic acid, which are among the most 

 eflfective protective agents, may compensate in part for this defect. Ginsburg 

 (1954) has screened many metabolically active substrates and antimetabo- 

 lites for their influence on audiogenic seizures in DBA mice. Some of these 

 compounds reduce and some enhance the number and severity of seizures. 

 Ginsburg postulates that deficiencies in particular enzymatic reactions lead- 

 ing to normal, controlled energy release in the nervous system are the basis 

 for the seizures. If this metabolic hypothesis is correct, the action of radiation 

 in increasing the incidence of seizures may be at the enzymatic level. At 

 present, this suggestion is speculative. 



Conclusion 



The audiogenic seizure response appears to be remarkably radiosensitive 

 in DBA mice and in hybrid generations derived from crossing DBA with 

 C57 mice. A striking increase in susceptibility to audiogenic seizures has been 

 observed following exposure to very low doses of ionizing radiation. Height- 

 ened susceptibility is indicated by an increase in frequency and severity of 

 seizures, by a higher percentage of total and fatal seizures on the first trial, 

 and by shorter latency of fatal seizures. 



In these mice, which are tested for sound sensitivity at 30 days of age, 

 chronic exposure to gamma radiation from birth throughout the 30 days, 

 at a total dosage of 0.14 r, caused a significant increase in seizure suscepti- 

 bility. In mice exposed to Co*^" between days 23 and 30, a dosage of 350 

 mrad per day (total, 1.5-2 rad) resulted in heightened susceptibility. 



In DBA/2 mice, the effect of glutamic acid in protecting them from 

 seizures was negated when the animals were maintained in an environment 

 of 4.8 mrad per day (5-10 times background). 



Evidence was presented indicating that the level of radioactive fallout 

 from April, 1957, through 1959, was sufficient to enhance the frequency and 

 severity of seizures. 



In addition to the primary physiologic eflfect on the seizure response, evi- 

 dence of genetic change aflfecting seizure susceptibility in both DBA/1 and 

 C57BL6 was noted following chronic exposure to gamma radiation at 5-10 

 times backa;round. 



