Kinetics of Sound Induced Convulsions In Some Inbred Mouse Strains

Abstract

Four inbred mouse stocks DBA/2, DBA/2 x A, DBA/2 x C57BL/6, and A were tested for susceptibility to audiogenic seizures. These stocks have been shown in previous expts. to have a genetic difference in seizure risk. The effect of prestimulation by sound for a period too short to produce convulsions was investigated. Prestimulation for 5- and 10-sec. periods produced enhancement of susceptibility as shown by reduced latency. This effect persisted for a period of at least 1 min. 20-second prestimulation produced a gradual decrease in susceptibility which reached its max. in 40 secs. Susceptibility returned to nearly normal levels after 80 to 100 secs. A distinctly bimodal frequency distr. of latencies was found in the various stocks. In each stock it is brought out by a particular time schedule of prestimulation. A theoretical neurophysiological model is proposed to explain these strain differences and to serve as a basis for further experimentation. The occurrence of a convulsion is ascribed to the simultaneous excitation of a critical number of neural circuits. Genetic differences in the rate of recruitment of such circuits, and in their rate of blocking, are considered to be the underlying causes of differences in seizure risk.