Epileptic seizures in rats homozygous for two mutations, zitter and tremor.

In the rat, zitter (zi) and tremor (tm) are autosomal recessive mutations that in homozygotes caused curled whisker hair, and tremor when the animals move. In both mutant types, the presence of many vacuoles gives the central nervous system a spongy appearance. The mutants differ sharply in one important characteristic: zitter rats are fertile, tremor rats are sterile. The F1 hybrids between zitter homozygous females and a tremor heterozygous male were all normal, and data from subsequent crosses revealed that zi and tm are neither allelic nor linked to each other. In animals homozygous for both mutations, an epileptic seizure frequently and spontaneously occurred from 7 or 8 weeks of age. Although the epileptic seizure has not been studied in detail, it may be an excellent animal model of epilepsy.