Effects of the microphthalmic white gene on audiogenic seizure susceptibility in mice.

Audiogenic seizure susceptibility was studied in mice segregating for the microphthalmic white gene (Miwh). Previous work by Deol had indicated that mice with either one or two Miwh alleles had severe inner ear defects. A congenic inbred strain provided mice that were identical in genetic background except for single-gene substitutions at the microphthalmia locus. The three genotypes tested were Miwh/Miwh, Miwh/+, and +/+. Mice were exposed to the sound stimulus once for a 1-min period between the ages of 17 and 30 days. Heterozygous Miwh/+ mice had more seizures and were more reactant than either type of homozygote at all ages tested. Responses were low at 17 days of age, peaked sharply by 23 days, and declined markedly by 30 days.