Genetic analysis of serum thyroxine content and audiogenic seizures in recombinant inbred and congenic strains of mice

Abstract

Abstract We previously proposed that the audiogenic seizure (AGS) susceptibility of 21 ± 1-day-old DBA/2 (D2) mice may result from an early postnatal elevation in serum thyroxine (T 4) concentration. In the present study we used seven C57 × DBA (BXD) recombinant inbred strains and the D2.B6- Ias b congenic strain to study the association between serum T 4 content and susceptibility to AGS. The D2.B6- Ias b congenic mice are genetically similar to the D2 mice except for the Ias b gene, which inhibits AGS susceptibility. The total and estimated free serum T 4 concentrations in these strains at 14 ± 1 days of age were compared with the previously determined AGS susceptibilities of these strains at 21 ± 1 days of age. We found no significant correlations between serum T 4 concentration and AGS susceptibility in these strains. It is unlikely, therefore, that inherited differences in neonatal serum T 4 content are directly responsible for differences in susceptibility to AGS in 21 ± 1-day-old mice. The mechanisms by which the experimental manipulation of serum T 4 content influences AGS susceptibility are discussed.