Thyroid hormone influence on the susceptibility of mice to audiogenic seizures.

Serum thyroxine levels peak earlier and are significantly higher in audiogenic seizure-susceptible DBA/2J mice than in seizure-resistant C57BL/6J mice during early postnatal life. The seizure susceptibility of DBA/2J mice is suppressed by administration of an antithyroid drug or by radiothyroidectomy, while the seizure susceptibility of C57BL/6J mice is enhanced by treatment with excess thyroxine.

Genetic linkage between the AH locus and a major gene that inhibits susceptibility to audiogenic seizures in mice.

Mice of the DBA/2 (D2) strain are highly susceptible to sound-induced seizures at 21 days of age; whereas, mice of the C57BL/6 (B6) strain are resistant to these seizures. Although the difference in susceptibility to audiogenic seizures (ASs) between these two strains is inherited as a multiple-factor trait, an association was observed between susceptibility to ASs and the Ah locus. The Ah locus controls the inducibility of aryl hydrocarbon hydroxylase (AHH) activity by a number of aromatic hydrocarbons. B6 mice carry the Ahb allele and have inducible AHH activity; whereas, D2 mice carry the Ahd allele and have noninducible activity. Inducibility is inherited as a Mendelian dominant trait in crosses between these strains. Mice carrying the Ahb allele are generally less susceptible to ASs sat 21 days of age than are mice carrying the Ahd allele. The combined results from B6 X D2 recombinant inbred strains, congenic strains (where the Ahb allele was placed into the D2 genome and the Ahd allele placed into the B6 genome), the B6D2F1 X D2 backcross generation, and a random survey of various inbred strains, suggest that the association between these two traits is due to genetic linkage, rather than to pleiotrophy or to chance. A major gene that inhibits susceptibility to ASs appears to be closely linked to the Ah locus. This gene has been designated Ias, for inhibition of ASs. A large portion of the genetic variability of AS susceptibility may be due to the segregation of Ias.

Genetic analysis of audiogenic seizure susceptibility in C57BL/6J X DBA/2J recombinant inbred strains of mice.

The inheritance of susceptibility to audiogenic seizures (ASs) was studied in the C57BL/6J (B6) and DBA/2J (D2) progenitor strains, their reciprocal F(1) hybrids, backcross generations and in 21 B6 x D2 recombinant inbred (RI) strains of mice at 21 days of age. All of the D2 mice tested experienced ASs, whereas none of the B6 mice responded to the sound. Although 23% of the F(1) mice experienced wild running, they were generally as resistant to ASs as their B6 parents. Mice of the F(1)x B6 backcross generation were also resistant to ASs. In the F(1)x D2 backcross generation, however, a significant preponderance (72%) of AS-susceptible mice was found. No significant association was observed between any of the four coat-color phenotypes that were segregating in this generation and susceptibility to ASs. A continuous distribution of mean seizure severity scores and several new audiogenic response phenotypes, distinctly different from the phenotypes of either progenitor strain, were found among the 21 RI strains. These and the results from the F(1)x D2 backcross generation suggest that the difference in AS susceptibility between 21-day-old B6 and D2 mice cannot be under the control of a single locus. In addition, no association was found between AS susceptibility and the chromosome 4 markers Lyb-2, Mup-1 and b among the 21 RI strains. An association was observed, however, between AS susceptibility and the Ah locus. Several of the RI strains that were AS resistant at 21 days of age became AS susceptible as adults. One RI strain was susceptible to ASs at both young and adult ages. The B6, D2 and F(1) mice were completely resistant to ASs at adult ages. Genetic differences were found among the RI strains for the incidence, onset, duration, and type of severity of ASs. A remarkable amount of phenotypic variability in the audiogenic response, which can be attributed only to the influence of environmental factors, occurred within several of the RI strains. A multiple-factor mode of inheritance involving a physiological threshold can account for our observations.

Psychomotor epilepsy and violence in a group of incarcerated adolescent boys.

The authors report the finding of psychomotor epilepsy in 18 of 97 incarcerated delinquent boys. Number of psychomotor symptoms was correlated with degree of violence in the members of this group. In addition, psychomotor symptoms were correlated more strongly with certain psychotic symptoms than with soft neurological signs or intellectual deficits. The relationship of violence to ictal and interictal states is explored.

Focal epilepsy with mesial temporal sclerosis after acute meningitis.

Following acute meningitis associated with severe convulsions in childhood, two patients had chronic, drug-resistant, temporal lobe epilepsy. This disorder was preceded by an entirely natural development, in one case extending for nine years and in the other case for eight years. Each patient was treated with right anterior temporal lobectomy. Classic mesial temporal sclerosis (Ammon's horn sclerosis) was found in both patients. Relief of the epilepsy was associated with remission of the concomitant social and psychiatric handicaps. At least ten years of follow-up are required in the evaluation of the treatment of early brain infections. Chronic focal epilepsy after childhood meningitis with febrile convulsions merits neurosurgical consideration.

Inherited convulsive disorders in mice.

In this chapter, we review the major inherited convulsive disorders found in mice and discuss their possible relationship to specific clinical seizure disorders in humans. These disorders in mice include audiogenic seizures, the epilepsy (El) mouse, various spontaneous seizures, the tottering/leaner syndrome, seizures associated with cerebellar abnormalities, seizures associated with myelin disorders, and alcohol withdrawal seizures. We find that for most major types of epilepsy in humans, there exists a similar counterpart in the mouse. Because human and rodent nervous systems respond similarly to seizure-provoking stimuli, it is possible that biochemical and physiological mechanisms of naturally occurring convulsive disorders are also similar in these species. The use of recombinant inbred (RI) and congenic mouse strains for genetic and biochemical studies of audiogenic seizures is presented. Using these strains, we have identified a major gene, Ias, that inhibits the spread of seizure activity. This gene was found through its close linkage with the Ah locus on chromosome 17. We also found that juvenile-onset and adult-onset audiogenic seizures are controlled by different genetic systems. The problem of juvenile-onset audiogenic seizure susceptibility is especially interesting because these seizures are genetically associated with an ecto-Ca2+-ATPase deficiency among the RI strains. This deficiency is the first neurochemical trait found to be inherited together with an idiopathic convulsive disorder, and may represent a potentially important basic mechanism of epilepsy. Because the brains of human epileptics are generally inaccessible for neurochemical research, the epileptic mouse mutants offer a convenient means of pursuing this type of research. The well-known genetic constitution of the mouse, together with the availability of numerous physiologically distinct convulsive disorders, makes the mouse ideally suited for molecular, genetic, and biochemical studies of convulsive behavior.