Abstract
In order to elucidate the effects of thyroid function on central nervous activity, the thresholds for electrically- and chemically-induced seizures, the pattern of maximal electroshock convulsions and the duration of postictal depression were determined in normal, thyroxin-treated, thyroidectomized and propylthiouraciltreated rats. The results obtained were as follows:
1 . Thyroxin decreased electroshock threshold for minimal seizures (increased brain excitability), whereas thyroidectomy and propylthiouracil increased this threshold (decreased brain excitability).
2. Thyroxin decreased total duration of maximal (tonic-clonic) electroshock seizures by shortening the clonic phase. Thyroidectomy increased total duration by markedly prolonging the hindleg extensor component of the tonic phase whereas propyithiouracil increased total duration by prolonging the flexor component.
3. Thyroxin slightly accelerated and thyroidectomy markedly accelerated recovery from maximal electroshock seizures. In contrast, propylthiouracil moderately prolonged postictal recovery.
4. Thyroxin increased susceptibility to Metrazol-induced seizures, whereas thyroidectomy and propyithiouracil both decreased susceptibility to such seizures.
Since certain effects of propylthiouracil unexpectedly differed from those of thyroidectomy, the possibility that propyLthiouracil has a direct depressant effect on the central nervous system must be considered. All the changes in seizure properties exhibited by the propyithiouracil-treated rats are characteristic of those caused by anticonvulsant drugs. A comparison of propyithiouracil with phenobarbital and diphenylhydantion is presented (table 4).
Quantitative information has been presented which indicates the intimate relationship between brain function and level of activity of the thyroid gland.
Footnotes
- Received July 25, 1952.
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