EFFECT OF THYROID ACTIVITY ON BRAIN FUNCTION AND BRAIN ELECTROLYTE DISTRIBUTION IN RATS1

Abstract

THE relationship between thyroid activity and brain function has long been recognized. Adequate thyroid secretion is necessary for normal differentiation of the nervous system. Athyreosis in children results in marked mental retardation, and hypothyroidism in adults is characterized by mental sluggishness. On the other hand, patients with hyperthyroidism show symptoms of increased excitability of the nervous system. Similarly, thyroidectomy, hypothyroidism and thyroxine administration produce predictable alterations in brain excitability in laboratory animals. Because of space limitations, the numerous publications concerned with the influence of the thyroid gland on the central nervous system will not be discussed here; the reader is referred to recent articles on the subject (Woodbury et al, 1952; Domino and Minz, 1953; Woodbury, 1954; Condon et al, 1954). In view of the practical importance of neurological symptoms in thyroid diseases and because of the frequent use of thyroid hormone in therapy, it was deemed of interest to study experimentally the effects of various thyroidal states on the brain function and to investigate their possible mechanism(s). In the present study, the effects of thyroidectomy, hypothyroidism, and thyroxine and triiodothyronine administration on brain function in rats were correlated with changes in body temperature, basal metabolism and brain electrolyte distribution. In addition, the influence of the adrenal gland on the effects of thyroid hormones on brain function and electrolyte metabolism was investigated.