Ontogeny of Thyroid Hormone-Processing Systems in Rat Brain
Recent morphologic, biochemical and functional evidence supports a direct role for thyroid hormones in adult brain (1–4). Nevertheless, the concept that adult brain is unresponsive to thyroid hormones continues, at least in some quarters, to prevail. By contrast, a role for the hormone during brain development has, for some time, been assumed, even though observations suggesting a cause and effect relationship between triiodothyronine (T3) in the developing brain and a T3-dependent response have been presented only recently. Evidence that T3 nuclear receptors are homologous to the products of the C-erb A protooncogene family provides a compelling rationale for involvement of these receptors in early events associated with blast cell replication and specification. This rationale is now coupled with evidence that a high degree of T3 nuclear receptor occupancy coincides in time with the period of active neurogenesis in the fetal lamb (5). However, there is as yet no demonstrated link between T3 nuclear receptor complex formation and the somewhat later effects of the hormone on growth of nerve cell processes, synaptogenesis and myelin formation, and, as yet, no evidence for participation of the T3 nuclear receptor in adult brain activities.
KeywordsDopamine Iodide Cytosol Acetyl Choline Hypothyroidism
Unable to display preview. Download preview PDF.
- 1.M. B. Dratman, F. L. Crutchfield, Y. Futaesaku, M. E. Goldberger, and M. Murray, [l25I]Triiodothyronine in the rat brain: evidence for neural localization and axonal transport derived from thaw-mount film autoradiography, Jl. Comp. Neurol. 260: 392 (1987)Google Scholar
- 2.M. B. Dratman, F. L. Crutchfield, J. T. Gordon, and A. S. Jennings, Iodothyronine homeostasis in rat brain during hypo- and hyperthyroidism, Am. J. Physiol. 245: 189E (1983)Google Scholar
- 7.M. B. Dratman, and F. L. Crutchfield, Synaptosomal [125I]triiodo thyronine after intravenous thyroxine, Am. J. Physiol. 4: E638 (1978)Google Scholar
- 14.Y. Mashio, M. Inada, K. Tanaka, H. Ishii, K. Naito, M. Nishilqawa, and H. Imura, High affinity w, 5,3’-L-triiodothyronine binding to synaptosomes in rat cerebral cortex, Endocrinology 110: 1257 (1982)Google Scholar
- 19.J. T. Gordon, F. L. Crutchfield, A. S. Jennings, and M. B. Dratman, Preparation of lipid-free tissue extracts for chromatographic determination of thyroid hormones and metabolites? Arch. Biochem. Biophys. 216: 407 (1982)Google Scholar
- 20.H. L. Schwartz, Effect of thyroid hormone on growth and development, in: Molecular basis of thyroid hormone action. J. H. Oppenheimer, and H. H. Samuels, eds., Academic Press New York (1983)Google Scholar
- 21.M. B. Dratman, and F. L. Crutchfield, Selective localization of triiodothyronine in mossy fiber synaptosomes of rat cerebellum, Abstract, Annual Meeting, The Endocrine Society, 1988Google Scholar