Summary
A study was made of the effects of thiouracil and excess thyroxine on the hypothalamus of the male rat. Measurements were taken of the area of the cross-sections of nuclei in the ganglion cells of sixteen hypothalamic nuclei and areas. At the same time study was made of variations in the distribution and amount of aldehyde-fuchsin-positive neurosecretory material in the different parts of the neurosecretory system. The investigation covered the development and restoration phases of change brought about by both thiouracil and excess thyroxine.
Thiouracil generally caused a reduction in the volume of the ganglion cell nuclei in all nuclei of the hypothalamus investigated, while treatment with thyroxine led to a growth in nuclear volume. The changes were at least at one stage of treatment, in almost all nuclei or areas investigated, of the highly significant level. Restoration towards normal nuclear volume after discontinuation of treatment was rapid; generally it was perceptible within 4 days. The neurosecretory material diminished under the influence of both thiouracil and excess thyroxine after 18 days of treatment, remaining so until the end of the test period (30 days). The tendency to return to normal after completion of 18 days of treatment was observed within 8 days, and normal level was reached in 14 days.
The functional significance of the changes is discussed: no localizable and restricted area of the hypothalamus was found whose nuclear reaction diverged from that of the surrounding ganglions of the brain tissue. The hypothalamus appears to react to the test conditions employed as an entity, and the activity of the neurosecretory ganglions follows this general reaction.
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This work was supported by grants from the Sigrid Jusélius Foundation, Helsinki, Finland and the National Research Council for Medical Sciences, Finland.
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Talanti, S. The effect of thiouracil and excess thyroxine on the hypothalamus of the rat with special reference to neurosecretory phenomena. Z. Zellforsch. 79, 92–109 (1967). https://doi.org/10.1007/BF00335246
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DOI: https://doi.org/10.1007/BF00335246