Many authors have reported that destruction of an area of hypothalamus resulted in inhibition of thyroid activity (Harris, Greer, Barrnett, Rheichlin, etc.), electrical stimulation of hypothalamus caused hyperfunction of thyroid (Ellics, Harris, Savino, D´Angelo, etc.) and direct injection of minute amount of thyroxin into the hypothalamus appeared to inhibit thyroid activity (Yamada and Green).
The author tried further to clarify the relationship between hypothalamus and thyroid activity by direct injection of chemical solutions into the rabbit hypothalamus and measuring the animal serum protein-bound iodine levels.
Korean white male rabbits weighing 1.8 kg were used and placed in a quiet room under constant room temperature. Solutions used for the injection were distilled water. 0.001% pure L-thyroxin solution in 0.01N NaOH solvent, physiological saline and 396 hypertonic saline solution. 0.05 cc of them were injected into the hypothalamus bilaterally using 30 gauge injection needle and the animal blood were collected in 6 hours intervals for at least 24 hours. The injection sites were determined according to the stereotaxic coordinates for Korean rabbit. Determinations of serum PBI levels of the collected blood were performed according to the method described by Cardiner & Burn, a modified Barker´s micromethod.
The results obtained were as follow:
1. The normal serum PLi levels of Korean rabbits were stable within 0.6 ,ugm% range when periodically determined for as long as 3 days.
2. The serum PBI levels measured after preoptic area, anterior and middle hypothalamus were punctured with 30 gauge injection needle showed no significant change or slight decrease, whereas those after puncture of posterior hypothalamus showed marked decrease.
3. The serum PBI levels measured after physiological saline was injected into the preoptic area, anterior and middle hypothalamus showed no change or slight decrease, whereas those after injected into the posterior hypothalamus showed marked decrease.
4 The serum PBI levels measured after thyroxine solution was injected into the preoptic area, anterior and posterior hypothalamus showed marked decrease, whereas those after injected into the middle hypothalamus showed slight or moderate decrease.
5. The serum PBI levels measured after distilled water was injected into the preoptic area showed significant rise, whereas those after injected into the anterior, middle and posterior hypothalamus showed a significant decrease.
6. The serum PBI levels measured after 3% hypertonic saline solution was injected into the preoptic area, anterior, middle and posterior hypothalamus showed a marked decrease.
7. The serum PBI levels were measured after injection of physiologic saline solution, 0.001% thyroxine solution, distilled water and 3% hypertonic saline solution into the cerebral cortex, hippocampus,
amygdaloid area and thalamus. The cerebral cortex produced no significant change to any solution_ injected. The amygdaloid area produced significant change to all solutions injected. The hippocampus. produced significant change only to hypertonic saline solution.
It can be thereby concluded that the areas of hypothalamus e.g. preoptic area, anterior, midle and posterior hypothalamus act in a direct or indirect way as higher regulatory centers for serum PBL metabolism.
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