STUDIES ON THE MECHANISM OF HYPOTHALAMTC CONTROL OF THYROTROPIN SECRETION:COMPARISON OF THE SENSITIVITY OF THE HYPOTHALAMUS AND OF THE PITUITARY TO LOCAL CHANGES OF THYROID HORMONE CONCENTRATION<sup>1</sup>

Yamada, Takashi

doi:10.1210/endo-65-6-920

Cited by 22 publications

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“…Yamada and Gree [50] suggested that the site of action for T4 may be both on the hypothalamus and on the pituitary gland, and Yamada [49] demonstrated that T4 injections into the paraventricular region could sup press thyroidal radioiodine metabolism. This was further supported by Kajihara and Kendall [32] using T4-agar pel lets implanted in the paraventricular region.…”

Section: Discussionmentioning

confidence: 99%

Thyroidectomy and Central Catecholamine Neurons of the Male Rat

Andersson

Eneroth²

1987

Neuroendocrinology

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Using the Falck-Hillarp methodology in combination with quantitative microñuorimetry, catecholamine (CA) levels and utilization in discrete hypothalamic CA nerve terminal systems in the male rat have been analyzed 24 h, 1, 2 and 4 weeks following thyroidectomy as well as after T₃ or T₄ restitution therapy 4 weeks after thyroidectomy. By means of high pressure liquid chromatography (HPLC), dopamine (DA) and noradrenaline (NA) levels and utilization 4 weeks after thyroidectomy have been analyzed in various brain regions. Triiodothyronine treatment (10 µg/kg, s.c, twice daily during 10 days) of 4-week athyroidic rats increased serum T₃ levels, but not T₄ serum levels. Thyroxine treatment (36 µg/kg, s.c, twice daily during 10 days) of 4-week athyroidic rats increased serum T₄ levels and the T₃ levels were found to be even slightly higher than those found in normal animals. Triiodothyronine or T₄ restitution therapy reversed the changes induced by thyroidectomy on the anterior pituitary hormones (TSH, prolactin and growth hormone) and corticosterone secretion. It is suggested that removal of thyroid hormones may be responsible for the changes in the anterior pituitary hormones and corticosterone secretions. In the quantitative microfluorimetrical analysis 24 h, 1,2 and 4 weeks after thyroidectomy, decreases in DA levels and utilization and increases in NA levels and utilization were found in the lateral palisade zone (LPZ) of the median eminence and in the parvocellular and magnocellular parts of the paraventricular hypothalamic nucleus (PA), respectively. In addition, 1-, 2- and 4-week decreases were found in DA levels and turnover in the medial palisade zone (MPZ) as well as in NA turnover in the dorsomedial hypothalamic nucleus (DM) and in the ‘border zone’ (BZ) between the medial and lateral hypothalamus ventral to the fornix. In the HPLC analysis it could be demonstrated that 4 weeks after thyroidectomy decreases in DA levels and utilization in the mediobasal hypothalamus and increases in DA levels as well as NA levels and utilization in the hypothalamus had developed. The T₃ or T₄ restitution therapies after 4 weeks of thyroidectomy counteracted the effects on CA levels and utilization in all hypothalamic CA nerve terminal systems except for the reduced NA utilization found in the DM following 4 weeks after thyroidectomy. The demonstrated reductions in DA levels and utilization in the MPZ and LPZ of the median eminence and the increases in NA levels and utilization in the PA are suggested to reflect the existence of an inhibitory dopaminergic mechanism in the median eminence and a facilitatory noradrenergic mechanism in the PA involved in the regulation of TSH secretion. These mechanisms seem to be directly or indirectly regulated by thyroid hormones. The reduced NA utilization in the DM and in the BZ after thyroidectomy is suggested to be related to the lowering of growth hormone secretion and reduction of its pul...

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Section: Discussionmentioning

confidence: 99%

Thyroidectomy and Central Catecholamine Neurons of the Male Rat

Andersson

Eneroth²

1987

Neuroendocrinology

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“…Others have reported that the response to TRF was blocked by larger amounts of thyroxine in vitro (5) and in vivo (11). Thyroxine has been effective in decreasing thyroid release of 131 I in rats when implanted directly into the hypothalamus or the anterior pituitary (21). The release of 131 I was immediately decreased after implantation in the pituitary, but was delayed by 20 hours after anterior hypothalamic placement.…”

Section: Discussionmentioning

confidence: 99%

Effect of Thyrotropin Releasing Factor (TRF) of Ovine, Bovine, Porcine and Human Origin on Thyrotropin Releasein Vitroandin Vivo

Bowers

Redding

1965

Endocrinology

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Peptide-like materials which release thyrotropin (TSH) from the pituitary in vivo and in vitro were obtained from the hypothalamus of the ox, sheep and pig and from human neurohypophysial tissue. Thyrotropic hormone releasing factor (TRF) activity was measured in vitro by the isolated rat pituitary incubation method of Saffran and Schally. TSH secreted into the medium was assayed by the release of 13I I from the thyroid gland of the mouse as described by McKenzie and by the uptake of 131 I by the tadpole's thyroid as described by Bowers. Addition of TRF preparations to the incubation media significantly increased the release of TSH from the pituitaries. TSH release in vitro was related to the dose of TRF preparations from all 4 species. One TRF preparation was active in vitro at a dose of 10 ng. TRF activity was also measured in vivo in the rat. TRF preparations from each species increased plasma TSH levels in thyroidectomized, triiodothyronine-treated rats. These studies support the concept that the hypothalamus takes part in the regulation of TSH release from the anterior pituitary gland. (Endocrinology 77: 609, 1965)

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Why I Am Still Waiting for a Free Trip to Stockholm

Greer

1978

Pioneers in Neuroendocrinology II

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STUDIES ON THE MECHANISM OF HYPOTHALAMTC CONTROL OF THYROTROPIN SECRETION:COMPARISON OF THE SENSITIVITY OF THE HYPOTHALAMUS AND OF THE PITUITARY TO LOCAL CHANGES OF THYROID HORMONE CONCENTRATION¹

Cited by 22 publications

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Thyroidectomy and Central Catecholamine Neurons of the Male Rat

Thyroidectomy and Central Catecholamine Neurons of the Male Rat

Effect of Thyrotropin Releasing Factor (TRF) of Ovine, Bovine, Porcine and Human Origin on Thyrotropin Releasein Vitroandin Vivo

Why I Am Still Waiting for a Free Trip to Stockholm

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STUDIES ON THE MECHANISM OF HYPOTHALAMTC CONTROL OF THYROTROPIN SECRETION:COMPARISON OF THE SENSITIVITY OF THE HYPOTHALAMUS AND OF THE PITUITARY TO LOCAL CHANGES OF THYROID HORMONE CONCENTRATION1

Cited by 22 publications

References 0 publications

Thyroidectomy and Central Catecholamine Neurons of the Male Rat

Thyroidectomy and Central Catecholamine Neurons of the Male Rat

Effect of Thyrotropin Releasing Factor (TRF) of Ovine, Bovine, Porcine and Human Origin on Thyrotropin Releasein Vitroandin Vivo

Why I Am Still Waiting for a Free Trip to Stockholm

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STUDIES ON THE MECHANISM OF HYPOTHALAMTC CONTROL OF THYROTROPIN SECRETION:COMPARISON OF THE SENSITIVITY OF THE HYPOTHALAMUS AND OF THE PITUITARY TO LOCAL CHANGES OF THYROID HORMONE CONCENTRATION¹