Effect of Pinealectomy and Melatonin on Feed Consumption and Thyroid Hormone Secretion Rate.

Ishibashi, Toshiko; Hahn, Do Won; Srivastava, Laxmi S.; Kumaresan, Perianna; Turner, C. W.

doi:10.3181/00379727-122-31215

Cited by 42 publications

(20 citation statements)

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“…Px in some [26,39,41] but not all [6] experimental conditions is associated with an increase in thyroid secre tion rate and thyroid hypertrophy in rats. In 1972 Relkin postulated that the pineal gland has an inhibitory influence on thyrotropin-releasing hormone (TRH) secretion; his postulate was based on the finding that 3 days after Px in rats there was an acute and transient increase in serum TSH and PBI.…”

Section: Discussionmentioning

confidence: 99%

Efferent Neuroendocrine Pathways of Sympathetic Superior Cervical Ganglia

Cardinali¹,

Pisarev²,

Barontini³

et al. 1982

Neuroendocrinology

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The acute effect of superior cervical ganglionectomy (SCGx) on the pituitary-thyroid axis was examined in rats subjected to surgery 3–24 h earlier. SCGx caused an abrupt decline in thyroid norepinephrine content (an index of degeneration of sympathetic nerve terminals) to 5–10% of controls between 8 and 16 h. Rats subjected to SCGx 14 h earlier exhibited a significant depression of thyroid ¹³¹I uptake, total and free serum T₄ levels and serum TSH levels. The injection of 250 mU of bovine TSH, while resulting in similar increases of radioimmunoassayable serum TSH in both SCGx and sham-operated rats, brought about a significant increase of total and free serum T₄ only in sham-operated controls; TSH treatment augmented serum T₃ levels in both groups. In order to assess the involvement of the pineal gland in the changes of activity of the pituitary-thyroid axis after SCGx, rats were pinealectomized (Px) or sham-Px and 3 days later they were subjected to SCGx or sham-SCGx; all animals were killed at the time of expected degeneration of nerve terminals (i.e. 14 h after SCGx). The depressive effects of SCGx on ¹³¹I uptake and free serum T₄ levels were observed regardless of whether the pineal was present; in contrast, Px impaired significantly or blocked the effect of SCGx on TSH and total serum T₄ levels. Pineal removal resulted in a significant increase of serum T₃ levels of SCGx rats. Blood flow estimated from the uptake of a tracer dose of ⁸⁶Rb diminished significantly in the thyroid and pineal glands of SCGx rats while remaining unchanged in the adenohypophysis or medial basal hypothalamus. These results indicate that at the time of nerve terminal degeneration in the SCG territory a functional depression of the pituitary-thyroid axis takes place, as revealed by the occurrence of low serum TSH and Tt levels and impaired thyroid ¹³¹I uptake. The effect of acute SCGx is best explained by both central and peripheral mechanisms rather than by an exclusive central depressive effect on TSH secretion because: (a) exogenous TSH injection did not increase serum T₃ levels in SCGx rats; (b) depressed thyroid ¹³¹I uptake and serum-free T₄ levels, and normal serum TSH concentration were found in SCGx previously subjected to Px.

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Section: Discussionmentioning

confidence: 99%

Efferent Neuroendocrine Pathways of Sympathetic Superior Cervical Ganglia

Cardinali¹,

Pisarev²,

Barontini³

et al. 1982

Neuroendocrinology

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“…Scepovic [96], for example, found increased iodine uptake by the thyroid glands of pinealectomized rats. Increased thyroid hormone secretion rate was also reported to occur in pinealectomized rats [42]. Other investigators, however, found no significant effect of pinealectomy on iodine up take [76], thyroid weight, or iodine release by the thyroid gland [58],…”

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confidence: 99%

Evidence for Pineal Gland Modulation of the Neuroendocrine-Thyroid Axis

Vriend¹

1983

Neuroendocrinology

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Experiments with rats and hamsters have provided evidence for an inhibitory action of the pineal gland on the neuroendocrine-thyroid axis. While maintenance of these animals in short photoperiod results in reduced levels of circulating thyroxin (T4), pinealectomy restores the levels to normal. Recent studies suggest that an active pineal gland produces a substance which inhibits thyrotrophin-releasing hormone release from the hypothalamus. Several investigators have concluded that endogenous melatonin, produced in the pineal gland, could account for the inhibitory action of the pineal gland on blood T4 levels. Although melatonin administration has been reported to inhibit blood T4 levels in both rats and hamsters, under certain experimental conditions melatonin administration can be demonstrated to have a counter-antithy-rotrophic effect resulting in increased blood levels of T4 and thyrotrophin. Assay of blood levels of melatonin of rats and hamsters under various experimental conditions will be necessary to distinguish physiological from pharmacological effects of melatonin. Lesion studies as well as studies with melatonin implants in the brain, suggest that the site of action is in the anterior hypothalamus. The effects of melatonin on the neuroendocrine-thyroid axis are similar to its effects on the neuroendocrine-gonadal axis, leading to the hypothesis of a common site of action for the thyroid and gonadal effects of melatonin. Although many pineal ‘factors’ have been postulated to account for the action of this gland, an action of melatonin on the serotonergic system of the brain stem could account for the data.

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“…In 1970, Rowe et al 6 observed that PX did not affect plasma TSH levels. In 1979, Brammer et al 7 observed that the TRH content of the hypothalamus, the TSH content of the pituitary and plasma, and the serum levels of free T 3 and T 4 were not affected by PX. Additionally, Peschke et al 17 showed that PX may induce a state of prolonged hypothyroidism.…”

Section: Discussionmentioning

confidence: 99%

“…There is some evidence that the pineal gland is involved in various endocrine functions, and its effect on the thyroid has been investigated in particular, by several authors who suggest that melatonin inhibits thyroid function by suppressing the production of pituitary TSH [1][2][3] , while others state that melatonin has a stimulatory effect 4,5 , or that its effects on the thyroid are negligible 6,7 . Thus, this is a highly controversial topic.…”

Section: Introductionmentioning

confidence: 99%

C cells in the thyroid of pinealectomized rats

Lima

Freitas

et al. 2003

Rev. Hosp. Clin.

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PURPOSE: To study quantitatively C cells in the thyroids of non-isogenic rats to determine the possible effects of pinealectomy on the number of these cells, and consequently on the synthesis and secretion of calcitonin. METHODS: Twenty male rats of an outbred strain (200-300 g) were used in the present study. One group of 10 animals was pinealectomized 50 days prior to sacrifice. Thyroid tissue was stained for calcitonin (Dako Corporation) at a 1:1500 dilution. The number of C cells observed was expressed as number of cells/cm². Data were analyzed statistically by Mann-Whitney test. RESULTS: The number of C cells in pinealectomized and normal animals ranged from 489 to 2084 per cm² and 227 to 1584 per cm², respectively, a difference that was statistically significant (P <0.05). CONCLUSIONS: These results showed consistent differences in the number of C cells after pinealectomy when compared to controls. We believe that pinealectomy increases the number of C cells in the rat thyroid.

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Effect of Pinealectomy and Melatonin on Feed Consumption and Thyroid Hormone Secretion Rate.

Cited by 42 publications

References 1 publication

Efferent Neuroendocrine Pathways of Sympathetic Superior Cervical Ganglia

Efferent Neuroendocrine Pathways of Sympathetic Superior Cervical Ganglia

Evidence for Pineal Gland Modulation of the Neuroendocrine-Thyroid Axis

C cells in the thyroid of pinealectomized rats

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