Changes in Serum TSH Level After Intraventricular Injection of Various Neuromediators in Rats

Abstract

The influence of various neuromediators on pituitary TSH secretion in rats has been investigated. Noradrenaline 50 \g=m\g/rat,dopamine 50 \g=m\g/rat, serotonine-creatinine-sulphate 100 \g=m\g/rat,gamma-aminobutyric acid 100 \g=m\g/rat,pilocarpine 1 mg/rat, histamine 100 \g=m\/rat were administered into the lateral ventricle of the brain. All agents were dissolved in Parker's fluid. Two control groups of animals were given Parker's fluid and subjected to surgical manipulations, respectively. Plasma TSH level was estimated after 30 min by means of radioimmunoassay. The increase in the TSH level was observed after the injection of serotonine and noradrenaline (4.0 and 3.1 ng/ml, respectively) as compared with control group (0.7 ng/ml).The influence of various neuromediators on pituitary thyrotrophin (TSH) secre¬ tion has been investigated mainly in dopaminergic and noradrenergic system (Refetoff et al. 1972;Spaulding et al. 1972;Rapaport et al. 1973;Tuomisto et al. 1975) as well as the serotoninergic system (Grimm 8c Reichlin 1973;Mess 8c Peter 1974.The effect of various neuromediators on pituitary thyrotrophic function can be investigated in two ways. The indirect method consists in the intravenous injection of some drugs that influence either the neurohormone level or the functional condition of the appropriate receptor: they inhibit the synthesis or retard the disintegration of neuromediator, block or stimulate the receptor.

Effects of Substance P, Angiotensin II, Oxotremorine and Prostaglandin D₂ on Thyrotropin Secretion in Rats

“…There are many reports concerning the effects of amines, peptides and prostaglan dins (PGs) on thyrotoropin (TSH) secretion [1,2,4,7,9,10,12,13,19,21,23,[26][27][28][29][30][31][32][33], Substance P (SP), PG D2 and angiotensin II are found in the hypothalamus in rats [3,8,10,13,15], suggesting that they may affect thyrotropin-releasing hormone (TRH) and TSH secretion. A few studies have been made on the role of the cholinergic system in TSH secretion [1,10,12,21], Therefore, the authors investigated the effects of SP, angio tensin II, PG D2 and oxotremorine, a cholin ergic agonist, on TRH and TSH release in rats and have studied the possible mecha nism by which these substance exert their effect on TRH and TSH release.…”

“…A few studies have been made on the role of the cholinergic system in TSH secretion [1,10,12,21], Therefore, the authors investigated the effects of SP, angio tensin II, PG D2 and oxotremorine, a cholin ergic agonist, on TRH and TSH release in rats and have studied the possible mecha nism by which these substance exert their effect on TRH and TSH release.…”

Central Serotoninergic Stimulation by Fenfluramine Challenge Does Not Affect Plasma Thyrotropin-Stimulating Hormone Levels in Man

“…Data from animal studies support both stimulatory and inhibitory roles for this neurotransmitter. Stimulation of TSH release by 5-HT has been suggested in studies em ploying intraventricular injection of 5-HT [17,18,39] and intraventricular and parenteral administration of the 5-HT precursor 5-hydroxytryptophan (5-HTP) [5,32] and the 5-HT synthesis inhibiting p-chlorophenylalanine [5,33], Con versely, inhibition of TSH release by 5-HT has been sugges ted in studies employing inirahypothalamic implants or in traventricular injection of 5-HT [15,23] and intraventricular or parenteral administration of the 5-HT agonist quipazine [19], the 5-HT-releasing ¿/-fenfluramine [8,9], the 5-HT pre cursor tryptophan [22,24,25], and p-chlorophenylalanine [31]. Further, studies employing 5-HTP suggest that 5-HT inhibits cold-induced activation of TSH [27,37].…”

Serotonin and thyroid gland in the lizardPodarcis sicula

“…In fact, literature data (Holak et al, 1978;Jordan et al, 1978) have demonstrated that 5-HT causes hypersecretion of hypophyseal TSH, which, in turn, causes an increase in thyroid-hormone release. Our results confirm these data, since, throughout the treatment, 5-HT significantly increased TSH plasma levels.…”