Suppressive Effect of Cyproheptadine on L-DOPA-induced Growth Hormone Release in Man

Nakai, Yoshikatsu; Imura, Hiroo

doi:10.1507/endocrj1954.22.357

Cited by 6 publications

(1 citation statement)

References 11 publications

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“…methysergide and mainly cyproheptadine [2,II,32]. Methysergide, in addition to the serotonin blocking activity, has been reported to possess a paradoxic stim ulating activity on the same receptor [20], and enhances sleep-related GH secretion [28].…”

Section: Discussionmentioning

confidence: 99%

Depending on the Stimulus, Central Serotoninergic Activation by Fenfluramine Blocks or Does not Alter Growth Hormone Secretion in Man

Casanueva¹,

Villanueva²,

Peñalva³

et al. 1984

Neuroendocrinology

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The role of serotonin (5-HT) in the hypothalamic regulation of human growth hormone (GH) was reassessed through the use of fenfluramine, which selectively releases 5-l·lT from presynaptic terminals. Oral administration of L-dopa plus propranolol induced a potent and sustained GH release in the subjects tested (26 ± 6 ng/ml). The administration of fenfluramine (20 mg i.v. as bolus plus 20 mg/30 min i.v.) completely suppressed the L-dopa-induced GH secretion (2 ± 0.5 ng/ml). On the other hand, when arginine (30 g/30 min i.v.) was used as a GH stimulant of medium intensity (12.7 ± 2.8 ng/ml), fenfluramine at the same dose was not able to alter the pattern of pituitary secretion (11.5 ± 4.2 ng/ml). Fenfluramine alone induced a slight nonsignificant decrease in GH values with a parallel and significant increase in prolactin (PRL) secretion in accordance with the proposed serotoninergic activity of the drug. Rat PRLsecretion by pituitaries incubated in vitro was inhibited by dopamine. Fenfluramine added to the system did not counteract the dopaminergic reduction of PRL release, making unlikely the possibility of an antagonism at the dopaminergic receptor as mechanism of action of fenfluramine on PRL secretion. In conclusion, depending on the stimulus under study, serotoninergic activation by fenfluramine either inhibits or does not alter GH secretion in man. No proof of a serotoninergic stimulatory component on GH regulation has been detected in this study. Fenfluramine is a valuable tool in neuroendocrinological studies, dealing with serotoninergic mechanisms.

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Section: Discussionmentioning

confidence: 99%