Serotonin stimulates GH secretion through a direct pituitary action: studies in hypophysectomized autografted animals and in perifused pituitaries

Abstract

To analyze a possible direct action of serotonin (5-hydroxytryptamine) at pituitary level in GH secretion, two experimental models were used: hypophysectomized autografted rats and perifused pituitaries. Adult male rats were hypophysectomized and their own pituitaries placed under the right kidney capsule. Ten days later an intra-atrial cannula was inserted. The next day, blood samples were obtained before and every 10 min during a 2 h period after the injection of saline or 5-hydroxytryptamin (1 or 2 mg/kg iv). Plasma volume was replaced with saline. Both doses of 5\ x=r eq-\ hydroxytryptamine elicit a strong release of GH, the effect being dose-dependent. In pituitaries perifused with 5-hydroxytryptamine (100 \g=m\mduring 115 min or 1, 10 and 100 \g=m\mduring 15 min), a significant release of GH was also observed. These results suggested that 5-hydroxytryptamine may stimulate GH secretion through a direct pituitary action.

Specific stimulation of brain serotonin mediated neurotransmission by dexfenfluramine does not restore growth hormone responsiveness in obese women

“…Thus, studies using more specific serotoninergic medication do not reveal a significant influence of central 5-HT mediated neurotransmission upon GH release in obese humans. Evidence in rats suggest that 5-HT exerts its influence upon GH release directly at the pituitary level (Lopez et al, 1986). d-FF mainly affects central serotonin systems, although it has some peripheral effects (Campbell, 1991).…”

The Effect of Cyproheptadine on Plasma Growth Hormone (GH) and on Somatostatin Response to GH-Releasing Hormone in Man

“…More recently, serotonin receptors have been identified and characterized in the rat pituitary gland (Souza 1986). Further support for direct serotoninergic action at the pituitary level comes from in vivo studies showing direct GH release in autografted rat pituitaries perifused with 5-hydroxytryptamine (Lopez, Gonzalez and Aguilar 1986). However, 5hydroxytryptamine did not stimulate GH release from the pituitary in vitro (Kato et al 1980).…”

Serotonin/growth hormone/insulin-like growth factors axis on pre- and post-natal development: A contemporary review

“…Data on the exact role of 5HT on the release of GH are actually controversial 15 this is probably due to the complexity of the serotonergic system and the many receptor sub types involved. Furthermore, there are many evidences that 5HT acts not only through the action of the hypothalamus, but also directly on the pituitary gland 16 . Therefore, it seems that 5HT affects the basal secretion of pituitary GH through some of its receptors, as well as through the hypothalamic mechanism of GHRH/ SS.…”