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Effects of hypothalamic dopamine on growth hormone‐releasing hormone‐induced growth hormone secretion and thyrotropin‐releasing hormone‐induced prolactin secretion in goats
Author(s) -
Jin Jin,
Hashizume Tsutomu
Publication year - 2015
Publication title -
animal science journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.606
H-Index - 38
eISSN - 1740-0929
pISSN - 1344-3941
DOI - 10.1111/asj.12333
Subject(s) - medicine , endocrinology , prolactin , thyrotropin releasing hormone , hormone , dopamine , secretion , hypothalamus , growth hormone–releasing hormone , growth hormone , chemistry , biology
Abstract The aim of the present study was to clarify the effects of hypothalamic dopamine ( DA ) on the secretion of growth hormone ( GH ) in goats. The GH ‐releasing response to an intravenous (i.v.) injection of GH ‐releasing hormone ( GHRH , 0.25 μg/kg body weight (BW)) was examined after treatments to augment central DA using carbidopa (carbi, 1 mg/kg BW) and L ‐dopa (1 mg/kg BW) in male and female goats under a 16‐h photoperiod (16 h light, 8 h dark) condition. GHRH significantly and rapidly stimulated the release of GH after its i.v. administration to goats ( P < 0.05). The carbi and L ‐dopa treatments completely suppressed GH ‐releasing responses to GHRH in both male and female goats ( P < 0.05). The prolactin ( PRL )‐releasing response to an i.v. injection of thyrotropin‐releasing hormone ( TRH , 1 μg/kg BW) was additionally examined in male goats in this study to confirm modifications to central DA concentrations. The treatments with carbi and L ‐dopa significantly reduced TRH ‐induced PRL release in goats ( P < 0.05). These results demonstrated that hypothalamic DA was involved in the regulatory mechanisms of GH , as well as PRL secretion in goats.