title: Effect of melatonin injected into the third ventricle on growth hormone secretion in Holstein steers.
abstract: The effects of melatonin (MEL) injection into the third ventricle (3V) on growth hormone (GH) secretion were investigated in conscious Holstein steers. A stainless steel cannula was stereotaxically implanted in the 3V based on the ventriculogram. In Exp. 1, three doses of MEL (100, 300 or 600 microg) were injected into the 3V through the cannula and the GH concentration after the injection was determined. In Exp. 2, intracerebroventricular (icv) and intravenous (iv) injections of MEL (100 microg) and GH-releasing hormone (GHRH; 0.25 microg/kg body weight), respectively, were performed simultaneously to examine the effect of MEL on GHRH-induced GH release. The icv injection of MEL significantly stimulated GH release at 100 microg. The increase in GH concentrations by 100 microg of MEL was persistent. Intravenous injection of GHRH dramatically increased GH release. The injection of MEL did not alter GHRH-induced GH release. These results suggest that MEL stimulates GH secretion possibly through the hypothalamus in cattle.
authors.affiliation: Department of Physiology and Genetic Regulation, National Institute of Agrobiological Sciences, Ibaraki, Japan.
authors.forename: Etsuko
authors.initials: E
authors.lastname: Kasuya
authors.forename: Shiro
authors.initials: S
authors.lastname: Kushibiki
authors.forename: Madoka
authors.initials: M
authors.lastname: Sutoh
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Saito
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ito
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Yayou
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Sakumoto
authors.forename: Koichi
authors.initials: K
authors.lastname: Hodate
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood / Q000502:physiology*; D004347:Drug Interactions; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D008550:Melatonin / Q000008:administration & dosage*
chemical_list: D007987:Gonadotropin-Releasing Hormone; D013006:Growth Hormone; D008550:Melatonin