title: Interaction between nicotinic cholinergic receptors and alpha-2 adrenergic systems in regulating growth hormone secretion in conscious rats.
abstract: The possible role and mechanism of central nicotinic cholinergic receptors in regulating growth hormone (GH) secretion were investigated in conscious, unrestrained male rats. The administration of galanin (GAL), a neuropeptide, GH-releasing hormone (GHRH) and UK 14304, an alpha-2 adrenergic agonist, caused increases in plasma GH levels. Pretreatment of the animals with hexamethonium significantly reduced GAL- and GHRH-induced GH secretion, but UK 14304-induced GH release was not affected. Neosurugatoxin, a nicotinic cholinergic neurotoxin, partially inhibited GAL-induced GH release. Pretreatment with neostigmine elevated basal plasma GH levels and partially inhibited GAL-induced GH secretion. However, GHRH- and UK 14304-induced GH release was additive to the effect of neostigmine. Yohimbine inhibited GH release induced by UK 14304, GAL and GHRH. Neostigmine-induced GH secretion was partially inhibited by yohimbine and phenoxybenzamine. These findings suggest that central nicotinic receptors have a stimulatory role in regulating GH secretion and that the nicotinic cholinergic system coupled with the alpha-2 adrenergic mechanism is involved in GH secretion induced by galanin in conscious rats.
authors.affiliation: Department of Internal Medicine, Kyoto University Faculty of Medicine, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Shimatsu
authors.forename: T
authors.initials: T
authors.lastname: Tanoh
authors.forename: I
authors.initials: I
authors.lastname: Tsuji
authors.forename: N
authors.initials: N
authors.lastname: Yanaihara
authors.forename: H
authors.initials: H
authors.lastname: Imura
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D000068438:Brimonidine Tartrate; D003243:Consciousness; D019004:Galanin; D013006:Growth Hormone / Q000097:blood / Q000378:metabolism*; D008297:Male; D008978:Mollusk Venoms / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D010902:Pituitary Gland / Q000378:metabolism; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D011978:Receptors, Nicotinic / Q000502:physiology*
chemical_list: D000316:Adrenergic alpha-Agonists; D008978:Mollusk Venoms; D010455:Peptides; D011810:Quinoxalines; D018341:Receptors, Adrenergic, alpha-2; D011978:Receptors, Nicotinic; D000068438:Brimonidine Tartrate; C036793:neosurugatoxin; D019004:Galanin; D013006:Growth Hormone