Endocrinology, Vol 124, 1224-1229, Copyright © 1989 by Endocrine Society

ARTICLES

Possible mechanisms involved in growth hormone secretion induced by galanin in the rat

Y Murakami, Y Kato, A Shimatsu, H Koshiyama, N Hattori, N Yanaihara and H Imura
Department of Medicine, Kyoto University Faculty of Medicine, Japan.

The mechanisms by which central or systemic administration of galanin stimulates GH secretion were investigated in either conscious or urethane-anesthetized male rats. Intracerebroventricular injection of synthetic porcine galanin, a 29-amino acid gut-brain peptide (0.12, 0.6, and 3 nmol/rat), resulted in a dose-related increase in plasma GH. The plasma GH level was increased by an N-terminal galanin fragment [galanin-(1-19)], but not by C-terminal fragments [galanin-(2-29) and - (21-29)]. Intravenous injection or infusion of galanin (0.6 and 3 nmol/100 g BW) also raised plasma GH. The plasma GH increase induced by galanin was inhibited by pretreatment with rabbit antiserum specific for rat GRF. Pretreatment with yohimbine or phenoxybenzamine, alpha- adrenergic blockers, or picrotoxin, a gamma-aminobutyric acid (GABA) antagonist, blunted the plasma GH increase induced by intracerebroventricular injection of galanin. On the other hand, the plasma GH increase induced by iv injection of galanin was suppressed by picrotoxin, but not by phenoxybenzamine. These findings suggest that 1) both central and systemic administration of galanin stimulate GH secretion in the rat; 2) the N-terminal structure of galanin is required to stimulate GH secretion; 3) the stimulating effect of galanin is mediated, at least in part, by hypothalamic GRF; and 4) central alpha-adrenergic and GABAergic mechanisms may be involved in GH release induced by central administration of galanin, whereas systemic injection of galanin stimulates GH release predominantly through GABAergic mechanisms in the rat.

This article has been cited by other articles:

				J. Iqbal, T. R. Manley, P. Ciofi, and I. J. Clarke Reduction in Adiposity Affects the Extent of Afferent Projections to Growth Hormone-Releasing Hormone and Somatostatin Neurons and the Degree of Colocalization of Neuropeptides in Growth Hormone-Releasing Hormone and Somatostatin Cells of the Ovine Hypothalamus Endocrinology, November 1, 2005; 146(11): 4776 - 4785. [Abstract] [Full Text] [PDF]

				M. J. Naylor, E. Ginsburg, T. P. Iismaa, B. K. Vonderhaar, D. Wynick, and C. J. Ormandy The Neuropeptide Galanin Augments Lobuloalveolar Development J. Biol. Chem., August 1, 2003; 278(31): 29145 - 29152. [Abstract] [Full Text] [PDF]

				J. F. Todd, C. M. B. Edwards, M. A. Ghatei, and S. R. Bloom The differential effects of galanin-(1---30) and -(3---30) on anterior pituitary hormone secretion in vivo in humans Am J Physiol Endocrinol Metab, June 1, 2000; 278(6): E1060 - E1066. [Abstract] [Full Text] [PDF]

				A. Giustina and J. D. Veldhuis Pathophysiology of the Neuroregulation of Growth Hormone Secretion in Experimental Animals and the Human Endocr. Rev., December 1, 1998; 19(6): 717 - 797. [Abstract] [Full Text]

				D. Ray and S. Melmed Pituitary Cytokine and Growth Factor Expression and Action Endocr. Rev., April 1, 1997; 18(2): 206 - 228. [Abstract] [Full Text]