Zoological Studies

Vol. 36 No. 2, 1997

Review Article

Neuroendocrine Regulation of Growth Hormone Secretion and Growth in Fish

Chun Peng1 and Richard E. Peter2,*

1Department of Biology, York University, North York, Ontario M3J 1P3, Canada
2Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada

Chun Peng and Richard E. Peter (1997) Neuroendocrine regulation of growth hormone secretion and growth in fish. Zoological Studies 36(2): 79-89. Growth in fish is regulated in large part by the brain neuroendocrine - growth hormone (GH) - insulin-like growth factor axis. GH secretion is in turn regulated by multiple factors from the .brain, with both stimulatory and inhibitory neurohormones acting on the somatotrophs seasonally.
Somatostatin is the primary inhibitor of basal and stimulated GH secretion . Norepinephrine and serotonin also have inhibitory actions on GH release. On the other hand, GH secretion is stimulated by a number of neuroendocrine factors, including growth hormone-releasing factor (GRF), dopamine (DA), gonadotropin-releasing hormone (GnRH), neuropeptide Y (NPY), thyrotropin-releasing hormone (TRH), cholecystokinin (CCK), bombesin (BBS), and activin . While GRF and DA are more potent in stimulating GH secretion in sexually regressed fish, GnRH, NPY, and TRH have greater stimulatory effects on GH secretion in sexually mature (l.a., prespawning) fish. Sex steroids, in particular estradiol, influence the responsiveness of the somatotrophs to neuroendocrine factors. The integrated action of sex steroids and neuroendocrine factors provides a basis for the seasonal regulation of growth hormone secretion.
The brain peptide systems regulating food intake are linked to the brain neuroendocrine regulation of GH secretion. Following a meal, goldfish characteristically show a short-term increase in serum GH concentrations, and then a decrease in serum GH concentrations to below premeal levels. BBS and CCK are involved in satiation and the changes in GH secretion following a meal in goldfish . Both the neuroendocrine regulation of GH secretion and the brain regulation of feeding are multifactor ial. Understanding the integration of these systems presents a major challenge .

Key words: Fish, Growth hormone, Food intake, Neuropeptide , Monoamine.

*Correspondence: Tel: (403) 492-4757, Fax: (403) 492-7033, E-mail: REPeter@sci.ualberta.ca