Sexual maturity modifies the responsiveness of the pituitary-interrenal axis to stress in male rainbow trout

Pottinger, T.G.; Balm, P. H.M.; Pickering, A.D.. 1995 Sexual maturity modifies the responsiveness of the pituitary-interrenal axis to stress in male rainbow trout. General and Comparative Endocrinology, 98 (3). 311-320.

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A significant reduction in stress-induced plasma cortisol levels is apparent in mature male rainbow trout compared to immature fish of both sexes and of the same age and strain. Mean plasma cortisol levels in groups of immature fish subjected to a standard 1h confinement stress were consistently higher (range 93.9 ± 4.9 - 114.8 ± 4.1 ng ml-1) than mean levels in mature males exposed to the same procedure (range 47.0 ± 4.3 - 71.7 ± 5.7 ng ml-1), throughout the 4 month period around spawning (p<0.001). Body weight was not found to be a significant determinant of post-stress cortisol level. The dissimilarity in plasma cortisol levels between mature and immature fish following confinement does not stem from differences in the dynamics of the response; during a 24h period of confinement the rate of elevation of plasma cortisol levels was similar for both mature male and immature fish but mature male fish attained a significantly lower peak cortisol level (51.6 ± 5.2 ng ml-1) than immature fish (89.5 ± 7.7 ng ml-1), a disparity which was maintained throughout the period of stress (p<0.05 - p<0.001). The reduced responsiveness of the interrenal tissue of mature male fish during stress appears to be modulated by the hypothalamus/pituitary. Plasma ACTH levels in mature male trout (44 ± 9 pg ml-1) are significantly lower than those of immature fish (71 ± 9 pg ml-1, p<0.01) within 30 min of the onset of confinement and remain so during a 3h period of confinement. These data suggest that the cortisol/ACTH feedback equilibrium has been modified in mature fish, to a lower "set point". Furthermore, although stress caused a significant decline of plasma α-MSH levels in both immature fish and mature males, N-acetyl-β-endorphin levels were reduced only in mature male fish during confinement stress.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Other
UKCEH and CEH Sections/Science Areas: _ Pre-2000 sections
ISSN: 0016-6480
Additional Keywords: stress, sexual maturity, rainbow trout, Oncorhynchus mykiss, cortisol, ACTH, MSH, endorphin
NORA Subject Terms: Zoology
Biology and Microbiology
Date made live: 13 Jul 2015 10:52 +0 (UTC)

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