Thyroid function and olfactory responses to L-alanine during induced smoltification in Atlantic salmon, Salmo salar

1997 ◽  
Vol 54 (3) ◽  
pp. 596-602 ◽  
Author(s):  
P -P Morin ◽  
T J Hara ◽  
J G Eales
Keyword(s):  
Thyroid Hormone ◽  
Atlantic Salmon ◽  
Olfactory Bulb ◽  
Salmo Salar ◽  
Olfactory Epithelium ◽  
Eeg Activity ◽  
Olfactory Responses ◽  
Full State ◽  
Thyroid Hormone Levels ◽  
State Plasma

For 5 weeks starting in mid-February we examined developmental correlations between external smolt features, plasma thyroid hormone levels, and olfactory responses in Atlantic salmon transferred from 0.9 to 11°C and exposed to a 16 h light : 8 h dark (16L) or an 8 h light : 16 h dark (8L) photoperiod. In 16L fish, external smolt features developed to 80% of full state, plasma L-thyroxine (T4) surged at week 3, but there were no changes in plasma 3,5,3 prime -triiodo-L-thyronine, olfactory bulb electroencephalographic (EEG), or olfactory epithelium electro-olfactographic (EOG) activities in response to nasal stimulation with L-alanine (10-9 to 10-5 M). In 8L fish, external smolt features were arrested at 40% of full state, plasma T4 showed no surge, EOG activity increased modestly, but EEG activity increased markedly at weeks 3 and 4. Thus, under the particular photoperiod and temperature conditions imposed in this study in February and March, enhanced olfactory activity can develop in premigratory Atlantic salmon independently of external smolt features or a significant surge in plasma T4.

T4 depresses olfactory responses to L-alanine and plasma T3 and T3 production in smoltifying Atlantic salmon

1995 ◽  
Vol 269 (6) ◽  
pp. R1434-R1440 ◽  
Author(s):  
P. P. Morin ◽  
T. J. Hara ◽  
J. G. Eales
Keyword(s):  
Atlantic Salmon ◽  
Olfactory Bulb ◽  
Olfactory Epithelium ◽  
High Plasma ◽  
Outer Ring ◽  
Olfactory Responses ◽  
Stimulation Of

During natural or induced smoltification, Atlantic salmon exhibit spring elevations in olfactory activity and plasma L-thyroxine (T4). To determine whether T4 influences olfactory activity, we administered T4 to late parr in early April and measured olfactory bulb electroencephalogram and olfactory epithelium electroolfactorogram responses to L-alanine nasal stimulation, plasma T4 and 3,5,3'-triiodo-L-thyronine (T3) levels, and hepatic and brain monodeiodination. T4 treatment raised plasma T4 to 15 ng/ml, simulating the smolt T4 surge, and depressed plasma T3 and electroencephalogram responses, without modifying electroolfactorogram responses. Decreased plasma T3 may be explained by inhibition of hepatic T4 outer-ring deiodination, generating T3, and stimulation of inner-ring deiodination, degrading T4 and T3. Brain T4 outer-ring deiodination was also strongly inhibited. In conclusion, creation of a high plasma T4 concentration simulating the natural smolt peak depressed olfactory bulb responses to L-alanine due to the high T4 concentration or the depressed T3 availability in brain induced by T4. T4 may terminate the period of heightened olfactory responsiveness during smoltification.

Electrical Responses of the Olfactory Epithelium of Atlantic Salmon (Salmo salar)

1971 ◽  
Vol 28 (4) ◽  
pp. 565-572 ◽  
Author(s):  
A. M. Sutterlin ◽  
N. Sutterlin
Keyword(s):  
Amino Acids ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Olfactory Epithelium ◽  
Spike Activity ◽  
Olfactory Mucosa ◽  
Oscillatory Activity ◽  
Atlantic Salmon Salmo Salar ◽  
Low Concentrations ◽  
Complex Solutions

Multiunit spike activity was recorded from the olfactory mucosa of Atlantic salmon (Salmo salar) using metal-filled glass microelectrodes. A number of simple and complex solutions were tested for stimulatory effectiveness. Amino acids as a class of compounds were highly stimulatory; little or no response was obtained to a variety of simple sugars, n-aliphatic acids, alcohols, or amino-substituted alcohols. An increase in asynchronous spike activity was evoked by low concentrations of amino acids and oscillatory activity was evoked by higher concentrations of amino acids. Brief treatment of the epithelium with dilute solutions of HgCl2 blocked the chemosensitivity of the receptors.

Thyroid hormone levels in flow-challenged adult salmon (Salmo salar L.)

1989 ◽  
Vol 67 (8) ◽  
pp. 1851-1855 ◽  
Author(s):  
A. F. Youngson ◽  
H. A. McLay
Keyword(s):  
Thyroid Hormone ◽  
Steroid Hormones ◽  
Salmo Salar ◽  
Water Velocity ◽  
Male Fish ◽  
Hormone Levels ◽  
Thyroid Hormone Levels ◽  
Circulating Levels

Circulating levels of thyroid and steroid hormones in salmon (Salmo salar) that had spent one winter in seawater have been determined in fish at rest and after a 4-h exposure to increased water velocity. The responses of fish of both sexes to this challenge were examined in April and June, while the fish were in seawater; sexually maturing males only were examined in freshwater in August and November. Mean thyroxine levels in resting controls ranged from 8.8 to 15.2 ng/mL. Mean thyroxine levels in challenged fish were significantly greater on each occasion. In male fish, 11-oxotestosterone levels were reduced after challenge, while androstenedione levels in females remained unchanged. In April, thyroxine levels after challenge were correlated with 11-oxotestosterone levels in males and with androstenedione levels in females.

Atlantic salmon, Salmo salar L., and Arctic char, Salvelinus alpinus (L.): comparative correlation between iodine-iodide supplementation, thyroid hormone levels, plasma cortisol levels, and infection intensity with the sea louse Caligus elongatus

1999 ◽  
Vol 77 (7) ◽  
pp. 1092-1101 ◽  
Author(s):  
A Mustafa ◽  
B M MacKinnon
Keyword(s):  
Thyroid Hormone ◽  
Atlantic Salmon ◽  
Plasma Cortisol ◽  
Infection Intensity ◽  
Arctic Char ◽  
Sea Lice ◽  
Lower Plasma ◽  
Hormone Levels ◽  
Thyroid Hormone Levels ◽  
Cortisol Levels

The interrelationship between plasma cortisol levels, iodine-iodide nutritional supplementation, plasma thyroid hormone levels (tri- and tetra-iodothyronine, T3 and T4 respectively), and infection intensity with the sea louse Caligus elongatus were investigated in Atlantic salmon, Salmo salar L., and Arctic char, Salvelinus alpinus (L.). Cortisol-implanted Atlantic salmon had significantly higher mean intensities of sea lice than salmon not implanted with cortisol. Untreated Arctic char had significantly higher plasma cortisol levels and sea lice infections than untreated salmon. Cortisol-implanted salmon had lower plasma levels of T3 and T4. Salmon and char treated with iodized feed and iodinated water had higher plasma T3 and T4 levels, higher plasma T3/T4 ratios, and lower plasma cortisol levels than controls. Sea lice infections were significantly reduced on salmon treated with either iodized feed (P < 0.05) or iodinated water (P < 0.05). Char treated with iodized feed also had significantly reduced infections (P < 0.05). In general, iodized feed had a greater effect than iodinated water in reducing sea lice numbers. This study indicates that elevated plasma cortisol levels in salmon and char result in lower plasma levels of thyroid hormone and an increased susceptibility to sea lice infections. It is concluded that providing the fish with sufficient iodine-iodide increases thyroid hormone levels, reduces plasma cortisol levels, and reduces susceptibility to sea lice infections.

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