EFFECTS OF PHOTOPERIOD AND DIFFERENT INTENSITIES OF LIGHT EXPOSURE ONMELATONIN LEVELS IN THE BLOOD, PINEAL ORGAN, AND RETINA OF THE BROOK TROUT (SALVELINUS-FONTINALIS MITCHILL)

Citation
A. Zachmann et al., EFFECTS OF PHOTOPERIOD AND DIFFERENT INTENSITIES OF LIGHT EXPOSURE ONMELATONIN LEVELS IN THE BLOOD, PINEAL ORGAN, AND RETINA OF THE BROOK TROUT (SALVELINUS-FONTINALIS MITCHILL), Canadian journal of zoology, 70(1), 1992, pp. 25-29
Citations number
34
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Zoology
Journal title
ISSN journal
0008-4301
Volume
70
Issue
1
Year of publication
1992
Pages
25 - 29
Database
ISI
SICI code
0008-4301(1992)70:1<25:EOPADI>2.0.ZU;2-S
Abstract
Daily variations in the melatonin concentration in the blood, pineal o rgan, and retina of the brook trout, Salvelinus fontinalis, were inves tigated in July under constant photoperiod (16 h L : 8 h D) and temper ature (12-degrees-C). Diel variations in melatonin levels in the blood and pineal organ showed similar patterns, with higher values during t he night, whereas melatonin concentrations in the retina increased sli ghtly in the first half of the light period. Light exposure of 1 h dur ation at mid-dark decreased melatonin levels in the blood and pineal o rgan in an intensity-dependent manner, whereas retinal melatonin level s increased with increasing light intensities. The minimum light inten sity causing significant effects on the melatonin concentrations was 2 lx for the serum and 20 lx for the pineal organ and the retina. The p arallelism between pineal and circulating melatonin patterns suggests that the lateral eyes of the trout have no significant endocrine funct ion as far as the melatonin rhythm in the blood is concerned. Supporti ng evidence comes from the reversed response of retinal melatonin to l ight exposure at mid-dark, and from the low retinal melatonin concentr ations found in this study. Thus, the serum melatonin rhythm of the br ook trout seems to be mainly the result of rhythmic melatonin secretio n from the pineal organ.