Food deprivation and refeeding effects on pineal indoles metabolism and melatonin synthesis in the rainbow trout Oncorhynchus mykiss

Fasted rainbow trout exhibited reduced melatonin levels throughout a 24-hour cycle, associated with decreased enzyme activity.

• Pineal melatonin levels and the activity of the enzyme responsible for its production showed daily variations, peaking at night.
• Food deprivation for 7 days led to lower melatonin content and decreased enzyme activity in trout.
• In fasted fish, levels of serotonin and its metabolite, 5-HIAA, increased at night but did not change significantly during the day.
• Circulating melatonin levels were lower at midday in food-deprived trout, but not at night.
• Refeeding for 5 days generally counteracted the effects of fasting on melatonin levels.
• Cortisol levels in plasma decreased after food deprivation and remained low after refeeding.

AI simplified