[Age-related characteristics of the effects of epithalamin on serotonin metabolism in the pineal gland of rats].

The biosynthesis of serotonin into melatonin was decreased in old (18-20-month) in comparison to young (4-5-month) male Wistar rats. 5-day morning injections to young and old rats with polypeptide pineal preparation (epithalamin) in a dose of 2.5 mg/kg of body weight induced the increase in the night peak of serotonin, N-acetylserotonin and melatonin in young and melatonin alone in old rats and did not influence 5-methoxytryptamine, 5-oxy- and 5-methoxyindoleacetic acids level. These data support suggestion of ultrashort loop between pineal peptides and indoles and that epithalamin increases the metabolism of serotonin into melatonin.