title: Aging and diurnal rhythms of pineal serotonin, 5-hydroxyindoleacetic acid, norepinephrine, dopamine and serum melatonin in the male rat.
abstract: Pineal serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), norepinephrine (NE) and dopamine (DA) were measured by high-pressure liquid chromatography with electrochemical detection and serum melatonin was measured by radioimmunoassay in rats aged 3 weeks, 8 weeks and 18 months. They were killed either at mid-light or mid-dark of a 12 h light:12 h dark cycle. Diurnal rhythms were observed for 5-HT and 5-HIAA in all ages studied while those for NE and DA were not observed in the 18-month-old animals. Pineal 5-HT and 5-HIAA were higher in 3-week-old rats at mid-dark, and lower at mid-light than in older animals. The pineal content of NE was lower in the 3-week-old rats at mid-dark and mid-light compared with that in the 8-week-old while the DA content was lower at mid-dark. In addition, pineal 5-HT, 5-HIAA, NE and DA were lower in the 18-month-old than in the 8-week-old animals at mid-dark. At mid-dark serum melatonin levels showed an age-related decrease. This study shows that an age-related decrease of pineal 5-HT, 5-HIAA, NE and DA can only be demonstrated at mid-dark and that the age-related decrease of melatonin may not be due to a decrease in sympathetic activity.
authors.forename: F
authors.initials: F
authors.lastname: Tang
authors.forename: M
authors.initials: M
authors.lastname: Hadjiconstantinou
authors.forename: S F
authors.initials: SF
authors.lastname: Pang
mesh_terms: D000375:Aging; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D002940:Circadian Rhythm; D004298:Dopamine / Q000032:analysis; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D008297:Male; D008550:Melatonin / Q000097:blood*; D009638:Norepinephrine / Q000032:analysis; D010870:Pineal Gland / Q000032:analysis*; D011863:Radioimmunoassay; D051381:Rats
chemical_list: D006897:Hydroxyindoleacetic Acid; D008550:Melatonin; D004298:Dopamine; D009638:Norepinephrine