title: Effect of ageing on melatonin synthesis induced by 5-hydroxytryptophan and constant light in rats.
abstract: 1. This paper describes the effect of the serotonin precursor 5-hydroxytryptophan (5-HTP) on pineal melatonin synthesis young and old rats. 2. 5-HTP itself increased pineal melatonin levels in old rats but did not change melatonin concentrations in young rats kept under 12 hr/12 hr light/dark conditions. 3. After continuous exposure to light for 72 hrs, 5-HTP induced a significant increase in melatonin levels in young rats but did not change the 5-HTP effect on melatonin in old animals. 4. These results are discussed in consideration of previous reports of altered beta-receptor up-regulation by light in old animals, and suggest that the age-related decrease in melatonin synthesis is not entirely related to changes of the enzymatic machine for melatonin synthesis.
authors.affiliation: Department of Psychiatry, University of Melbourne, Vic., Australia.
authors.forename: I M
authors.initials: IM
authors.lastname: McIntyre
authors.forename: G F
authors.initials: GF
authors.lastname: Oxenkrug
mesh_terms: D006916:5-Hydroxytryptophan / Q000494:pharmacology*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D008027:Light; D008297:Male; D008550:Melatonin / Q000096:biosynthesis*; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D006916:5-Hydroxytryptophan; D008550:Melatonin