Effects of long-term administration of melatonin and a putative antagonist on the ageing rat.

Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.

Adult rats were treated with either melatonin, the putative melatonin antagonist N-(2,4 dinitrophenyl)-5-methoxytryptamine (ML-23), their combination, or a vehicle for 16 months via the drinking water. The survival rates, serum testosterone and densities of 125I-melatonin binding sites in the medulla-pons and hypothalamus of the animals at the age of 27-29 months were significantly higher in the melatonin than vehicle-treated group. Surprisingly, ML-23 without or with melatonin, also prolonged the life-span of the aged animals. ML-23 treatment greatly increased 125I-melatonin binding in the medulla-pons whereas this increase was prevented by melatonin supplementation. Thus melatonin can attenuate age-related decrease in survival rates, testosterone and brain 125I-melatonin binding sites, while chronic blockade by the putative antagonist also elicits melatonin-mimetic responses, perhaps by effecting supersensitivity.

PMID: 7605949 [PubMed - indexed for MEDLINE]