Israeli scientists have just reported the results of a new lifespan study with melatonin in aging rats (NeuroReport, 6, 785-788, 1995). This study reINFOrces earlier lifespan studies with several strains of mice (see "Evidence That Melatonin Is An Anti-Aging Therapy").
The scientists used male CD rats, 11-13 months old in their study. These rats have a maximum lifespan of 30-35 months, with 20% mortality at 20-25 months.
In addition to the effect of melatonin (in the drinking water) on the lifespan of these rats, they also sought to determine if melatonin could counteract the decrease in melatonin binding sites in the rat brain.
Results Of Study The study was conducted for 15-16 months, after which the animals were sacrificed and their brains tested. The scientists found that supplemental melatonin:
"...markedly increased the number of rats which survived to the age of 26-29 months... 43% of the control group of 16 animals survived to the age of 27-29 months... which is in agreement with the life expectancy of this species. Of the melatonin-treated group of 15 animals 87% survived to the age of 27-29 months. In the control group, 5 of the 7 survivors suffered from severe pneumonia whereas the melatonin-treated animals either did not suffer from pneumonia, or had very weak symptoms."
The scientists also found that there was a 54%-to-115% increase in melatonin binding sites in the brains of the melatonin-treated animals depending upon which binding site they looked at, and that the treated animals had higher circulating testosterone levels than the controls. This rejuvenation effect may have been one of the reasons for the extended lifespan of the melatonin-treated rats.