The most exciting finding of the Pierpaoli-Regelson lifespan experiments is that both melatonin and pineal transplants were able to achieve significant prolongation of life and vigor, as well as organ rejuvenation in aging animals. Since most of us are already older than we'd like to be, it's encouraging to see evidence that a therapy can produce anti-aging and rejuvenation effects in middle-aged animals.
Can Melatonin Really Extend Maximum Lifespan?
Although the melatonin-treated animals in the Pierpaoli-Regelson experiments lived significantly longer than the control animals, the question of whether melatonin can extend maximum lifespan is still open to question because none of the controls or the treated animals reached their maximum lifespan potential (MLP) for the strain of mice under scrutiny. In the case of the C57BL/6 mice, the MLP for untreated animals is about 40 months, but none of the melatonin treated animals lived beyond 29 months. In the case of the BALB/6 mice, the MLP is about 36 months, but none of the melatonin-treated animals lived beyond 31 months. And in the case of the NZB mice, the melatonin-treated animals did reach their MLF: but the strain itself has been genetically bred to die prematurely from auto immune disease.
Larger Study Needed
However, the fact that most of the melatonin-treated animals failed to reach their maximum lifespan potential is not surprising because MLP represents the longest possible lifespan of a strain of mice under ideal living conditions, and it's extremely rare for laboratory animals to come close to this ideal. Since there were relatively few mice in the Pierpaoli-Regelson studies, and since their living conditions may not have been ideal, the results are far from definitive. What's needed is a larger study of the effects of melatonin on maximum lifespan in which the experimental animals are maintained under the best possible conditions. Such a study would help us learn a great deal more about melatonin's ability to slow aging and extend lifespan.
Other Pineal Hormones
Another unanswered question is whether other pineal hormones might add to melatonin's anti-aging effects. Since the animals receiving pineal transplants did even better than the melatonin-treated animals, in spite of the trauma of the operation, it seems reasonable that other hormones produced by the pineal gland may also be involved in aging in addition to melatonin. At least one of these hormones -- epithalamin -- has been identified, characterized, and used in experiments (in Russia) to extend the lifespan of laboratory animals. It would be interesting to determine if the combination of melatonin and epithalamin extends lifespan more than just melatonin.
Melatonin Improves Immune Function