They noted that the breakthrough raises hopes that it might one day be possible to develop an anti-aging drug for humans.
The researchers gave a mixture of two natural chemicals, available in health food stores, to the animals.
The chemicals used were acetyl-L-carnitine and alpha-lipoic acid, both of which are normally found in the body's cells.
Acetyl-L-carnitine is sold as an energy-booster and alpha-lipoic acid as an antioxidant with anti-aging effects, the BBC said.
Lead researcher, Dr Bruce Ames, of the University of California at Berkeley, noted that the brains of the rats, in the equivalent of their seventies, looked better and the animals had more energy.
In addition, the rats' memories were significantly improved.
The researchers estimated that the effect on the rats was the equivalent to making a 75- to 80-year-old person act middle-aged.
The BBC added that the University of California has now patented the combination of the two chemicals, and human trials have already commenced.
Three papers on different animal studies of the chemicals have been published in the journal Proceedings of the National Academy of Sciences.
| The supplements' effect was equivalent to making a 75- to 80-year-old person act middle-aged.
The studies assessed the biochemical action of the supplements, compared the behavior of old and young rats, and tested the memory of animals fed the compounds.
The researchers found that the two chemicals in combination had a positive impact on mitochondria.
Mitochondria generate energy within the cells, and research has suggested that their deterioration is an important cause of aging, commented the BBC.
When the mitochondria produce energy they also generate free radicals.
The supplement combination was found to mop up these free radicals in the mitochondria, the BBC reported.
In addition, it enhanced the activity of an enzyme essential to the production of energy.
Furthermore, the BBC said that, in animals fed the compounds, radicals damaged the mitochondria in brain cells, important to memory, less.