The secret to vampires’ longevity may be out, after researchers announced that injecting old mice with blood plasma from human teenagers rejuvenated their brains, increasing their cognitive capacities while also restoring some of their youthful energy.

Presenting their findings at the annual meeting of the Society for Neuroscience in San Diego earlier this week, scientists from a firm called Alkahest described how they injected blood samples from 18-year-old humans into 12-month-old mice, which is the equivalent of 50 human years.

Prior to the experiment, the mice had been exhibiting signs of old age, achieving lower scores on memory and cognition test than sprightlier rodents, while also moving more slowly.

Yet after receiving the injections, they began to run around with the same vigor as three-month-old mice, New Scientist reports. Their memory improved too, and they began to outperform untreated mice on tests that required them to learn and remember their way around a maze.

Blood plasma is the liquid in which blood cells are suspended, and also contains minerals, salts, and a number of proteins. While Alkahest’s researchers say they have identified some of the proteins in young plasma that are responsible for this rejuvenating effect, they are remaining tight-lipped for now over which ones they are.

Yet they are willing to reveal that the plasma injections stimulated neurogenesis, meaning new neurons were born in the brains of these mice. All of these new brain cells were located in the hippocampus, which plays a major role in the formation of memories.

The team therefore believe that blood plasma from young donors may help to treat age-related cognitive decline and even Alzheimer’s disease, and have already begun a clinical trial to investigate whether or not this is indeed the case.