How Long Does a Neuron Live?

Is the lifespan of a neuron proportional to the lifespan of its species?

While biologists know the average expectation of life of most of the cells of our body, they have not yet discovered the average lifetime of neurons. The main reason for this lies in the fact that neurons are not able to reproduce. Recently, an Italian team of researchers wanted to verify whether the average lifetime of a neuron is (or is not) proportional to the average lifetime of the species to which it belongs.

In order to further investigate this, the scientists transplanted neurons obtained from mice embryos (genetically modified in such a way that they could be easily spotted through the production of a fluorescent protein) into the brains of rats. A mouse lives about 1.5 years, while a rat can live up to 3 years. So if neurons have an average life proportioned to the average lifetime of the species it belongs, one should not expect to find traces of them in brain of rats after 1.5 years.

However, the results of this study, published by the Journal Proceedings of the National Academy of Sciences of the United States of America, have shown with great surprise that, after 1.5 years, the fluorescent transplanted neurons were still present in the brain of rats. This shows that the average lifetime of neurons does not depend on the average lifetime of the species it belongs to.

And what’s more; while aging, neurons lose connections among them, called synapses, with a velocity that depends on the species. In addition, the researchers have shown that neurons transplanted into the brains of rats lose connections with a velocity that is more similar to the one of rats, then to the one of mice. Hence “neurons are ageless” and their health is highly influenced by the conditions in which they live.

Reference:
Magrassi L, Leto K, & Rossi F (2013). Lifespan of neurons is uncoupled from organismal lifespan Proceedings of the National Academy of Sciences of the United States of America DOI: 10.1073/pnas.1217505110