Pheromones trigger brain cell growth, say researchers

Pheromone signals from dominant males spark new brain cells in their female partners and could help repair injured brains, suggests a new study by a University of Calgary neuroscientist.

Sam Weiss's findings, in the July issue of the journal Nature Neuroscience, provide evidence that pheromones — subtle chemical signatures that influence mating behaviour — can control stem cells in the brain.

The study also shows that in females, two brain areas that affect memory and smell work together in developing a pheromonal bond with the desired male.

"It turns out that those two regions are also regions where new neurons are added throughout the lifetime of all mammals, including humans," said Weiss, director of the university's Hotchkiss Brain Institute.

In his research, Weiss exposed female mice to the scent of the alpha male, and found newly generated neurons in the hippocampus and olfactory bulb — the seats of memory and smell, respectively.

The scent of a subordinate male did not stimulate brain cell growth.

After two weeks, when presented with a group of males, the female was better able to recognize the dominant male's scent.

By blocking brain cell production, Weiss found females were no longer able to link the scent with its owner.

"If you stop the production of brain cells, would you stop [this recognition] down the road?" asked Weiss. "That's exactly what we found."

Explanation for brain stem cells

Weiss believes his research helps explain why humans have stem cells in their brains.

"Nobody actually ever understood why those two regions of the brain are ones that add brain cells in such increasing numbers," he said.

"Reproductive success, and the health of relationships and offspring is critical for the survival of any species, so if stem cells are going to play a role, they should be playing a role in ensuring success in health."

Weiss found pheromonal signals act to increase levels of prolactin and luteinizing hormone in the brain, triggering the growth of new neurons from neural stem cells.

He hopes an improved knowledge of this process will allow researchers to harness stem cells for repairing brain injuries.

"Hormones may be natural boosters of brain cell production," said Weiss. "The hormones themselves may be the critical parts of turning brain cells on [and] we're starting to test whether the hormones could actually be a part of repair processes."