Neurons Produced During Adulthood React To Stimuli

AMHERST, Mass. - Brain cells that are produced in adult mammals respond to sexual stimuli, according to a team of biologists at the University of Massachusetts. Liyue Huang, a postdoctoral researcher, Benjamin Lawrence, an undergraduate student, and Eric Bittman, a biology professor who is affiliated with the University's neuroscience and behavior program, will present the research at the meeting of the Society for Neuroscience in Miami, Fla., Oct. 23-28.

Until recently, it was believed that production of neurons in mammals ceased soon after birth. However, research within the past decade has shown that adult mammals do, in fact, continue to produce these cells. But the function of neurons produced after birth - and whether they manage to hook properly into the brain's complex circuitry at all - was unclear. The team's research suggests that these cells are activated during sexual behavior, providing the first direct evidence that brain cells produced in adulthood may function in a naturally occurring behavior, Bittman said.

Scientists had previously determined that adults produce new brain cells in two regions of the forebrain. Many of these neurons migrate to another portion of the brain called the olfactory bulb, which allows animals to sense and identify odors. Many neurons in this region respond to the stimulation of sexual activity.

The team made the determination by combining two techniques: one which allows scientists to "tag" individual cells that have been produced at a certain time and track them, much as wildlife experts track specific animals; and another which essentially takes a chemical "snapshot" of the neuron while it's active. Neurons with both markers are adult-produced brain cells that work in response to sexual activity.

"If there's to be clinical relevance for patients suffering from stroke, or brain injuries, it's not enough just to have new cells produced," said Bittman. "You need to know if the cells are actually working." Although the research was conducted on hamsters, scientists hope that this insight into how neurons are produced, and how they behave, may be a step toward new treatments for disorders such as Alzheimer's disease, Parkinson's disease, and stroke, which are related to the premature death or dysfunctioning of neurons.

The next step, Bittman says, is to determine whether neurons produced during adulthood respond only to sexual stimuli, and if so, which are the critical cues provided by the female. Scientists are also examining whether the neurons are triggered by other stimuli, including the scent of a female, the scent of an aggressive male, and a non-social odor such as peppermint.