Michigan State University Scientists Analyze Brain Cells Born During Puberty With Neurolucida
What does it take to survive that tumultuous time called adolescence? Good friends, exercise, and new brain cells.
Scientists at Michigan State University found evidence of neurogenesis in the brains of adolescent hamsters, according to a study published last month in PNAS. The new cells, which became integrated into neural circuits in adulthood, were discovered in the amygdala and connected limbic regions – areas associated with social learning and mating behavior.
Working in Dr. Cheryl Sisk’s lab, neuroscience graduate student Margaret Mohr studied male Syrian hamsters. To identify new cells, she injected fourteen animals with the cell birthdate marker bromodeoxyuridine (BrdU) throughout puberty (postnatal day 28 – 49). Half the hamsters were housed in cages equipped with running wheels and comfortable nests (enriched environment), while the other half were kept in unembellished cages to test the effect of an enriched environment on cell survival. Once the hamsters reached adulthood, they were allowed to mate with female hamsters, then euthanized an hour later.
To see how the pubertally born cells fared in adulthood, Mohr and Sisk analyzed Nissl-stained brain sections. They used Neurolucida to trace regions of interest and quantify Fos-labeled and BrdU-labeled cells to determine if enrichment enhanced the survival of pubertally born cells, and to count the number of the afore-mentioned cells that had been active during sociosexual behavior in adulthood.
“Neurolucida made my analyses efficient and consistent,” Mohr said.
According to the paper, three-fourths of pubertally born cells in the dentrate gyrus became mature neurons or astrocytes, while in the amygdala and hypothalamic regions, one-third of pubertally born cells developed into adult cells. After mating, approximately three percent of these cells expressed Fos, indicating that they were activated during sociosexual behavior and leading the authors to ascertain that they were involved in a brain circuit underlying male sexual behavior.
The researchers also found that, in some brain regions, an enriched environment increased the number of pubertally born cells that survived into adulthood.
“These results highlight the malleability and sensitivity to experience of the adolescent brain, and identify neurogenesis and gliogenesis as mechanisms that contribute to brain remodeling during this critical period of postnatal development,” the authors say.
Mohr, M. A., & Sisk, C. L. (2013). Pubertally born neurons and glia are functionally integrated into limbic and hypothalamic circuits of the male Syrian hamster. Proceedings of the National Academy of Sciences. doi:10.1073/pnas.1219443110