Adult-born neurons continue growth even after neurogenesis decline, outgrowing neonatally-born neurons

A recent study publicized in the journal JNeurosci found that adult-born neurons continue with growth and aiding in brain flexibility even after neurogenesis declines.

The Canadian-based study was published in support of the Natural Sciences and Engineering Research Council of Canada, the Canadian Institutes of Health Research and the Michael Smith Foundation for Health Research.

“It is generally assumed that by 2 months of age adult-born neurons are mature and equivalent to the broader neuronal population, raising questions of how they might contribute to hippocampal function in old age when neurogenesis has declined,” the study reads.

“However, few have examined adult-born neurons beyond the critical period, or directly compared them to neurons born in infancy. Here, we used a retrovirus to visualize functionally-relevant morphological features of 2- to 24-week-old adult-born neurons in male rats,” it states.

The research team administered to rodents’ dentate gyri a retrovirus which establishes itself with the DNA of dividing cells, making the neurons born on injection day glow.

The adult-born neurons underwent a development span of six weeks, in which growth markers reappeared as the neurons kept growing. By 24 weeks after birth, the adult-born neuros overgrew the infancy-born neurons, with researchers uncovering an increase in dendrites and possible synapses and larger synaptic terminals.

“Compared to neonatally-born neurons, old adult-born neurons had greater spine density, larger presynaptic terminals, and more putative efferent filopodial contacts onto inhibitory neurons,” according to the findings.

“By integrating rates of cell birth and growth across the lifespan, we estimate that adult neurogenesis ultimately produces half of the cells and the majority of spines in the dentate gyrus. Critically, protracted development contributes to the plasticity of the hippocampus through to the end of life, even after cell production declines.”

“Persistent differences from neonatally-born neurons may additionally endow adult-born neurons with unique functions even after they have matured,” the research team concluded in their findings.

Image courtesy of Shutterstock
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