Clear chemical connection between physical activity and brain health

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"... Now, scientists have shown in cell studies that the connection may be more direct, which opens the door to more targeted physical therapies for brain health and potential treatment of neurodegenerative conditions. ...
The scientists ... were able to demonstrate through mice muscle cells how their contraction caused hippocampal neurons to fire off larger and more frequent electrical signals. Within days, these stronger and healthier signals became more synchronized, mimicking neural organization in the brain. ..."

"... To isolate the chemicals released by contracting muscles and test them on hippocampal neurons, the researchers collected small muscle cell samples from mice and grew them in cell culture dishes in the lab. When the muscle cells matured, they began to contract on their own, releasing their chemical signals into the cell culture.

The research team added the culture, which now contained the chemical signals from the mature muscle cells, to another culture containing hippocampal neurons and other support cells known as astrocytes. Using several measures, including immunofluorescent and calcium imaging to track cell growth and multi-electrode arrays to record neuronal electrical activity, they examined how exposure to these chemical signals affected the hippocampal cells.

The results were striking. Exposure to the chemical signals from contracting muscle cells caused hippocampal neurons to generate larger and more frequent electrical signals — a sign of robust growth and health. Within a few days, the neurons started firing these electrical signals more synchronously, suggesting that the neurons were forming a more mature network together and mimicking the organization of neurons in the brain. ...
“Ultimately, our research may contribute to the development of more effective exercise regimens for cognitive disorders such as Alzheimer's disease,” ..."

From the highlights and abstract:

"Highlights

• Contracting muscle media enhances hippocampal neuronal activity.

• Contracting muscle media expedites synaptic maturation.

• Contracting muscle media accelerates accumulation of filamentous actin at synapses.

• Contracting muscle media induces significant astrocyte and neuron proliferation.

• Astrocytes release factors that inhibit muscle media-induced neuronal activity.

Abstract

Exercise supports brain health in part by enhancing hippocampal function. The leading hypothesis is that muscles release factors when they contract (e.g., lactate, myokines, growth factors) that enter circulation and reach the brain where they enhance plasticity (e.g., increase neurogenesis and synaptogenesis). However, it remains unknown how the muscle signals are transduced by the hippocampal cells to modulate network activity and synaptic development. Thus, we established an in vitro model in which the media from contracting primary muscle cells (CM) is applied to developing primary hippocampal cell cultures on a microelectrode array. We found that the hippocampal neuronal network matures more rapidly (as indicated by synapse development and synchronous neuronal activity) when exposed to CM than regular media (RM). This was accompanied by a 4.4- and 1.4-fold increase in the proliferation of astrocytes and neurons, respectively. Further, experiments established that factors released by astrocytes inhibit neuronal hyper-excitability induced by muscle media, and facilitate network development. Results provide new insight into how exercise may support hippocampal function by regulating astrocyte proliferation and subsequent taming of neuronal activity into an integrated network."

Clear chemical connection between physical activity and brain health

Exercise releases chemical signals that boost brain health Beckman researchers studied how chemical signals from contracting muscles promote healthy brains. Their findings reveal how these signals help grow and regulate new brain networks while also pointing toward ways of improving brain health through exercise.

Astrocyte-mediated Transduction of Muscle Fiber Contractions Synchronizes Hippocampal Neuronal Network Development (no public access)

Hippocampal neurons (yellow) surrounded by astrocytes (green) in a cell culture from the study.