Emergence of Serotonergic Neurons After Spinal Cord Injury in Turtles

Front. Neural Circuits, 2018 · DOI: 10.3389/fncir.2018.00020 · Published: March 13, 2018

Spinal Cord Injury Neurology Neuroplasticity

Simple Explanation

This research explores how the spinal cord adapts after an injury, specifically looking at changes in serotonin-producing neurons in turtles. Serotonin is important for various spinal cord functions. The study found that after a spinal cord injury, the number of serotonin-producing cells increased in the spinal cord below the injury site. These new cells weren't newly born, but rather existing cells that changed their function. This change might be a way for the spinal cord to compensate for the loss of serotonin signals from the brain after the injury, potentially aiding in the functional recovery seen in turtles.

Study Duration

30 days

Participants

22 turtles (spinal cord-injured [ScI] = 16; ShI = 6)

Evidence Level

Not specified

Key Findings

1
Spinal cord injury (SCI) in turtles leads to an initial reduction in serotonergic innervation followed by an increase in serotonergic cells caudal to the lesion site after 30 days.
2
The newly emerged serotonergic neurons are not a result of cell proliferation but rather the respecification of existing post-mitotic cells.
3
The 5-HT1A receptor agonist (±)-8-Hydroxy-2-dipropylaminotetralin hydrobromide (8-OH-DPAT) blocked the increase in 5-HT+ cells, suggesting that 5-HT1A receptors may trigger the respecification process.

Research Summary

This study investigates the plasticity of the serotonergic system in turtles after spinal cord injury (SCI). It was hypothesized that SCI may trigger homeostatic changes in serotonergic innervation. The study found that after SCI, there was an initial decrease in serotonergic innervation, followed by an increase in the population of serotonergic cells caudal to the lesion site 30 days after the injury. These new serotonergic neurons are not newly born cells but rather post-mitotic cells that have changed their neurochemical identity. The 5-HT1A receptor may play a role in triggering this respeciﬁcation process.

Practical Implications

Understanding Spinal Cord Plasticity

The study provides insights into how the spinal cord can adapt and compensate for injury by altering the neurochemical identity of existing cells.

Potential Therapeutic Strategies

The findings suggest that targeting 5-HT1A receptors or promoting neurotransmitter respecification could be potential therapeutic strategies for spinal cord injury.

Evolutionary Perspective

The research highlights differences in spinal cord plasticity between mammals and non-mammalian vertebrates, offering a broader perspective on regenerative capabilities.

Study Limitations

1
The study was conducted on turtles, and the findings may not be directly applicable to mammals, including humans.
2
The specific mechanisms underlying neurotransmitter respecification and the role of other transcription factors need further investigation.
3
The functional consequences of the newly emerged serotonergic neurons and their contribution to locomotor recovery require further study.

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