Survival and Axonal Outgrowth of the Mauthner Cell Following Spinal Cord Crush Does Not Drive Post-injury Startle Responses

Frontiers in Cell and Developmental Biology, 2021 · DOI: 10.3389/fcell.2021.744191 · Published: November 19, 2021

Simple Explanation

This study investigates the role of Mauthner cells (M-cells) in the recovery of startle responses in adult goldfish after spinal cord injury. M-cells are known to initiate fast startle responses in fish. The research examines whether the regrowth of M-cell axons contributes to the return of startle behavior after spinal cord crush. They looked at the morphological, behavioral, and electrophysiological consequences of M-cell axotomy. The study found that while M-cells survive, regrow axons, and maintain some connections, they don't seem to play a major role in the return of startle responses after spinal cord injury. Other neurons may be more important.

Study Duration

198–468 days

Participants

Adult goldﬁsh, Carassius auratus

Evidence Level

Original Research

Key Findings

1
M-axons can survive for at least 468 days (∼1.3 years) after spinal cord crush, maintain regrowth, and elicit putative trunk EMG responses.
2
M-axon sprouts project caudally, crossing the wound site after SML-crush, but they do not play a substantive role in post-injury startle responses.
3
Post-injury startle responses occur even in the absence of M-cells, indicating that other neuronal circuits are responsible for the recovered behavior.

Research Summary

This study investigates the role of Mauthner cells (M-cells) in post-injury startle responses following spinal cord crush in adult goldﬁsh. The researchers examined the morphological, behavioral, and electrophysiological consequences of M-cell axotomy. The findings indicate that although M-cells survive, maintain regrowth, and retain supraspinal connections, they do not play a substantial role in the emergence of acoustic/vibratory-triggered responses after spinal cord injury. The study suggests that alternative neuronal pathways are responsible for the recovery of startle behavior. This highlights the need for multidisciplinary approaches to understand complex neural circuit functions and their disturbances.

Practical Implications

Regenerative strategies

Future research should focus on identifying and targeting alternative neuronal pathways that contribute to the recovery of motor behaviors after spinal cord injury, rather than solely focusing on M-cells.

Understanding Neural Circuitry

Further investigation into the specific neurons and circuits involved in post-injury startle responses is needed to develop targeted therapies.

Aberrant pathway choice

Understanding the mechanisms that lead to aberrant pathway choices in regenerating axons could help improve functional recovery by guiding axons to appropriate targets.

Study Limitations

1
The experimental approach provides only 'snapshots' at specific postoperative intervals, limiting the ability to observe the dynamic remodeling of M-axon sprouts over time.
2
The study focuses on adult goldfish, and the findings may not be directly applicable to other species or developmental stages.
3
The precise neuronal circuitry responsible for post-injury startle responses remains unidentified, limiting the ability to fully understand the compensatory mechanisms.

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