Characterization of dendritic morphology and neurotransmitter phenotype of thoracic descending propriospinal neurons after complete spinal cord transection and GDNF treatment

Exp Neurol, 2016 · DOI: 10.1016/j.expneurol.2015.12.018 · Published: March 1, 2016

Spinal Cord Injury Neurology Neuroplasticity

Simple Explanation

After a spinal cord injury, the damaged nerve fibers in the central nervous system don't regenerate well, which limits how much function can be recovered. The limited recovery is thought to be due to changes in propriospinal neurons, particularly the descending ones (dPSNs). Compared to nerve fibers higher up in the spinal cord, dPSNs can regenerate better. This ability can be further improved by using a substance called glial cell line-derived neurotrophic factor (GDNF). This study used a modified rabies virus to look at the structure of dPSNs and also examined which neurotransmitters they use. The dPSNs were studied in animals with sham injuries, complete spinal cord cuts, or spinal cord cuts treated with GDNF.

Study Duration

4 days post-injury

Participants

24 Sprague Dawley adult female rats

Evidence Level

Not specified

Key Findings

1
dPSNs in animals without injury had dendrites mainly distributed in a top-bottom direction. Injury caused the dendrites to retract in this direction and extend sideways.
2
Treatment with GDNF increased the length of the ends of the dPSN dendrites, suggesting enhanced growth and connectivity.
3
Most of the dPSNs were found to use glutamate as their neurotransmitter, with smaller percentages using choline acetyltransferase (ChAT), glycine, or GABA.

Research Summary

This study characterized the dendritic morphology and neurotransmitter phenotype of thoracic descending propriospinal neurons (dPSNs) after spinal cord transection and GDNF treatment in adult rats. The researchers found that dPSNs exhibit remarkable dendritic and synaptic plasticity following spinal cord transection injury and GDNF treatment, indicating their potential for neural repair. The study also revealed that the majority of dPSNs projecting to the lumbar spinal cord are glutamatergic, with smaller populations expressing ChAT, glycine, and GABA.

Practical Implications

Therapeutic targets

The acute dendritic changes in dPSNs provide an early time window for therapeutic interventions to prevent dendritic atrophy and stimulate regenerative responses.

GDNF sensitivity

dPSNs are particularly sensitive to GDNF during the first week of injury, suggesting GDNF's potential in promoting dPSN survival and regeneration.

Neurotransmitter-specific therapies

Understanding the neurotransmitter phenotypes of dPSNs can inform the development of more targeted therapies to enhance functional recovery after SCI.

Study Limitations

1
The number of GFP-labeled neurons using the G-rabies method was relatively small, representing only a subpopulation of dPSNs.
2
Some long dendritic branches may have been lost during slice preparation for reconstruction.
3
The mechanism by which the G-rabies virus only labels a small number of neurons is not clear.

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