Plasticity in the spinal cord: the dorsal root connection

Area of Science:

• Neuroscience
• Spinal Cord Injury Research
• Neural Plasticity

Background:

• Partial denervation of spinal cord targets triggers a natural increase in projections from intact neuronal systems.
• This phenomenon, known as sprouting, is comparable to denervation-evoked sprouting observed elsewhere in the central nervous system (CNS).
• Sprouting is a regulated process, not random, with specific neuronal systems responding to denervated areas.

Purpose of the Study:

• To investigate the phenomenon of naturally occurring sprouting in the spinal cord.
• To understand the factors regulating sprouting, including age and additional manipulations.
• To explore the implications of neural plasticity for recovery of function after CNS lesions.

Main Methods:

• Analysis of projection density changes in intact neuronal systems following partial denervation of spinal cord targets.
• Quantitative methods to demonstrate increased projections, particularly in adult models.
• Investigating the effects of peripheral nerve injury and other manipulations on enhancing sprouting in adults.
• Comparing sprouting patterns in neonates versus adults.

Main Results:

• Sprouting in adults is typically limited to normal target zones, requiring rigorous methods for detection.
• Greater plasticity, including regenerative changes, can be induced in dorsal root ganglion (DRG) cells by peripheral nerve lesions.
• Sprouting into novel territories in adults is more pronounced when combined with peripheral nerve injury, suggesting metabolic drive can override limitations.
• Neonates exhibit fewer limitations, with extensive sprouting into aberrant targets if denervation occurs before developmental cessation.
• Altered synaptic activity patterns can induce long-lasting modifications in neuronal synthetic activity and spinal neuron function.

Conclusions:

• Naturally occurring neural plasticity, including sprouting, is a significant compensatory mechanism following CNS lesions.
• Understanding this plasticity is crucial for evaluating the consequences of CNS injuries.
• This innate capacity for change influences the extent of functional recovery and offers potential avenues for therapeutic enhancement.