Plasticity in Preganglionic and Postganglionic Neurons of the Sympathetic Nervous System during Embryonic Development

Area of Science:

• Neuroscience
• Autonomic Nervous System Physiology
• Cellular Plasticity

Background:

• Sympathetic preganglionic neurons (SPNs) are critical for autonomic nervous system function, integrating central inputs to control peripheral postganglionic neurons (PGNs).
• Understanding the mechanisms regulating SPN and PGN excitability and sympathetic tone is limited.
• SPNs share developmental origins with somatic motor neurons, which exhibit homeostatic plasticity (HP).

Purpose of the Study:

• To investigate whether SPNs exhibit homeostatic plasticity similar to somatic motor neurons.
• To determine if homeostatic mechanisms are present in PGNs, the synaptic targets of SPNs.

Main Methods:

• Utilized an embryonic chick model with reduced excitatory synaptic input to SPNs and PGNs.
• Assessed changes in intracellular chloride levels in SPNs following synaptic blockade.
• Evaluated PGN excitability after both in vivo and ex vivo synaptic input reduction.

Main Results:

• SPNs demonstrated a significant increase in intracellular chloride levels after 2 days of reduced excitatory synaptic input, indicative of GABAergic synaptic scaling.
• This homeostatic plasticity in SPNs suggests a role in establishing baseline excitability.
• Neither in vivo nor ex vivo synaptic input reduction to PGNs induced homeostatic adjustments in their excitability.

Conclusions:

• SPNs possess homeostatic plasticity mechanisms, specifically GABAergic synaptic scaling, which may regulate sympathetic tone early in development.
• PGNs lack similar homeostatic adjustment capabilities, highlighting differences between central and peripheral sympathetic nervous system components.
• These findings contribute to understanding the differential regulation of excitability within the sympathetic nervous system.