NaN/Nav1.9: a sodium channel with unique properties

Area of Science:

• Neuroscience
• Molecular Biology
• Pain Research

Background:

• The Nav1.9 sodium channel (NaN) is primarily found in nociceptive neurons within the dorsal root ganglia (DRG) and trigeminal ganglia.
• Nav1.9 generates a persistent, tetrodotoxin-resistant sodium current, characterized by significant overlap between activation and inactivation curves.
• This channel influences the resting membrane potential and amplifies minor depolarizations in primary nociceptive neurons.

Purpose of the Study:

• To investigate the role of Nav1.9 in the electrophysiological properties of primary nociceptive neurons.
• To explore the potential contribution of Nav1.9 downregulation to neuronal hyperexcitability following nerve injury.
• To evaluate Nav1.9 as a potential therapeutic target for pain management.

Main Methods:

• Electrophysiological recordings to characterize Nav1.9 currents.
• Analysis of Nav1.9 expression levels in DRG neurons.
• Investigation of the effects of glial cell-derived neurotrophic factor (GDNF) on Nav1.9 expression and neuronal excitability.

Main Results:

• Nav1.9 exhibits unique properties, including a persistent current and modulation of neuronal resting potential.
• Downregulation of Nav1.9 was observed following peripheral axotomy, linked to reduced GDNF levels.
• This downregulation may contribute to the hyperexcitability of DRG neurons post-nerve injury.

Conclusions:

• Nav1.9 plays a significant role in the excitability of nociceptive neurons and pain signaling.
• Altered Nav1.9 function, particularly its downregulation, is implicated in neuropathic pain mechanisms.
• Targeting Nav1.9 presents a promising strategy for developing novel pain therapies.