Published in:
Open Access
01-12-2022 | Migraine | Research
Contribution of tetrodotoxin-resistant persistent Na+ currents to the excitability of C-type dural afferent neurons in rats
Authors:
Michiko Nakamura, Il-Sung Jang
Published in:
The Journal of Headache and Pain
|
Issue 1/2022
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Abstract
Background
Growing evidence supports the important role of persistent sodium currents (INaP) in the neuronal excitability of various central neurons. However, the role of tetrodotoxin-resistant (TTX-R) Na+ channel-mediated INaP in the neuronal excitability of nociceptive neurons remains poorly understood.
Methods
We investigated the functional role of TTX-R INaP in the excitability of C-type nociceptive dural afferent neurons, which was identified using a fluorescent dye, 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchloride (DiI), and a whole-cell patch-clamp technique.
Results
TTX-R INaP were found in most DiI-positive neurons, but their density was proportional to neuronal size. Although the voltage dependence of TTX-R Na+ channels did not differ among DiI-positive neurons, the extent of the onset of slow inactivation, recovery from inactivation, and use-dependent inhibition of these channels was highly correlated with neuronal size and, to a great extent, the density of TTX-R INaP. In the presence of TTX, treatment with a specific INaP inhibitor, riluzole, substantially decreased the number of action potentials generated by depolarizing current injection, suggesting that TTX-R INaP are related to the excitability of dural afferent neurons. In animals treated chronically with inflammatory mediators, the density of TTX-R INaP was significantly increased, and it was difficult to inactivate TTX-R Na+ channels.
Conclusions
TTX-R INaP apparently contributes to the differential properties of TTX-R Na+ channels and neuronal excitability. Consequently, the selective modulation of TTX-R INaP could be, at least in part, a new approach for the treatment of migraine headaches.