Int J Oral Biol.  2013 Mar;38(1):5-12.

Effects of NaOCl on Neuronal Excitability and Intracellular Calcium Concentration in Rat Spinal Substantia Gelatinosa Neurons

• Lee HI
• Park AR
• Chun SW

Abstract

Recent studies indicate that reactive oxygen species (ROS) can act as modulators of neuronal activity, and are critically involved in persistent pain primarily through spinal mechanisms. In this study, we investigated the effects of NaOCl, a ROS donor, on neuronal excitability and the intracellular calcium concentration ([Ca2+]i) in spinal substantia gelatinosa (SG) neurons. In current clamp conditions, the application of NaOCl caused a membrane depolarization, which was inhibited by pretreatment with phenyl-N-tert-buthylnitrone (PBN), a ROS scavenger. The NaOCl-induced depolarization was not blocked however by pretreatment with dithiothreitol, a sulfhydryl-reducing agent. Confocal scanning laser microscopy was used to confirm whether NaOCl increases the intracellular ROS level. ROS-induced fluorescence intensity was found to be increased during perfusion of NaOCl after the loading of 2',7'-dichlorofluorescin diacetate (H2DCF-DA). NaOCl-induced depolarization was not blocked by pretreatment with external Ca2+ free solution or by the addition of nifedifine. However, when slices were pretreated with the Ca2+ ATPase inhibitor thapsigargin, NaOCl failed to induce membrane depolarization. In a calcium imaging technique using the Ca2+-sensitive fluorescence dye fura-2, the [Ca2+]i was found to be increased by NaOCl. These results indicate that NaOCl activates the excitability of SG neurons via the modulation of the intracellular calcium concentration, and suggest that ROS induces nociception through a central sensitization.

Keyword

NaOCl; membrane excitability; confocal scanning; calcium imaging

MeSH Terms

Animals
Calcium
Calcium-Transporting ATPases
Central Nervous System Sensitization
Dithiothreitol
Fluoresceins
Fluorescence
Fura-2
Humans
Membranes
Microscopy, Confocal
Neurons
Nociception
Perfusion
Rats
Reactive Oxygen Species
Substantia Gelatinosa
Thapsigargin
Tissue Donors
Calcium
Calcium-Transporting ATPases
Dithiothreitol
Fluoresceins
Fura-2
Reactive Oxygen Species
Thapsigargin