Prostaglandin E2 has no effect on two components of tetrodotoxin-resistant Na+ current in mouse dorsal root ganglion.
One possible mechanism underlying inflammation-induced sensitization of the primary afferent neuron is the upregulation of tetrodotoxin-resistant (TTX-R) Na(+) current by inflammatory mediators such as prostaglandins. This notion is based on reports that showed an augmentation of TTX-R Na(+) current following an application of prostaglandin E(2) (PGE(2)) in dorsal root ganglion (DRG) neurons. However, no information was available on the properties of the novel type of TTX-R Na(+) channel, Na(V)1.9, at times when these reports were published. Hence, the contribution of Na(V)1.9 to the PGE(2)-induced upregulation of TTX-R Na(+) current remains to be elucidated. To further examine the modulation of TTX-R Na(+) current by PGE(2), we recorded two components of TTX-R Na(+) current in isolation from small (<25 microm in diameter) DRG neurons using wild-type and Na(V)1.8 knock-out mice. Unexpectedly, neither the component mediated by Na(V)1.8 nor the persistent component mediated by Na(V)1.9 was affected by PGE(2) (1 and 10 microM). Our results raise a question regarding the well-known modulatory role of PGE(2) on TTX-R Na(+) current in inflammatory hyperalgesia.
Zheng
Taixing
T
Department of Neurophysiology, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima 734-8551, Japan.
Kakimura
Jun-ichi
J
Matsutomi
Tomoya
T
Nakamoto
Chizumi
C
Ogata
Nobukuni
N
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D002478:Cells, Cultured; D015232:Dinoprostone / Q000494:pharmacology*; D004351:Drug Resistance; D005727:Ganglia, Spinal / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D062559:NAV1.8 Voltage-Gated Sodium Channel; D009761:Nystatin / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology*
D062559:NAV1.8 Voltage-Gated Sodium Channel; C568318:Scn10a protein, mouse; D015222:Sodium Channels; D009761:Nystatin; D013779:Tetrodotoxin; D012964:Sodium; D015232:Dinoprostone; D002211:Capsaicin