title: Endothelin-1 (ET-1) selectively enhances the activation gating of slowly inactivating tetrodotoxin-resistant sodium currents in rat sensory neurons: a mechanism for the pain-inducing actions of ET-1.
abstract: Endothelin-1 (ET-1) causes pain through activation of nociceptors, by either direct depolarization or increased excitability. Here we examined the effect of ET-1 on nociceptor-associated tetrodotoxin-resistant (TTX-R) sodium currents using whole-cell voltage clamp of acutely dissociated rat dorsal root ganglion (DRG) neurons. DRG neurons that responded had enhanced activation gating when exposed to 10 nm ET-1, as determined by significant shifts in their average activation midpoint potentials (DeltaE(0.5) = -8.0 +/- 0.5 mV) when compared with control (DeltaE(0.5) = -2.2 +/- 0.4 mV; n = 6) and ET-1 unresponsive cells (DeltaE(0.5) = -3.2 +/- 0.2 mV). ET-1 also modified the availability of TTX-R channels, as determined by negative shifts in the average midpoint potential for inactivation of ET-1 responsive cells when compared with controls. These actions of ET-1 occurred predominantly in cells with more slowly inactivating TTX-R currents. Both time-to-peak current and inactivation time constants were shortened by ET-1 in responsive cells. Previous exposure of cells to the endothelin-A (ET(A)) receptor antagonist BQ-123 (1 microm) prevented ET-1-induced shifts in TTX-R activation. In contrast to changes in TTX-R, ET-1 did not modify tetrodotoxin-sensitive currents recorded from DRG neurons. These results demonstrate that the algogenic peptide ET-1 induces ET(A) receptor-mediated, hyperpolarizing shifts in the voltage-dependent activation of TTX-R Na+ channels, a potential mechanism for selective excitation by ET-1 of nociceptors that we observed in vivo.
authors.affiliation: Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: Zhongren
authors.initials: Z
authors.lastname: Zhou
authors.forename: Gudarz
authors.initials: G
authors.lastname: Davar
authors.forename: Gary
authors.initials: G
authors.lastname: Strichartz
mesh_terms: D000818:Animals; D002469:Cell Separation; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000494:pharmacology*; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism; D015640:Ion Channel Gating / Q000187:drug effects* / Q000502:physiology; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism*; D009619:Nociceptors / Q000187:drug effects / Q000378:metabolism*; D010146:Pain / Q000139:chemically induced / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D019332:Endothelin-1; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; D015222:Sodium Channels; D013779:Tetrodotoxin; D012964:Sodium