title: Trigeminal ganglion neurons of mice show intracellular chloride accumulation and chloride-dependent amplification of capsaicin-induced responses.
abstract: Intracellular Cl(-) concentrations ([Cl(-)](i)) of sensory neurons regulate signal transmission and signal amplification. In dorsal root ganglion (DRG) and olfactory sensory neurons (OSNs), Cl(-) is accumulated by the Na(+)-K(+)-2Cl(-) cotransporter 1 (NKCC1), resulting in a [Cl(-)](i) above electrochemical equilibrium and a depolarizing Cl(-) efflux upon Cl(-) channel opening. Here, we investigate the [Cl(-)](i) and function of Cl(-) in primary sensory neurons of trigeminal ganglia (TG) of wild type (WT) and NKCC1(-/-) mice using pharmacological and imaging approaches, patch-clamping, as well as behavioral testing. The [Cl(-)](i) of WT TG neurons indicated active NKCC1-dependent Cl(-) accumulation. Gamma-aminobutyric acid (GABA)(A) receptor activation induced a reduction of [Cl(-)](i) as well as Ca(2+) transients in a corresponding fraction of TG neurons. Ca(2+) transients were sensitive to inhibition of NKCC1 and voltage-gated Ca(2+) channels (VGCCs). Ca(2+) responses induced by capsaicin, a prototypical stimulus of transient receptor potential vanilloid subfamily member-1 (TRPV1) were diminished in NKCC1(-/-) TG neurons, but elevated under conditions of a lowered [Cl(-)](o) suggesting a Cl(-)-dependent amplification of capsaicin-induced responses. Using next generation sequencing (NGS), we found expression of different Ca(2+)-activated Cl(-) channels (CaCCs) in TGs of mice. Pharmacological inhibition of CaCCs reduced the amplitude of capsaicin-induced responses of TG neurons in Ca(2+) imaging and electrophysiological recordings. In a behavioral paradigm, NKCC1(-/-) mice showed less avoidance of the aversive stimulus capsaicin. In summary, our results strongly argue for a Ca(2+)-activated Cl(-)-dependent signal amplification mechanism in TG neurons that requires intracellular Cl(-) accumulation by NKCC1 and the activation of CaCCs.
authors.affiliation: Department of Cell Physiology, Ruhr-University Bochum, Bochum, Germany. nicole.schoebel@gmx.de
authors.forename: Nicole
authors.initials: N
authors.lastname: Schöbel
authors.forename: Debbie
authors.initials: D
authors.lastname: Radtke
authors.forename: Matthias
authors.initials: M
authors.lastname: Lübbert
authors.forename: Günter
authors.initials: G
authors.lastname: Gisselmann
authors.forename: Ramona
authors.initials: R
authors.lastname: Lehmann
authors.forename: Annika
authors.initials: A
authors.lastname: Cichy
authors.forename: Benjamin S P
authors.initials: BS
authors.lastname: Schreiner
authors.forename: Janine
authors.initials: J
authors.lastname: Altmüller
authors.forename: Alan C
authors.initials: AC
authors.lastname: Spector
authors.forename: Jennifer
authors.initials: J
authors.lastname: Spehr
authors.forename: Hanns
authors.initials: H
authors.lastname: Hatt
authors.forename: Christian H
authors.initials: CH
authors.lastname: Wetzel
mesh_terms: D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling; D002211:Capsaicin / Q000494:pharmacology*; D002478:Cells, Cultured; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism* / Q000502:physiology; D005260:Female; D058787:GABA-A Receptor Antagonists / Q000494:pharmacology; D015870:Gene Expression; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D061251:Primary Cell Culture; D011724:Pyridazines / Q000494:pharmacology; D011963:Receptors, GABA-A / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism; D064506:Solute Carrier Family 12, Member 2; D009435:Synaptic Transmission; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome; D012668:Trigeminal Ganglion / Q000166:cytology* / Q000187:drug effects
chemical_list: D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D018118:Chloride Channels; D002712:Chlorides; D058787:GABA-A Receptor Antagonists; D011724:Pyridazines; D011963:Receptors, GABA-A; C578877:SLC12A2 protein, human; C578878:Slc12a2 protein, mouse; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; C049853:gabazine; D002211:Capsaicin