title: Co-expression of the voltage-gated potassium channel Kv1.4 with transient receptor potential channels (TRPV1 and TRPV2) and the cannabinoid receptor CB1 in rat dorsal root ganglion neurons.
abstract: Potassium channels contribute to basic neuronal excitability and modulation. Here, we examined expression patterns of the voltage-gated potassium channel Kv1.4, the nociceptive transduction channels TRPV1 and TRPV2 as well as the putative anti-nociceptive cannabinoid receptor CB1 by immunofluorescence double-labelings in sections of rat dorsal root ganglia (DRGs). Kv1.4, TRPV1 and CB1 were each detected in about one third of neurons (35.7+/-0.5%, 29.4+/-1.1% and 36.4+/-0.5%, respectively, mean diameter 19.1+/-0.3 microm). TRPV2 was present in 4.4+/-0.4% of all neurons that were significantly larger in diameter (27.4+/-0.7 microm; P < 0.001). Antibody double-labeling revealed that the majority of Kv1.4-positive neurons co-expressed TRPV1 (73.9+/-1.5%) whereas none expressed TRPV2. The largest overlap was found with CB1 (93.1+/-0.1%). CB1 expression resembled that seen for Kv1.4 since the majority of neurons expressing CB1-protein also expressed TRPV1 (69.4+/-6.5%) but not TRPV2 (0.6+/-0.3%). When CB1-mRNA was detected using in situ hybridizations an additional subset of larger neurons was labeled including 82.4+/-17.7% of the TRPV2 expressing neurons. However, co-localization of Kv1.4 with CB1-mRNA (92%, mean diameter: 18.5 microm) was essentially the same as with CB1-protein. The almost complete overlap of CB1 and Kv1.4 in nociceptive DRG neurons suggests a functional synergistic action between Kv1.4 and CB1. The potassium channel may have two important roles in nociception. As the molecular basis of A-type current it could be involved in the control of repetitive discharges at peripheral terminals and as a downstream signal transduction site of CB1 in the control of presynaptic transmitter release at central terminals.
authors.affiliation: Institute of Physiology and Pathophysiology, Johannes Gutenberg-University, Saarstrasse 21, D-55099, Mainz, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Binzen
authors.forename: W
authors.initials: W
authors.lastname: Greffrath
authors.forename: S
authors.initials: S
authors.lastname: Hennessy
authors.forename: M
authors.initials: M
authors.lastname: Bausen
authors.forename: S
authors.initials: S
authors.lastname: Saaler-Reinhardt
authors.forename: R-D
authors.initials: RD
authors.lastname: Treede
mesh_terms: D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002452:Cell Count / Q000379:methods; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000166:cytology*; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D009474:Neurons / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D051672:Shal Potassium Channels / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000378:metabolism*
chemical_list: D043884:Receptor, Cannabinoid, CB1; D051672:Shal Potassium Channels; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; C476722:Trpv2 protein, rat