A subpopulation of capsaicin-sensitive porcine dorsal root ganglion neurons is lacking hyperpolarization-activated cyclic nucleotide-gated channels.
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels contribute to stabilizing resting membrane potential, thus controlling neuron excitability. Subclasses of nociceptive neurons differ in their excitability, therefore, these channels could be a distinguishing marker. We investigated isolated dorsal root ganglion neurons from a non-rodent species, the pig, Sus scrofa domesticus. Single labeling revealed capsaicin-induced cobalt-uptake in 54.3% and transient receptor potential V1 (TRPV1) immunoreactivity in 55.1% of all neurons. Ruthenium red and capsazepine suppressed capsaicin-induced cobalt-uptake. HCN-1 and HCN-2 channel isoform immunoreactivity was detected in 82.6% and 88.3%, respectively, and binding of IB4 in 29.4% of all neurons. Double labeling revealed that out of the capsaicin-positive neurons, 42.3% were IB4-positive, 80.0% immunoreactive for the HCN-1, and 77.3% for the HCN-2 channel isoform, respectively. Neurons lacking HCN-1 or HCN-2 channel isoforms were mostly capsaicin-positive and IB4-negative. The soma size of neurons lacking HCN-1 and/or HCN-2 channels was small to medium. Western blot analysis showed protein products of sizes similar to those of HCN-1 and HCN-2 channel isoforms. Functionally, in patch-clamp experiments, some neurons were unresponsive to membrane hyperpolarization, thus, probably lacking HCN channels. In conclusion, in porcine dorsal root ganglion neurons there is a subset of capsaicin-positive, IB4-negative neurons lacking HCN-1 and/or HCN-2 channel isoforms.
Obreja
Otilia
O
Department of Anesthesiology and Intensive Care Medicine, Faculty of Clinical Medicine, University of Heidelberg, Mannheim, Germany.
Klusch
Andreas
A
Ponelies
Norbert
N
Schmelz
Martin
M
Petersen
Marlen
M
D000818:Animals; D015153:Blotting, Western; D002211:Capsaicin / Q000494:pharmacology; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000502:physiology*; D005260:Female; D005455:Fluorescent Antibody Technique; D005727:Ganglia, Spinal / Q000166:cytology* / Q000502:physiology*; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000145:classification / Q000187:drug effects / Q000502:physiology*; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D037121:Plant Lectins; D015221:Potassium Channels / Q000502:physiology*; D018689:Sensory System Agents / Q000494:pharmacology; D034421:Sus scrofa; D050916:TRPV Cation Channels / Q000037:antagonists & inhibitors / Q000502:physiology
D054815:Cyclic Nucleotide-Gated Cation Channels; C045475:Griffonia simplicifolia lectins; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D037121:Plant Lectins; D015221:Potassium Channels; D018689:Sensory System Agents; D050916:TRPV Cation Channels; D002211:Capsaicin