Expression of hyperpolarization-activated cyclic nucleotide-gated cation channels in rat dorsal root ganglion neurons innervating urinary bladder

• Published in: Brain research 2006-11, Vol.1119 (1), p.115-123
• Main Authors: Matsuyoshi, Hiroko, Masuda, Noriyuki, Chancellor, Michael B., Erickson, Vickie L., Hirao, Yoshihiko, de Groat, William C., Wanaka, Akio, Yoshimura, Naoki
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Cell Size; Cyclic Nucleotide-Gated Cation Channels; Dorsal root ganglion; Female; Fluorescent Dyes; Fundamental and applied biological sciences. Psychology; Ganglia, Spinal - cytology; Ganglia, Spinal - metabolism; Hyperpolarization-activated cyclic nucleotide-gated cation channel; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; Immunohistochemistry; Ion Channels - metabolism; Nerve Fibers, Myelinated - metabolism; Nerve Fibers, Myelinated - ultrastructure; Nerve Fibers, Unmyelinated - metabolism; Nerve Fibers, Unmyelinated - ultrastructure; Neurons, Afferent - cytology; Neurons, Afferent - metabolism; Posterior Horn Cells - cytology; Posterior Horn Cells - metabolism; Potassium Channels - metabolism; Rats; Rats, Sprague-Dawley; Reflex - physiology; Spinal cord; Urinary bladder; Urinary Bladder - innervation; Urinary Bladder - physiology; Urination - physiology; Vertebrates: urinary system; Visceral Afferents - cytology; Visceral Afferents - metabolism
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2006.08.052

Afferent pathways innervating the urinary bladder consist of myelinated Aδ- and unmyelinated C-fibers, the neuronal cell bodies of which correspond to medium and small-sized cell populations of dorsal root ganglion (DRG) neurons, respectively. Since hyperpolarization-activated cyclic nucleotide-gated cation (HCN) channel currents have been identified in various peripheral sensory neurons, we examined the expression of isoforms of HCN channels in the L6-S1 spinal cord and bladder afferent neurons from L6-S1 DRG in rats. Among HCN-1, HCN-2 and HCN-4 channel subtypes, positive staining with HCN-2 antibodies was found in the superficial dorsal horn of the spinal cord and small- and medium-sized unidentified DRG neurons. In dye-labeled bladder afferent neurons, HCN-2-positive cells were found in approximately 60% of neurons, and HCN-2 was expressed in both small- and medium-sized neurons with a higher ratio (expression ratio: 61% and 50% of neurons, respectively) compared with unidentified DRG neurons, in which the HCN expression ratio was 47% and 21% of small- and medium-sized cells, respectively. These results suggest that HCN-2 is the predominant subtype of HCN channels, which can control neuronal excitability, in small-sized C-fiber and medium-sized Aδ fiber DRG neurons including bladder afferent neurons, and might modulate activity of bladder afferent pathways controlling the micturition reflex.