title: Epithelial modulation of afferent nerve endings: differential effects of amiloride on afferent subtypes.
abstract: Mechanisms underlying the differing chemosensitivity of laryngeal afferents have not been defined. The role of airway epithelium in transducing the chemical stimuli to neural signals was investigated by using Na(+)- and Cl(-)-channel inhibitors in anesthetized spontaneously breathing cats. Single-fiber action potentials were recorded from the peripheral cut end of the superior laryngeal nerve. Luminal application of amiloride (10(-4) M), an inhibitor of epithelial Na+ channels, reduced the responsiveness of non-respiratory-modulated endings (n = 25) to distilled water (65.76 +/- 5.77 vs. 50.67 +/- 5.13 Hz; P < 0.01). Water responsiveness of these endings was unaffected by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and diphenylamine-2-carboxylate, two Cl(-)-channel blockers. Respiratory-modulated endings (water responsive, n = 8; water nonresponsive, n = 9) were unaffected by Na(+)- and Cl(-)-channel blockers. These results suggest that epithelial Na+ channels play a role in the modulation of non-respiratory-modulated laryngeal endings. The lack of an effect by amiloride on other subtypes may be due to differences in location or intrinsic properties of nerve endings. Cl- channels do not appear to play an important role in the modulation of laryngeal afferents targeted in this study.
authors.affiliation: Department of Pediatrics, East Carolina University School of Medicine, Greenville, North Carolina 27858, USA.
authors.forename: T K
authors.initials: TK
authors.lastname: Ghosh
authors.forename: M R
authors.initials: MR
authors.lastname: Van Scott
authors.forename: O P
authors.initials: OP
authors.lastname: Mathew
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000344:Afferent Pathways / Q000187:drug effects* / Q000502:physiology; D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002415:Cats; D004848:Epithelium; D017136:Ion Transport; D007823:Laryngeal Nerves / Q000187:drug effects*; D009411:Nerve Endings; D009994:Osmolar Concentration; D013997:Time Factors
chemical_list: D000584:Amiloride; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid