Effects of various ion transport inhibitors on the water response in the superior laryngeal nerve in rats

The effects of inhibitors [acetazolamide, an inhibitor of carbonic anhydras e; amiloride, an inhibitor of the Na channel; furosemide, an inhibitor of t he Na/K/2Cl transporter; 4,4 ' -diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), an inhibitor of the Cl channel] on the water response in the super ior laryngeal nerve (SLN) were investigated using whole nerve recordings fr om the SLN of anesthetized and paralyzed rats. Changes in spontaneous activ ity in the SLN after i.v. injection of a hypo- or hypertonic solution were also investigated. The water response to higher concentration amiloride sol utions (0.1, 1, 5 and 10 mM) were significantly smaller in comparison with the control, i.e. the water response to deionized water (88-59% of the cont rol, Fisher's PLSD, P < 0.05). DIDS suppressed the water response significa ntly at concentrations of 0.5 and 2 mM by 18 and 33%, respectively (P < 0.0 5). Likewise, acetazolamide (2 mM) and furosemide (5 mM) significantly supp ressed the water response by 9 and 40%, respectively (P < 0.05). An i.v. bo lus injection of a hypertonic solution (1 ml of 1.5 M NaCl or 1.0 M mannito l) depressed spontaneous activity of the SLN. In contrast, an i.v. injectio n of a hypotonic solution (0.015 M NaCl) increased spontaneous activity The se results suggest that several ion transporters and ion channels, as well as carbonic anhydrase, that may exist in the dorsal surface in the epiglott is may regulate the water response in the SLN and that osmotic changes in t he dorsal surface of the epiglottis and in the interstitial space can affec t nerve activity in the SLN.