Pharmacological modification of ionic currents elicited in epithelia by sensory neuropeptides

A stimulation of afferent neuronal endings in such epithelial organs as airways, colon and frog skin produces reversible hyperpolarization, usually explained as caused by neuropeptides released from sensory endings. The aim of this study was to examine pharmacological modifications of these electrophysiological reactions, which were evoked by the inhibition of Na+ or Cl- transepithelial transport by application of amiloride (AMI) and bumetanide (BUME). The tissues were mounted in a modified Ussing chamber which was additionally equipped with a nozzle connected to a peristaltic pump and acting as a stimulation device. In the resting, control conditions the transepithelial potential differences--PD of tracheal and colonic walls and frog skin were: -3.3 +/- 0.4, -3.0 +/- 0.4 and -16.5 +/- 4.1 mV, respectively and hyperpolarization after mechanical stimulation--dDP for the same organs was: -1.2 +/- 0.3, -1.2 +/- 0.3 and -2.4 +/- 0.4, respectively. Preincubation with AMI influenced the dPD in all tissues but the PD of the frog skin was only depolarized. Preincubation of the tissues with BUME diminished dPD in all organs. A hypothesis was put forward that epithelial hyperpolarization of tracheal and colonic walls depends on the combined augmentation of Na+ and Cl- transport processes, whereas epithelial hyperpolarization of frog skin depends entirely on Na+ currents and all these transepithelial ionic currents have an adapting value.