Characterization of ion currents elicited by a stream of fluid during spontaneous and ligand-induced chloride current oscillation in Xenopus laevis oocytes.

During Ca2+-activated C- current oscillations a mechanical deformation of the Xenopus laevis oocyte by a fluid stream evokes transient inward currents of high amplitude (stream evoked inward current, Ii,st). This current can be observed either in native or RNA-injected oocytes expressing ligand-controlled ion channels from rat brain. Ii,st reversed at the equilibrium potential of chloride and was blocked by 9-anthracene carboxylic acid (2 mM). Power spectral analysis of the oscillations did not reveal a correlation between the features of the oscillations and the amplitude of Ii,st. Antagonists of stretch-activated cation channels [gadolinium (100 microM) and lanthanum (1mM)] did not block Ii,st. Calcium channel blockers [cobalt and manganese (10 mM)] did not inhibited Ii,st and Ii,st could also be elicited in calcium-free medium. Preloading oocytes with pertussis toxin (PTX) for 17 h prevented current oscillations and Ii,st caffeine (10 mM), an antagonist of the liberation of calcium from intracellular stores, inhibited Ii,st. Our results proride evidence for modulation of the mechanosensitivity of chloride currents by activation of intracellular second messenger cascades.