The electroporation can be used as a non-toxic method for introducing exo- genous macromolecules, especially DNA and drugs, into various types of cells. Research into new therapeutic methods based on Long Duration Electroporation (LDE) is of special interest. A new current-clamp method makes possible the electroporation of very long duration with no damage to bio-membranes. In this paper we compare responses of lipid planar bilayer membranes at physiological concentration of KCl, with lipid membranes formed at higher ionic strength, and membranes containing cholesterol. A longer lifespan of the membranes with cholesterol and membranes with increased ionic strength could be observed. Sensitivity of the power spectrum response to the presence of cholesterol, ionic strength, current intensity, and membrane ageing was examined. The membrane memory was analyzed by means of autocorrelation function and rescaled range analysis. We showed that the memory of the system decreases for higher current intensities and this relation is pronounced better at higher ionic strength. At low current intensities all membranes showed slightly persistent type of noise behavior with crossover to Brownian type of noise for higher current value. The transition was much faster for higher ionic strength, where the next transition to anti-persistent response was observed for relatively low currents. Very interesting results were obtained from power spectrum analysis. At low current intensity, all membranes exhibited 1/f \ noise, which disappeared for higher currents, maintaining f^\beta type with rising value of \beta . Membranes formed at lower ionic strength and with cholesterol showed a pronounced tendency to lose flicker noise while ageing, also with rising \beta value.

PACS numbers: 87.16.Dg, 05.45.Tp