Transmissible spongiform encephalopathies (TSEs) are characterized by the accumulation of amyloid fibrils mainly composed of pathological isoforms of the prion protein (PrPTSE). PrPTSE amyloid fibrils are believed to induce the spongiform degeneration and neuron loss typical of TSEs possibly through the alteration of membrane permeability. The effect of PrPTSE on cellular membranes has been modeled in vitro by synthetic peptides that are, however, only partially representative of PrPTSE isoforms found in vivo. In this prospective, a fundamental aspect to clarify is whether the interaction between PrPTSE and the lipid bilayer leads to the formation of pores that allow the passage of discrete ion currents or if the hydrophobic portions of the pathologic protein may alter the correct assembly of the membrane leading to massive perturbations of ionic conductivity. We studied permeability changes of synthetic membranes exposed to PrPTSE extracted from TSE-infected hamster brains and found that PrPTSE induces membrane instability similar to massive invasion and random opening of ionic pathways. The biophysical properties of these putative ionic channels or pores show unusual kinetic characteristics compared to well characterized conventional protein forming ion channels. Furthermore, membrane permeability show asymmetry of current flow according to the side in which PrPTSE and calcium ions were added.