[Interaction of isolated brain synaptic vesicles with flat bilayer membranes in the rat]

The conductivity of planar bilayer membrane comprising asolectin and phosphatidylserine (concentration ratio 9:1) in a buffer solution increased sharply in the presence of synaptic vesicles (SV) isolated from the rat brain and added to one side of the membrane only. The bilayer remained stable upon modification, and the conductivity increment was dependent on SV concentration in the range from 4 to 16 mu of the total protein per ml. If I mM CaCl2 was present in the buffer solution, the conductivity increased by 2 to 3 orders of magnitude upon the addition of SV at a final concentration of 3-4 mu protein per ml. The membrane was unstable and its rupture occurred often at an early stage of conductivity changes. In the absence of SV addition the membrane was stable, with its conductivity remaining unchanged for 2 h and more. With I mM CaCl2 addition to the solution already containing SV, no conductivity changes were observed, the cause perhaps, being Ca2+-induced SV aggregation.