Calcium ions in the presence of exogenous phosphatidylserine interfere with GABA diffusion through the Deiters' neuron membrane.

Diffusion of GABA through the plasma membrane of GABA-acceptive neurons might be a mechanism of importance for the termination of its synaptic action. In the present investigation we studied the effects of phosphatidylserine (PS) (10(-4)-10(-3) M), Ca2+ 2 mM and PS + 2 mM Ca2+ on such a process. The method involved the use of single microdissected Deiters' membranes which were put between two small microchambers in order to study the passage of GABA across the membrane. The results show that whereas PS and Ca2+ by themselves have no effect on such a process, PS + 2 mM CaCl2 give a significant, although slight, inhibition. The hypothesis that Calcium ion + PS effect is due to a disturbance of the interaction between GABA and endogenous PS molecules of the membrane is discussed.