Presynaptic control of efficacy of GABAergic synapses in the hippocampus

First we found that applying substances that change intracellular presynapt ic GABA concentration alter the synaptic efficacy of hippocampal GABAergic neurons. The amplitude as well as the frequency of occurrence of spontaneou s postsynaptic currents (mIPSCs) are affected. Then, we developed a model o f presynaptic vesicle dynamics to better understand the causal relationship between cytosolic GABA concentration and mIPSC amplitude and frequency. On e way to explain our experimental findings is to postulate that the filling of vesicles as well as their transition into the readily releasable pool d epends on vesicular GABA content. (C) 2001 Elsevier Science B.V. Ah rights reserved.