Kolesnyk O. Regulation of short-term plasticity GABAergic synaptic transmission between hippocampalneurons

In the present study, we investigated calcium- and frequency-dependent mechanisms of regulation of short-term plasticity of GABAergic transmission in cultured hippocampal neurons.Changes in amplitudes of evoked inhibitory postsynaptic currents from rat cultured hippocampal neurons were studied using whole-cell patch-clamp technique in postsynaptic neuron and local extracellular electrical paired pulse stimulation of single presynaptic axon. According to coefficient of variance analysis (CV) was found that CV of second respond was significantly larger than CV first during depression and significantly smaller during facilitation. Thus, only presynaptic mechanism underlies short-term depression and facilitation. We also estimated quantal parameters assuming that transmitter release is reasonably described by a binomial distribution. There is significant difference in quantal parameters characterizing GABA release during increasing and decreasing of efficacy of synaptic transmission. The frequency range of regulation of short-term properties of depression and facilitation at the GABAergic synapse of the hippocampus is described in detail. Rate recovery from paired pulse depression is well described by a single exponential function and recovery from paired pulse facilitation has bell-shape form. It is shown that calcium-dependent changes in the efficacy of synaptic transmission are modulated only by P/Q and N-types of high-threshold calcium channels, and calcium ATPase of the endoplasmic reticulum has no effect on this process.