Publication de 4 numéros par an
ISSN Imprimer: 2155-014X
ISSN En ligne: 2155-0158
Analysis of Quantal Characteristics of GABA Release during Short-Term Depression and Facilitation of Synaptic Transmission
RÉSUMÉ
Changes in amplitudes of evoked paired inhibitory postsynaptic currents (eIPSCs) from rat cultured hippocampal neurons were studied using whole-cell patch-clamp technique and local extracellular electrical paired pulse stimulation of a single presynaptic axon. Paired pulse depression (PPD) and paired pulse facilitation (PPF) were observed in 43 tested neurons. According to the analysis of the coefficient of variation (CV) of eIPSCs, the CV of the second response during depression was significantly larger than that of the first one by 57% (n = 26), while it was smaller by 27% (n = 17) during facilitation. Thus, just presynaptic mechanisms underly short-term depression and facilitation. We also estimated quantal parameters assuming that a transmitter release is reasonably described by a binomial distribution. We have found that under our experimental conditions there were no significant changes in GABA release probability during PPD and PPF. The values of mean quantal content and mean number of sites of transmitter release were the same for the first stimulus in pair, and they were equal 9.7 in depression and 5 in facilitation of synaptic transmission. The values for the second stimulus decreased by 28 and 26% during PPD compared to the initial values, and they increased by 14 and 11%, respectively during PPF. Thus, there is significant difference in quantal parameters characterizing GABA release during short-term depression and facilitation of synaptic transmission.