Release Probability-Dependent Scaling of the Postsynaptic Responses at Single Hippocampal GABAergic Synapses

• DOI: 10.1523/jneurosci.3106-06.2006
• Publication Date: 2006-11-29T22:55:24Z
• Authors: Ágota A. Biró; Noémi B. Holderith; Zoltan Nusser
• Keywords: Postsynaptic Current; Active zone

The amount of neurotransmitter released after the arrival an action potential affects strength and trial-to-trial variability postsynaptic responses. Most studies examining dependence synaptic concentration on release probability ( P r ) have focused glutamatergic synapses. Here we asked whether univesicular or multivesicular characterizes transmission at hippocampal GABAergic We used multiple functional analysis to derive quantal parameters inhibitory connections between cannabinoid receptor- cholecystokinin (CCK)-expressing interneurons CA3 pyramidal cells. After recordings, cells were visualized reconstructed light-microscopic level, number boutons mediating IPSCs was determined using electron microscopy (EM). active zones (AZs) per CCK-immunopositive bouton from three-dimensional EM reconstructions, thus allowing calculation total AZs for each pair. Our results reveal approximate fivefold discrepancy numbers functionally sites (17.4 ± 3.2) structurally identified (3.7 0.9). Channel modeling predicts that a sevenfold increase in peak GABA is required enhancement Kinetic unitary indicates most likely attributable release. This change transient together with extremely low receptor occupancy permits -dependent scaling response generated single contact.