biostudies-literatureUnknown110(24)Aldahabi MA stunning example of synaptic diversity is the postsynaptic target cell-type-dependent difference in synaptic efficacy in cortical networks. Here, we show that CA1 pyramidal cell (PC) to fast spiking interneuron (FSIN) connections have 10-fold larger release probability (P_v) than those on oriens lacunosum-moleculare (O-LM) interneurons. Freeze-fracture immunolabeling revealed that different nano-topologies and coupling distances between Ca²⁺ channels and release sites (RSs) are not responsible for the distinct P_v. Although [Ca²⁺] transients are 40% larger in FSINs innervating boutons, when [Ca²⁺] entry is matched in the two bouton populations, EPSCs in O-LM cells are still 7-fold smaller. However, application of a phorbol ester analogNeuron4144-4161.e7https://www.ebi.ac.uk/biostudies/studies/S-EPMC9796815biostudies-literatureDifferent priming states of synaptic vesicles underlie distinct release probabilities at hippocampal excitatory synapses.PMC9796815Holderith NAldahabi MBalint FReva MNusser ZLorincz AfalseDifferent priming states of synaptic vesicles underlie distinct release probabilities at hippocampal excitatory synapses.A stunning example of synaptic diversity is the postsynaptic target cell-type-dependent difference in synaptic efficacy in cortical networks. Here, we show that CA1 pyramidal cell (PC) to fast spiking interneuron (FSIN) connections have 10-fold larger release probability (P_v) than those on oriens lacunosum-moleculare (O-LM) interneurons. Freeze-fracture immunolabeling revealed that different nano-topologies and coupling distances between Ca²⁺ channels and release sites (RSs) are not responsible for the distinct P_v. Although [Ca²⁺] transients are 40% larger in FSINs innervating boutons, when [Ca²⁺] entry is matched in the two bouton populations, EPSCs in O-LM cells are still 7-fold smaller. However, application of a phorbol ester analog2022-01-01T00:00:00Z2022 Dec2025-04-22T18:00:55.175Z2025-04-06T02:20:16.164ZS-EPMC97968153626103310.1016/j.neuron.2022.09.035