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Loose-patch recordings of single quanta at individual hippocampal synapses

Nature volume 388, pages 874–878 (1997)Cite this article

Abstract

Synapses in the central nervous system are typically studied by recording electrical responses from the cell body of the postsynaptic cell. Because neurons are normally connected by multiple synaptic contacts, these postsynaptic responses reflect the combined activity of many thousands synapses, and it remains unclear to what extent the properties of individual synapses can be deduced from the population response1,2,3,4,5. We have therefore developed a method for recording the activity of individual hippocampal synapses. By capturing an isolated presynaptic bouton inside a loose-patch pipette and recording from the associated patch of postsynaptic membrane, we were able to detect miniature excitatory postsynaptic currents (‘minis’) arising from spontaneous vesicle exocytosis at a single synaptic site, and to compare these with minis recorded simultaneously from the cell body. The average peak conductance at a single synapse was about 900 pS, corresponding roughly to the opening of 90 AMPA-type glutamate-receptor channels. The variability in this conductance was about 30%, matching the value reported for the neuromuscular junction6. Given that our synapses displayed single postsynaptic densities (PSDs), this variability is larger than would be predicted from the random opening of receptor channels, suggesting that they are not saturated by the content of a single vesicle. Therefore the response to a quantum of neurotransmitter at these synapses is not limited by the number of available postsynaptic receptors.

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Figure 1: Loose-patch synaptic recordings.
Figure 2: Miniature currents from single CA3-CA1 hippocampal synapses.
Figure 3: Simultaneous synaptic and somatic-wc recordings.
Figure 4: Quantal variability at single hippocampal synapses.

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Acknowledgements

We thank D. DiFrancesco, D. S. Faber, A. Marty, J. Meldolesi and R. W. Tsien for comments on the manuscript, and A. Abenavoli, L. Anghinoni, M. Caimi, P. Cerutti, E. Naldi and J. Noel for help and discussion. L.F. was the recipient of a postdoctoral fellowship from the University of Milano. This research was supported by grants from EC Biomed-2, Telethon and PNR/Neurobiology (MURST-Italy) to A.M.

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  1. Department of Biological and Technological Research, Department of Pharmacology, DIBIT, Scientific Institute San Raffaele, and Cellular and Molecular Pharmacology Center, CNR, University of Milano, Via Olgettina 58, 20123, Milano, Italy

    Lia Forti, Mario Bossi, Andrea Bergamaschi, Antonello Villa & Antonio Malgaroli

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  1. Lia Forti
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Correspondence to Antonio Malgaroli.

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Forti, L., Bossi, M., Bergamaschi, A. et al. Loose-patch recordings of single quanta at individual hippocampal synapses. Nature 388, 874–878 (1997). https://doi.org/10.1038/42251

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