Targeted intracellular voltage recordings from dendritic spines using quantum-dot-coated nanopipettes

Abstract

Dendritic spines are the primary site of excitatory synaptic input onto neurons, and are biochemically isolated from the parent dendritic shaft by their thin neck. However, due to the lack of direct electrical recordings from spines, the influence that the neck resistance has on synaptic transmission, and the extent to which spines compartmentalize voltage, specifically excitatory postsynaptic potentials, albeit critical, remains controversial. Here, we use quantum-dot-coated nanopipette electrodes (tip diameters ~15–30 nm) to establish the first intracellular recordings from targeted spine heads under two-photon visualization. Using simultaneous somato-spine electrical recordings, we find that back propagating action potentials fully invade spines, that excitatory postsynaptic potentials are large in the spine head (mean 26 mV) but are strongly attenuated at the soma (0.5–1 mV) and that the estimated neck resistance (mean 420 MΩ) is large enough to generate significant voltage compartmentalization. Nanopipettes can thus be used to electrically probe biological nanostructures.

Attenuation of Synaptic Potentials in Dendritic Spines

“…Because of this, our calculations of the neck resistance should be viewed with caution as an underestimate of the real values in vivo. In fact, in a recent work, we used intracellular recordings with glass nanopipettes from spines in brain slices, with longer and narrower neck than in the current voltage imaging study (twice longer neck length on average), and reported neck resistances of 250–536 MΩ (425±102 MΩ), (Jayant et al, 2016). This nanopipette study specifically focused on long necked spines for proper targeting of spine heads.…”

“…Part of the reason is a technical one, because conventional electrophysiology methods are too invasive. Although nanopipettes have been recently used to record intracellularly from dendritic spines (Jayant et al, 2016), non-invasive optical approaches, such as fluorescent recovery after photobleaching and calcium imaging paired with glutamate uncaging, have been used as alternative methods to study the electrical properties of spines. Unfortunately, there are discrepancies in the conclusions of different studies.…”

A roadmap to integrate astrocytes into Systems Neuroscience

“…The emerging combination of two‐photon calcium imaging with SBFSEM for examining neural circuits at cellular resolution may pave the way for subcellular analyses (Vishwanathan et al, ). Finally, recent multiplex Ca 2+ imaging at a single synapse‐astrocyte interface (J. P. Reynolds et al, ), application of nanotechnology to voltage recording in neurons (Jayant et al, ), and FRET‐based analysis of contacts between synapses and astrocytes (Octeau et al, ), are advances toward integrating structure and function in astrocyte mini‐circuits.…”

“…imaging at a single synapse-astrocyte interface (J. P. Reynolds et al, 2019), application of nanotechnology to voltage recording in neurons (Jayant et al, 2017), and FRET-based analysis of contacts between synapses and astrocytes (Octeau et al, 2018), are advances toward integrating structure and function in astrocyte mini-circuits.…”

Counting and Sizing of Single Vesicles/Liposomes by Electrochemical Events

“…As shown in Figure 5B, when r ps is slightly larger or much larger than r 0 (defined as r ps > r 0 and r ps @ r 0 ), the staircase current decrease for capture and hold (a) or the symmetric current blip for collision and departure (b) is observed under the same applied potential. [97,98] within contrast to microelectrode impact events, nanopipette collision events occur without an electrochemical redox probe at the outside sensing zone of the Figure 5. Therefore, size resolution can be achieved according to the different outputs of current events.…”