Direct electrical access to presynaptic ion channels has hitherto been limited to large specialized terminals such as the calyx of Held or hippocampal mossy fiber bouton. The electrophysiology and ion-channel complement of far more abundant small synaptic terminals (≤1 μm) remain poorly understood. Here we report a method based on superresolution scanning ion conductance imaging of small synapses in culture at approximately 100–150 nm 3D resolution, which allows presynaptic patch-clamp recordings in all four configurations (cell-attached, inside-out, outside-out, and whole-cell). Using this technique, we report presynaptic recordings of K +, Na +, Cl −, and Ca 2+ channels. This semiautomated approach allows direct investigation of the distribution and properties of presynaptic ion channels at small central synapses.
Novak and colleagues have developed a method for nanoscale-targeted patch-clamp presynaptic recordings in submicrometer central synapses identified using superresolution scanning ion conductance microscopy. This semiautomated approach opens a new window on the physiology of small presynaptic terminals.