Nanoscale-Targeted Patch-Clamp Recordings of Functional Presynaptic Ion Channels

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 mu m) 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 Ca2+ channels. This semiautomated approach allows direct investigation of the distribution and properties of presynaptic ion channels at small central synapses.