Targeted axon-attached recording with fluorescent patch-clamp pipettes in brain slices

Understanding the physiology of axons in the central nervous system requires experimental access to intact axons. This protocol describes how to perform cell-attached recordings from narrow axon fibers (phi < 1 mu m) in acute and cultured brain slice preparations (with a success rate of similar to 50%). By using fluorophore-coated glass pipettes and Nipkow disk confocal microscopy, fluorescently labeled axons can be visually targeted under online optical control. In the cell-attached configuration, axonal action potentials are extracellularly recorded as unit-like, sharp negative currents. The axon morphology labeling and cell-attached recordings of axons can be completed within 1-2 h. The recordings are stable for at least 30 min.