GOLGI-LIKE LABELING OF A SINGLE NEURON RECORDED EXTRACELLULARLY

We describe a novel and powerful extracellular method for the staining of a single neuron identified by electrophysiological criteria. This single-unit technique involves the use of glass micro-electrodes (tip diameter: 1.5-2.5 mu m) filled with a saline solution (NaCl; 0.5 M) co ntaining 1.5% of biocytin or Neurobiotin. Once a neuron is recorded, i solated and identified, the tracer is delivered by anodal current puls es of a few nA. The cell must remain well isolated and alive during th e ejection procedure to ensure optimal staining. Evidence is provided that the labeled neuron is actually the one that was recorded. Our sim ple method is reliable with a success rate exceeding 85%. The advantag es and pitfalls are discussed. This single-unit labeling technique cou ld further be combined with any other procedures ranging from biologic al to behavioral studies.