Thinking of Co 2+ ‐staining explant tissue or cultured cells? How to make it reliable and specific

Ca 2+ and/or Zn 2+ entry into neurons and glial cells is often a key step driving the processes of neurodevelopment and disease. As a result, a major pre‐occupation of many neuroscientists has been in tracking down when and where nervous tissues express ion channels with appreciable divalent ion permeability. The cobalt (Co 2+ )‐staining technique is one of the few techniques that allow a snapshot of the entire neuronal circuit, and selectively labels cells expressing divalent‐permeable ion channels with a brown–black precipitate. Despite this, its use has been remarkably limited in the past decade. Reluctance to employ this approach has largely been related to an earlier concern with obtaining a reliable and reproducible means of visualizing transported Co 2+ . Here we show that recent advances have resolved these issues, opening this straightforward and valuable technique to a much larger neuroscience audience.