Measuring Absolute Membrane Potential Across Space and Time.

Membrane potential (V mem ) is a fundamental biophysical signal present in all cells. V mem signals range in time from milliseconds to days, and they span lengths from microns to centimeters. V mem affects many cellular processes, ranging from neurotransmitter release to cell cycle control to tissue patterning. However, existing tools are not suitable for V mem quantification in many of these areas. In this review, we outline the diverse biology of V mem , drafting a wish list of features for a V mem sensing platform. We then use these guidelines to discuss electrode-based and optical platforms for interrogating V mem . On the one hand, electrode-based strategies exhibit excellent quantification but are most effective in short-term, cellular recordings. On the other hand, optical strategies provide easier access to diverse samples but generally only detect relative changes in V mem . By combining the respective strengths of these technologies, recent advances in optical quantification of absolute V mem enable new inquiries into V mem biology.