title: Fluorescence monitoring of electrical responses from small neurons and their processes.
abstract: To improve the sensitivity of fluorescence measurements of electrical responses from small cells and their processes, we have optimized the optical measuring system. The fluorescence intensity from a stained cell was increased 40-fold relative to our previous apparatus. The increased fluorescence intensity permits the use of an inexpensive photodiode (or a photodiode array) that has a approximately 10-fold higher quantum efficiency relative to a photomultiplier. Utilizing the improved apparatus, we optically recorded an action potential of a 2 microns wide neuronal process with a signal-to-noise ratio of approximately 50 (root mean square noise) without averaging. We also report the design of an improved fluorescence voltage-sensitive probe; the fractional change of the fluorescence signal under optimal conditions was 21%/100 mV.
mesh_terms: D000818:Animals; D002460:Cell Line; D004553:Electric Conductivity; D008564:Membrane Potentials; D051379:Mice; D009374:Neoplasms, Experimental / Q000503:physiopathology; D009447:Neuroblastoma / Q000503:physiopathology*; D009474:Neurons / Q000502:physiology*; D013050:Spectrometry, Fluorescence / Q000379:methods