ABSTRACT
1. Using an optical method for measuring membrane potential, we have been able to monitor action-potential activity simultaneously in 14 neurons of the supraesophageal ganglion of the barnacle. 2. Under favorable conditions, 4-mV synaptic potentials could also be detected optically.
Subject(s)
Central Nervous System/physiology , Thoracica/physiology , Action Potentials , Animals , Central Nervous System/cytology , Electronics, Medical , Methods , Neurons/physiologyABSTRACT
The absorption, fluorescence, dichroism, and birefringence of stained squid axons were measured during action potentials and voltage clamp steps in an effort to find large optical signals that could be used to monitor membrane potential. Changes in all four optical properties were found that were linearly related to membrane potential and, with several new dyes, the signal-to-noise ratios were larger than any obtained previously. The problem of photodynamic damage was greatly diminished; with a merocyaninerhodanine dye, the photodynamic damage associated with intense light and the presence of oxygen was negligible. The absorption change obtained with this dye was relatively large; it could be measured with a signal-to-noise ratio of 100:1 during a single action potential.
