Changes in extrinsic fluorescence in squid axons during voltage-clamp.

Fluorescence changes in squid axons were examined after staining with rhodamine B, pyronin B, or 8-anilinonaphthalene-1-sulfonate by intracellular application. Gradual changes in fluorescence were detected during both hyperpolarizing and depolarizing voltage-clamp pulses. Abrupt changes were often observed at the onset and at the end of voltage-clamp. Possible sources of artifact in optical measurements of this type and some implications of the findings are discussed.