GFP is a selective non-linear optical sensor of electrophysiological processes in Caenorhabditis elegans

Electrophysiology of the nematode Caenorhabditis elegans has the potential to bridge the wealth of information on the molecular biology and anatomy of this organism with the responses of selected cells and cellular neural net works associated with a behavioral response. In this paper we report that t he nonlinear optical phenomenon of second harmonic generation (SHG) can be detected using green fluorescent protein (GFP) chimeras expressed in select ed cells of living animals. Alterations in the SHG signal as a result of re ceptor ligand interactions and mechanical stimulation of the mechanosensory cells indicate that this signal is very sensitive to membrane potential. T he results suggest that this approach to membrane potential measurements in C. elegans and in other biological systems could effectively couple data o n selective locations within specific cells with functional responses that are associated with behavioral and sensory processes.