All-optical reporting of inhibitory receptor driving force in the nervous system

Abstract

Abstract Ionic driving forces provide the net electromotive force for ion movement across receptors, channels, and transporters, and are a fundamental property of all cells. In the nervous system, fast synaptic inhibition is mediated by chloride permeable GABA A and glycine receptors, and single-cell intracellular recordings have been the only method for estimating driving forces across these receptors (DF GABAA ). Here we present a tool for quantifying inhibitory receptor driving force named ORCHID: all-Optical Reporting of CHloride Ion Driving force. We demonstrate ORCHID’s ability to provide accurate, high-throughput measurements of resting and dynamic DF GABAA from genetically targeted cell types over multiple timescales. ORCHID confirms theoretical predictions about the biophysical mechanisms that establish DF GABAA , reveals differences in DF GABAA between neurons and astrocytes, and affords the first in vivo measurements of intact DF GABAA . This work extends our understanding of inhibitory synaptic transmission and demonstrates the potential for all-optical methods to assess ionic driving forces.

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