Second-harmonic generation voltage imaging at subcellular resolution in rat hippocampal slices

Area of Science:

• Neuroscience
• Biophysics

Background:

• Action potentials (APs) are crucial for neuronal signaling and information processing.
• Investigating dendritic AP propagation is vital for understanding neuronal function.
• Traditional electrode techniques limit AP studies to proximal neuronal compartments.

Purpose of the Study:

• To explore the utility of voltage-sensitive dyes (VSD) for measuring AP propagation in distal dendrites and spines.
• To evaluate second-harmonic generation (SHG) as a voltage-sensing mechanism using VSDs.
• To compare SHG with fluorescent imaging for VSD-based voltage measurements.

Main Methods:

• Utilized membrane-bound organic voltage-sensitive dyes (VSD).
• Employed both fluorescent imaging and second-harmonic generation (SHG) imaging.
• Measured voltage changes in oblique dendrites and dendritic spines.

Main Results:

• VSDs allow voltage change measurements in previously inaccessible dendritic compartments.
• SHG provides a linear response to membrane potential changes across different cell compartments.
• SHG exhibits a voltage sensitivity exceeding 10% per 100 mV.
• Current SHG methods show a lower signal-to-noise ratio compared to fluorescent imaging.

Conclusions:

• VSDs combined with SHG offer a novel approach for studying dendritic AP propagation.
• SHG's linear voltage response is advantageous for quantitative analysis of membrane potential.
• Further optimization is needed to improve the signal-to-noise ratio of SHG for broader application.