Functional imaging within individual pain fibres ex vivo with optical microscopy.

Here we introduce a simple experimental approach for studying afferent pain fibre physiology. We have developed a mouse en bloc dural-skull preparation for optical microfluorometric imaging to directly study the physiological functioning in selectively identified, individual nociceptive fibre free nerve endings. Functional optical imaging using widefield epifluorescence microscopy was combined with electrophysiological stimulations, pharmacological manipulations, and the UV photolysis of caged compounds. For the first time, we show high-resolution functional imaging of single action potential-evoked fluorescent transients, as well as sub- and supra-threshold calcium signaling events within individual nociceptive fibre terminations. This novel experimental approach opens up a new window for studying nociceptive fibre physiology and pathophysiology.