Profound alteration in cutaneous primary afferent activity produced by inflammatory mediators

Area of Science:

• Neuroscience
• Pain Research
• Sensory Biology

Background:

• Inflammatory pain involves altered nociceptor transmission and 'silent' afferent recruitment.
• Understanding these changes is crucial for developing effective pain therapies.

Purpose of the Study:

• To investigate inflammation-induced changes in cutaneous sensory neuron mechanosensitivity in vivo.
• To determine the role of 'silent' afferents in inflammatory pain.

Main Methods:

• Generated mice expressing GCaMP3 in cutaneous sensory neurons.
• Imaged neuronal responses to mechanical stimulation before and after inflammatory soup (IS) infusion in unanesthetized mice.
• Evaluated the effect of brief heating prior to IS infusion.

Main Results:

• IS infusion rapidly altered mechanical responsiveness in most neurons.
• More neurons lost sensitivity than gained it; 'silent' afferents gaining mechanosensitivity were rare.
• Heating skin before IS infusion increased the recruitment of formerly 'silent' afferents by fivefold.

Conclusions:

• Inflammation-induced pain results from a dynamic shift in sensory input balance.
• Both loss and gain of neuronal sensitivity contribute to altered pain perception.
• Thermal priming can enhance the recruitment of 'silent' afferents, influencing pain signaling.