TrpM8-mediated somatosensation in mouse neocortex.

Area of Science:

• Neuroscience
• Somatosensation Research
• Sensory Perception

Background:

• Somatosensation involves diverse peripheral neural subtypes.
• The cortical mapping of pain and temperature sensation remains debated.
• TrpM8 receptors mediate cool sensation.

Purpose of the Study:

• Investigate the neural substrate for cool perception in the mouse neocortex.
• Identify neocortical areas responsive to cool somatosensory input.
• Utilize TrpM8 receptor activation for mapping cool sensation pathways.

Main Methods:

• Stimulated cutaneous TrpM8 receptor-expressing neurons using menthol, a selective agonist.
• Developed a broad-scale brain survey method quantifying c-fos immunoreactivity (fos-IR).
• Compared brain activation in wild-type and TrpM8-knock-out mice.

Main Results:

• Menthol stimulation elevated fos-IR in the posterior insular cortex, secondary somatosensory cortex (S2), and primary somatosensory cortex (S1).
• Anterior brain regions like the piriform cortex, amygdala, and hypothalamus also showed menthol-induced fos-IR.
• Menthol-mediated activation was absent in TrpM8-knock-out animals, confirming pathway specificity.

Conclusions:

• Cool somatosensory input broadly activates neural activity across the mouse brain.
• The posterior insula, S2, and S1 are key neocortical areas for processing cool sensation.
• Findings align with human studies implicating the posterior insula in temperature and somatosensory encoding.