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How do menthol and capsaicin produce sensations of cold and heat?
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Thermoreception
Warm-blooded animals, such as polar bears, maintain stable body temperatures and adapt to substantial geographic and seasonal temperature fluctuations. Thermal adaptation is supported by the function of sensory structures called thermoreceptors.
Menthol and capsaicin produce sensations of cold and heat by acting as chemical stimuli for specific transient receptor potential (TRP) channels, which are specialized ion channels located on sensory neurons.123
- Capsaicin and Heat: Capsaicin, the pungent compound found in red peppers, binds to and activates the TRPV1 receptor. Because TRPV1 is a heat-sensing ion channel, its activation by capsaicin mimics the physiological response to thermal stimulation, resulting in the sensation of heat or burning pain.23
- Menthol and Cold: Menthol acts on the TRPM8 receptor, which is a cold-sensing ion channel. By binding to TRPM8, menthol triggers the same neural pathways that are normally activated by cooling, thereby creating the illusion of a cold sensation.21
These receptors are part of a broader system of thermoreceptors that allow the nervous system to detect and respond to temperature changes. The discovery of these molecular mechanisms, largely attributed to the work of physiologist David Julius, has significantly advanced our understanding of how chemical compounds can influence somatosensation.12