Hot and Cool Taste Sensations The sensations of heat and cold are transduced by
ID: 1045448 • Letter: H
Question
Hot and Cool Taste Sensations
The sensations of heat and cold are transduced by a group of temperature-gated cation cannels. For example, TRPV1, TRPV3, and TRPM8 are usually closed, but open under the following conditions: TRPV1 at ³ 43oC; TRPV3 at ³ 33oC; and TRPM8 at <25oC. These channels are expressed in sensory neurons known to be responsible for temperature sensation.
Propose a reasonable model to explain how exposing a sensory neuron containing TRPV1 to high temperature leads to a sensation of heat. (Hint: TRPV1 opening influxes Na+ and Ca2+). Your answer should include words “depolarization” and “action potential”.
Capsaicin, one of the active ingredients in “hot” peppers, is an agonist of TRPV1. Capsaicin shows 50% activation of the TRPV1 response (i.e. EC50) at a concentration of 32nM. Explain why even a very few drops of hot pepper sauce can taste very “hot” without actually burning you.
Menthol, one of the active ingredients in mint, is an agonist of TRPM8 (EC50 = 3mM) and TRPV3 (EC50 = 20mM). What sensation would you expect from contact with low levels of menthol? With high levels?
Explanation / Answer
A) The TRP1 channel is opened up on account of heat, which leads to an influx of cations into the sensory neuron. This depolarizes the membrane and generates an action potential. Further, downstream signaling of the neurons result in the release of neurotransmitters that tells that heat has been sensed.
B) The response to actual heat is mimiced by the response to capsaicin, which causes the channel to open at a lower temperature, than the normal. The very low EC50 of capsaicin indicates that even a small amount of capsaicin taken would have a large effect, which would further result in false sensation of heat.
C) When the menthol levels are low, the TRPM8 channel would open, giving a cool sensation. And, when menthol levels are high, then both TRPM8 and TRPV3 channels would open, giving a mixed sensation of hot and cool.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.