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There are both cold and hot receptors of temperature which use TRP ion channels. When a certain temperature is achieved one of the TRP channel is opened and Ca2+ ions enter the first order neuron, enter image description here

My question is that if several types of TRP ion channel are present on this neuron, how does the neuron differentiate mildly hot temperature from very hot temperature?

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  • $\begingroup$ Welcome. Can you add the source of the figure you included? Do you have a clue what the answer might be to this question? I mean, there are differences between the receptor activations, so what do you think might be going on here? Please edit the question by including the source of the image and an attempt to your answer $\endgroup$
    – AliceD ♦
    Commented Jul 17 at 7:03

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I´d say that this is just for presentive purposes. Heat activated neurons will mainly express one TRP-receptor type and show activity at this specific temperature range.

I did not find publications that show coexpression of all of those receptors except for TRPM8, TRPA1, TRPV 2 with TRPV1 ("TRPV1 was expressed in 29% of TRPM8-positive cells in dorsal root ganglion sections"-https://pubmed.ncbi.nlm.nih.gov/15050705/ , "TRPV1 is coexpressed on the vast majority of TRPA1-expressing sensory nerves "-https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3417484/ , "significant co-expression was seen in 20.7% of TRPV2-positive neurons"-https://journals.lww.com/neuroreport/abstract/2003/12020/co_expression_of_heat_sensitive_vanilloid_receptor.23.aspx )

Here some quotes from another paper that would corroborate that: "Some fibres respond to a moderate threshold (∼43°C), whereas a smaller percentage respond to high-threshold (∼52°C)" "observed that cutaneous warm fibres of the hairy skin of primates could be divided into two groups"..."However, one group of neurons had an average maximum response at 41°C, whereas the second group continued to increase its firing rate above this temperature." https://www.nature.com/articles/nrn1141

(But if it were the case that there were multiple receptors one hypothetical way of discriminating between different receptors would be the intensity of activation which can change the frequency of action potentials,that might be higher for one receptortype due to higher ion conductance,or all receptors together might be active at once at certain temperature)

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  • $\begingroup$ I think this answer overemphasizes firing at a specific temperature, which isn't really how these neurons code. Your uncited parenthetical paragraph at the end is more representative. $\endgroup$
    – Bryan Krause ♦
    Commented Jul 17 at 12:23
  • $\begingroup$ This sentence is a contradiction: "I did not find publications that show coexpression of multiple of those receptors, though there are some that can occur together on the same neuron" $\endgroup$
    – Bryan Krause ♦
    Commented Jul 17 at 12:24

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