Chili is the "soul" of Mexicans; we can't imagine our food without it. But what does chili have to do with pain? A lot: the physiological responses to "chili bite" are sweating, mucus, burning, tearing, numbness, diarrhea, and even pain, when we eat it in excess, explained Tamara Rosenbaum Emir, a researcher at UNAM's Institute of Cell Physiology (IFC).
It happens in this way because an ion channel called TRPV1 opens in neurons, which "activates" the pain that can be produced when we eat a hot meal. But this receptor is also involved in inflammation, neuropathic pain, angina pectoris, arthritis, and cancer; its main function is to warn that something is wrong - from eating too much chili to having bone cancer, for example - and that we should go to the doctor.
In the world, several research groups have devoted themselves to understanding how these receptors work, which is important for the detection of pain caused by diseases, said the scientist before María Soledad Funes Argüello, director of the IFC; and María Dolores Valle Martínez, general director of the National Preparatory School.
During the inaugural conference of Brain Week at the IFC, Tamara Rosenbaum recalled: although Mexico is considered the country of origin of the chili bell pepper, it came from South America, between Bolivia and Brazil. It is a solanaceous plant; tomato, potato, and tobacco, for example, also belong to this family.
Chili plants belong to the Capsicum genus. Three species, in particular, are cultivated in our country: C. annuum (jalapeño, serrano, poblano, and morrón); C. chinense (habanero); and C. pubescens (apple), she added in the Antonio Peña Díaz auditorium of this academic institution.
The scientist pointed out that chili has been domesticated for eight thousand years; since prehistoric times, a selection and several crosses of the plant have been made, and it is used continuously, she mentioned before students of the university baccalaureate.
In the lecture What do hot peppers have to do with pain? he added that we explore the world through the senses. "We have all felt pain, that subjective experience that produces an unpleasant sensation."
There are two important survival capacities for organisms: detecting temperature changes (thermoception) and pain (nociception), and we achieve this quickly to move away from situations that could harm us, she explained.
Pain helps us to know that we are sick or that we have hurt ourselves, but some syndromes prevent us from detecting it; for example, people can cut their fingers without realizing it. That is why feeling it is important, as a survival capacity, he said.
This process is possible due to the communication between certain types of neurons, which allow electrical signals to pass at a very fast speed. "These cells have lipid bilayers to protect themselves; certain types of positively or negatively charged molecules, called ions, must move in these membranes. And for these to move through that layer, you need structures that allow them to pass through: water-filled pores called ion channels."
These are water pores that open and close in a regulated way; there are hundreds of different types of ion channels that respond to different aspects, and make it possible to generate that electricity that, in this case, allows us to move away from danger.
In other words, ion channels allow us to detect stimuli, including those that harm us. Their activity explains how we can perceive cold and heat, or how we have molecules that respond to pain and "chilor".
A family of ion channels called transient receptor potentials, or TRPs, have among their functions to be receptors for noxious stimuli; among them are the thermosensitive TRPs that are activated by the substance present in chili peppers, called capsaicin, noted Rosenbaum Emir.
Although we associate chili peppers with pain, we continue to eat them, but why? Because when we eat it endorphins are released in our brain, the same ones that are secreted when we run or do other exercises and make us feel happy. Therefore, "chili has an almost addictive characteristic".
Wilbur Scoville, an American scientist, created a scale to determine how hot a chili bell pepper is; the number of units indicates the amount of capsaicin each one contains. The hottest, according to the Guinness Book of Records, is the Carolina reaper, which is not natural but was achieved through crossbreeding.
It is known that the activation of TRPV1 by capsaicin produces pain through experiments with genetically modified mice that do not have the receptor and do not respond to this substance, said the expert.
It is also known that we mammals get irritated, but birds do not, because ion channels are like jigsaw puzzles made up of different pieces, and if one of them is missing, they do not work. To activate and open the pore, the "key" and the "lock" must be very exact; and birds lack an amino acid to open those channels.
Tamara Rosenbaum commented that when we get chili bites the worst thing we can do is eat hot soup, or drink tequila with lemon; instead, we should drink milk or eat butter.