Ramon Latorre and Ignacio Díaz-Franulic; PNAS January 4, 2022 119 (1) e2121015119

Three apparently unrelated findings led to the discovery of the temperature receptors: a better understanding of pain-sensing, the molecular nature of the channels in charge of touch and proprioception, and the 2021 Nobel Prize in Physiology or Medicine bestowed to David Julius and Ardem Patapoutian.

In 1953, state-of-the-art research in temperature sensing concluded that temperature afferent fibers came in two flavors, “cold” and “warm,” characterized by discharging by a lowering in temperature and an increase in temperature, respectively (1). Hensel and Zotterman had previously described the sensitizing effect of menthol upon cold receptors (2). It is also an old observation that acute application of capsaicin, the active component of chili peppers, causes intense pain, and that its repeated administration renders animals insensitive to the action of this vanilloid compound (3). The fact that capsaicin induces a depolarization of ventral root neurons from the isolated rat spinal cord suggested to Theriault et al. (4) that capsaicin’s acute and chronic effects on nociception could be explained by a direct action on primary sensory neurons. On the other hand, McCarter et al. (5) demonstrated the existence of mechanosensitive currents in rat dorsal root ganglion (DRG) cells, clearly pointing to the existence of mechanosensitive ion channels as being responsible for the sense of touch.

By discovering the molecular transducers underlying the senses of temperature and touch, the 2021 Nobel laureates in Physiology or Medicine increased greatly our understanding of how the nervous system codes sensory information.

See https://www.pnas.org/content/119/1/e2121015119