These findings illustrate the broad evolutionary tuning of TRP channels as thermosensors in the vertebrate nervous system. Thus, snakes detect infrared signals through a mechanism involving radiant heating of the pit organ, rather than photochemical transduction. TRPA1 orthologues from pit bearing snakes (vipers, pythons, and boas) are the most heat sensitive vertebrate ion channels thus far identified, consistent with their role as primary transducers of infrared stimuli. Here we use an unbiased transcriptional profiling approach to identify TRPA1 channels as infrared receptors on sensory nerve fibers that innervate the pit organ. How this organ detects and transduces infrared signals into nerve impulses is not known. Infrared signals are initially received by the pit organ, a highly specialized facial structure that is innervated by nerve fibers of the somatosensory system. Snakes possess a unique sensory system for detecting infrared radiation, enabling them to generate a ‘thermal image’ of predators or prey. Hollopeter, Gunther Chesler, Alexander T. Molecular Basis of Infrared Detection by Snakes The properties of these snake TRPA1s raise intriguing questions about the mechanisms responsible for the exceptional sensitivity of many biological thermoreceptors and about the evolutionary origins of these warmth-activated TRP channels. New evidence shows that pit organs respond to temperature using the warmth-activated cation channel TRPA1 (transient receptor potential ankyrin 1), a finding that provides a first glimpse of the underlying molecular hardware. It has been theorized that this capacity reflects the pit organ's exceptional sensitivity to subtle fluctuations in temperature, but the molecules responsible for this extreme thermal resolution have been unknown.
The pit organs of pit vipers, pythons, and boas are remarkable sensory devices that allow these snakes to detect infrared radiation emitted by warm-blooded prey. Panzano, Vincent C Kang, Kyeongjin Garrity, Paul A Infrared snake eyes: TRPA1 and the thermal sensitivity of the snake pit organ.
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