Biological complexity: sensory receptors everywhere (Introduction)

by David Turell , Friday, September 16, 2016, 15:40 (2990 days ago) @ David Turell

Not just where they are expected to be: - http://www.the-scientist.com/?articles.view/articleNo/46831/title/What-Sensory-Receptor... - " In 2012, Johns Hopkins University's Berkowitz had just moved to a lab space where the lights were motion-activated, and his postdoc Gautam Sikka soon began to observe a curious response in the blood vessels he had isolated for study: whenever he walked in and the lights turned on, the vessels exerted less pressure on the force transducer the researchers had attached to constantly stream data. - "A literature search revealed that the relaxation of blood vessels in response to light, called photorelaxation, had been described almost 50 years earlier, but the underlying mechanisms had never been fully elucidated. Berkowitz wondered if these effects were mediated by resident light-sensing pigments. If so, it wouldn't be the first time that a sensory receptor had been found outside of a sense organ. - "The light, odor, and taste receptors located in our eyes, noses, and tongues flood our brain with information about the world around us. But these same sensory receptors are also present in unexpected places around the body, where they serve a surprising range of biological roles. In the last decade or so, researchers have found that the gut “tastes” parasites before initiating immune responses, and the kidneys “smell” fatty acids, regulating blood pressure in response. Sure enough, upon further investigation Berkowitz found that it was melanopsin, a light-sensing pigment that serves circadian entrainment and other nonvisual functions in the eye, that modulated the relaxation of blood vessels when the lab lights came on. - "In contrast to the early days of the field, the idea of sensory receptors outside of sensory organs is no longer unusual. “They're all just chemoreceptors, and you can use them in lots of different contexts in physiologically different systems,” says University of Colorado Denver neurobiologist Thomas Finger. - "Now researchers are characterizing such sense receptors present in different tissues around the body and working to understand their functions, with the eventual goal of using these receptors for various diagnostic or therapeutic applications." - Comment: A very long article, telling about all the different studies, follows the above excerpt. Here is an example, very complex: - "In a few cases, researchers may have identified the natural ligands responsible for activating olfactory receptors around the body. In the kidney, for example, Johns Hopkins University's Pluznick found that certain short-chain fatty acids produced by gut bacteria can activate olfactory receptor 78 (Olfr78), which in mice triggers changes in blood pressure. When researchers injected mice lacking the gene for Olfr78 with short-chain fatty acids, the animals' blood pressure dropped, suggesting that Olfr78 by itself normally increases blood pressure in response to the compounds. But blood pressure regulation is complicated, and Pluznick found another, nonolfactory receptor called Gpr41 that decreased blood pressure in response to short-chain fatty acids and had a stronger effect than Olfr78.8 Pluznick suggests that the two receptors might act together to produce a buffering effect that protects against wild swings in blood pressure as fatty-acid levels fluctuate."