The human body has about 1,000 kinds of such receptors, structures on the surface of cells, which let the body respond to a wide variety of chemical signals, like adrenaline. (relevantmagazine.com)
Such receptors allow insects to identify members of their own species. (scientificamerican.com)
In cell cultures, the presence of nicotine seemed to increase the number of such receptors present, but also numbed some of them. (sciencemag.org)