A description regarding the use of chemical tools to evaluate neuroreceptors and ion channels is given which focuses on recent studies and the interplay between functional studies which are done on real mammalian receptors and the structural studies of model systems. Topics being discussed include: Cys-loop neuroreceptors; structural models; unnatural amino acid mutagenesis which enables chemical-scale studies. Under chemical-scale studies are: the binding site; the gating interface; and the gating switch.