Characterization of Tachykinin Receptors in Human and Rat Skin

Receptors for the tachykinin family of peptides were investigated in human and rat skin areas using quantitative receptor autoradiography and emulsion autoradiography with 125I-Bolton-Hunter substance P (125I-BH-substance P), a non-selective radioligand, and 125I-Bolton-Hunter eledoisin (125I-BH-eledoisin), a selective radioligand for the tachykinin NK-2 receptor. There were no differences between localization of specific 125I-BH-substance P and 125I-BH-eledoisin binding sites in human and rat skin. The highest densities of the binding sites were in the dermal papillae of the human finger pad skin and the rat paw pad skin. In cold-ligand saturation experiments done in the presence of increasing concentrations of unlabeled substance P, 125I-BH-substance P binding to the rat and human dermal papillae was single and of a high affinity. 125I-BH-eledoisin bound to the dermal papillae with a much lower affinity than 125I-BH-substance P did. The rank order of potency of unlabeled tachykinin peptides to displace 125I-BH-substance P binding to the dermal papillae of the human finger pad skin and rat paw pad skin was substance P > eledoisin > neurokinin A >> neurokinin B. Thus, the methods we used revealed that the tachykinin NK-1 receptor is predominantly present in the skin dermal papilla