Methods for identifying modulators of receptor activity using orthologues of human receptors are described. Additionally, a method for identifying an animal model useful in the screening of potential therapeutic agents is provided. The genes for bradykinin B₁ receptors from five mammalian species, vervet monkey, rhesus macaque, tree shrew, dog and pig, as well as the genes for CXCR2 receptors from chimpanzee, gorilla, orangutan, rhesus, vervet and baboon have been cloned and characterized and are described herein.