At present, although there are steroidal medications that reduce local inflammatory reactions and local anesthetics that block sensory nerver fibers, there are no medications that act directly to suppress the sensation of itch by inhibiting the response of the itch-signating receptors that innervate the skin. In spite of the fact that there is a potentially large market for such products, there is no evidence that pharmaceutical companies are devoting much effort toward developing such products. Unlike pain research where there are well developed animal and human models for the assessment of pain inhibition, quantitative measures of the intensity of acute pruritus are only beginning to be constructed. The purpose of this proposal is to develop an animal behavioral model that can be used to evaluate antipruritic compounds and then to test the model's ability to discriminate between treatment and control trials when a local anesthetic is administered in double blind tests. The use of histamine, which presumably acts directly on the sensory nerve terminals, as a pruritic stimulus has been very encouraging in preliminary experiments. In Phase II of this project, the animal model will be used to test a number of herbal preparations that are reported to inhibit pruritus. In addition, there are indications that pharmaceutical companies will become more interested in developing antipruritic medications after a method of assay has been developed.
