1. The Clayton Foundation Laboratories for Peptide Biology, The Salk Institute, La Jolla, California 92037, Ferring Research Institute Inc., 3550 General Atomics Court, Building 2, Room 442, San Diego, California 92121, Divisions of Neuroscience and Reproductive Sciences, Oregon National Primate Research Center, Beaverton, Oregon 97006, and Departments of Physiology and Pharmacology and Cell and Developmental Biology, Oregon Health and Science University, Portland, Oregon 97239