This proposal describes the continuation of our research efforts in the areas of (a) identification of mammalian pheromones: (b) testing of putative pheromones for various endocrine and behavior effects; (c) isolation of the pheromone-binding proteins and their sequencing through mass spectrometry; (d) in-depth studies of the pheromone/protein interactions by spectroscopic means (NMR spectrometry, in particular); (e) characterization of the receptor proteins isolated from the vomeronasal tissues; and (f) searching for the biochemical origin of the rodent pheromones. The specific olfactory messengers called pheromones will be studied predominantly in the house mouse and the rat and, to a lesser degree, in deermice and hamsters. The previously identified mouse pheromones will be used in the binding (in-depth) studies by NMR as selective ligands to the recombinant versions of the pheromone- binding proteins. The isotopically labeled precursors of pheromones will be incubated in appropriate tissue media, followed by mass- spectrometric detection of a pheromone with an incorporated stable isotope. Putative pheromones of the rats, deermice, and hamsters will be synthesized and tested for the endocrinological activities (estrus synchronization and puberty delay) and a variety of behavioral effects. The proposed studies provide unique opportunities to understand the molecular mechanisms of olfaction, one of the most important sensory functions in humans. Also, rodents have been used extensively as convenient models in much biomedical research. Understanding the aspects of chemical communication in the species could also be important in a population control of wild rodents.