Although the vomeronasal system is structurally similar to the olfactory system, its functional significance is poorly understood. Although behavioral roles and anatomical organization of the vomeronasal system have been extensively investigated in rodents and squamate reptiles, the physiological properties and odorant responsitivity of the receptor cells have not been thoroughly examined in any species. Because the vomeronasal system had its evolutionary origin in early amphibians, a careful examination of its function in modern amphibians would provide a valuable contribution to our overall understanding of the physiological and behavioral roles of the system. This project serves as the starting point for a series of studies to elucidate the physiological response properties of vomeronasal receptor cells in the axolotl (Ambystoma mexicanum), an aquatic salamander, with the long-term objective of understanding the function of the vomeronasal system in amphibians. The goal of the current study is to examine the mechanisms by which the activity of vomeronasal receptor cells is modulated by odorants and endogenous hormones. In the proposed experiments, the voltage-dependent conductances in axolotl vomeronasal receptor cells will be characterized using whole-cell patch recording methods. The possible modulation of electrical activity in vomeronasal receptor cells by gonadotropin releasing hormone (GnRH) will be explored. Finally, the sensitivity of vomeronasal receptor cells to a variety of odorants will be assessed, and the modulation of specific membrane conductances by odorants will be characterized.