There is increasing evidence that oxytocin (OT) and arginine-vasopressin (AVP), two neuropeptides released in the brain, play important roles in social behaviors. Several studies have supported the involvement of these neuropeptides in autism spectrum disorders (ASDs). Children with ASDs have been found to have lower blood levels of OT, and genetic studies of ASD patients have found associated mutations in genes encoding OT and AVP receptors. As well, treating adults with ASDs by administration of OT has been shown to improve social skills and reduce repetitive behaviors. Despite this evidence, little is known about the neuronal networks responsible for producing and releasing OT and AVP in the brain. Studying how these neurons develop and function in the brain regions that control social behavior may be essential for understanding the basis of social deficits in ASDs. In this research, Dr. Wagner and colleagues will develop a genetically modified mouse designed to facilitate the study of the OT- and AVP-producing neuronal network. They will generate several lines of mice in which the neurons that produce OT and AVP are genetically labeled by the expression of fluorescent proteins, allowing them to be easily observed and manipulated. These mice will be invaluable for examining the structure, physiology, and function of the neural networks involving these neurons, and will provide new methods for manipulating the viability, activity, and connectivity of these neurons. Dissecting the functions of the OT and AVP-producing neurons in an animal model will improve our understanding of the neural networks underlying social behaviors, and will provide a basis for parallel research in the roles of these networks and neuropeptides in people with ASDs.