Abstract
Oxytocin is a peptide hormone synthesized and released from the hypothalamus for regulation of maternal behaviors, social cognition, and other physiological processes. Oxytocin is part of a family of neurohypophysial nonapeptides, which are evolutionarily ancient and found in many vertebrate and invertebrate species. Oxytocin or oxytocin analogs have been shown to regulate forms of social behavior, particularly those related to reproduction and maternal care of offspring.
Classically, oxytocin supports two main functions: lactation and parturition. Oxytocin signaling in mammary glands is required for milk letdown and the milk ejection reflex, and is important for uterine contractions by acting on the myometrium (smooth muscle of the uterine walls). Oxytocin signaling occurs within the central nervous system, affecting maternal and paternal behaviors, pair bond formation, and social cognition or neural function in general.
This chapter describes the action of oxytocin within the body and brain. The first section provides a historical overview, discussing how methodological developments enabled discoveries of the structure and function of oxytocin, as well as the circuitry for oxytocin secretion and signaling. The organization of the hypothalamic oxytocin system is outlined and a number of physiological processes modulated by or requiring oxytocin are described in more detail. This includes several potentially important gender-specific differences in the mammalian oxytocin system, including those identified in humans. Some of the most important functions and gender differences of oxytocin relate to synaptic transmission and neuroplasticity involved in social cognition and maternal behavior, which to date have mainly been examined experimentally in rodents. Many aspects of oxytocin signaling remain unclear, and this chapter concludes with some speculation as to future directions for research into this important peptide system.