Chapter 11 - Presence and Absence of Sex Differences in Structure and Function of the Brain Oxytocin System: Implications for Understanding the Regulation of Social Behavior

Abstract

The oxytocin (OT) system in the brain is an important modulator of social behavior in mammals, including humans. Here, we provide a comprehensive review in which we discuss the evidence showing sex differences, or lack thereof, in structure and function of the brain OT system parameters in rodents and humans. We find that (1) the reported sex differences in the brain OT system are not ubiquitous, but appear to be highly species-specific and (2) actions of the OT system on behavior and neuronal responses are often sex-specific, but do not necessarily correspond with sex differences in OT system parameters. Based on these findings, we propose that sex differences in the brain OT system depend on species-specific social organizations (i.e., mating, parental, and sociality systems) and discuss sex-specific actions of OT on behavior and neuronal responses in the context of differences in social organizations. Furthermore, OT may show promise in the treatment of social dysfunction in neuropsychiatric disorders, many of which show sex differences in prevalence and treatment responses. We therefore discuss recent advances and precautions of OT as a therapeutic agent in the treatment of social dysfunction in both men and women. Overall, we find that there is limited research investigating the effects of OT on behavior and brain responses in males and females in the same design, highlighting the need for comparative research, particularly if OT is to be used as a therapeutic agent in both sexes. Given the many studies indicating a role of the brain OT system in sex-specific regulation of social behavior, an important next step will be to investigate how these effects are mediated and how they relate to the presence or absence of sex differences in brain OT system parameters.