EVOLUTION. Dissecting diversity in the social brain

Oxytocin, Dopamine, and Opioid Interactions Underlying Pair Bonding: Highlighting a Potential Role for Microglia

Pair bonds represent some of the strongest attachments we form as humans. These relationships positively modulate health and well-being. Conversely, the loss of a spouse is an emotionally painful event that leads to numerous deleterious physiological effects, including increased risk for cardiac dysfunction and mental illness. Much of our understanding of the neuroendocrine basis of pair bonding has come from studies of monogamous prairie voles (Microtus ochrogaster), laboratory-amenable rodents that, unlike laboratory mice and rats, form lifelong pair bonds. Specifically, research using prairie voles has delineated a role for multiple neuromodulatory and neuroendocrine systems in the formation and maintenance of pair bonds, including the oxytocinergic, dopaminergic, and opioidergic systems. However, while these studies have contributed to our understanding of selective attachment, few studies have examined how interactions among these 3 systems may be essential for expression of complex social behaviors, such as pair bonding. Therefore, in this review, we focus on how the social neuropeptide, oxytocin, interacts with classical reward system modulators, including dopamine and endogenous opioids, during bond formation and maintenance. We argue that an understanding of these interactions has important clinical implications and is required to understand the evolution and encoding of complex social behaviors more generally. Finally, we provide a brief consideration of future directions, including a discussion of the possible roles that glia, specifically microglia, may have in modulating social behavior by acting as a functional regulator of these 3 neuromodulatory systems.

Peromyscus transcriptomics: Understanding adaptation and gene expression plasticity within and between species of deer mice

Deer mice in the genus Peromyscus occupy nearly every terrestrial habitat in North America, and have a long history as subjects of behavioral, ecological, evolutionary, and physiological study. Recent advances in transcriptomics, the study of the complete set of RNA transcripts produced by certain cell types or under certain conditions, have contributed to the development of Peromyscus as a model system. We review the recent use of transcriptomics to investigate how natural selection and gene expression plasticity contribute to the existence of deer mice in challenging environments such as highlands, deserts, and cities across North America. Transcriptomics also holds great promise for elucidating the genetic basis of mating systems and other behaviors in Peromyscus, but has to date been underutilized for developmental biology and disease studies. Future Peromyscus studies should apply robust comparative frameworks to analyze the transcriptomics of multiple populations of the same species across varying environmental conditions, as well as multiple species that vary in traits of interest.