Aversive motivation and the maintenance of monogamous pair bonding.

Social bonds are important for human health and well-being, and a crucial component of these bonds is the ability to maintain a bond once it has been formed. Importantly, although bond maintenance is required for social attachments, very little is known about the neural mechanisms that mediate this behavior. Recently, laboratory studies utilizing the socially monogamous prairie vole (an excellent animal model for the neurobiology of selective social attachment), have allowed the neural correlates of selective social attachment to begin to unfold. These studies have identified that the activation of both motivational and hedonic processing systems, which mediate other natural rewards, is also important for mediating social behaviors that are characteristic of an established pair bond. These social behaviors include appetitive and positive social interactions with a potential mating partner in sexually naïve prairie voles, the avoidance of novel conspecifics (and sometimes aggressive rejection) that characterizes the established pair bond and, finally, an aversion towards partner separation. The following review will discuss how a balance between opposing endogenous opioid systems - positive (mu-opiod receptors) and aversive (kappa-opioid receptors) - provide essential hedonic signaling that guides socially motivated behaviors.