Oxytocin
Nasally administered oxytocin has been reported to reduce fear, possibly by inhibiting the amygdala (which is thought to be responsible for fear responses). Indeed, studies in rodents have shown oxytocin can efficiently inhibit fear responses by activating an inhibitory circuit within the amygdala. Some researchers have argued oxytocin has a general enhancing effect on all social emotions, since intranasal administration of oxytocin also increases envy and "Schadenfreude". Individuals who receive an intranasal dose of oxytocin identify facial expressions of disgust more quickly than individuals who do not receive oxytocin. Facial expressions of disgust are evolutionarily linked to the idea of contagion. Thus, oxytocin increases the salience of cues that imply contamination, which leads to a faster response because these cues are especially relevant for survival. In another study, after administration of oxytocin, individuals displayed an enhanced ability to recognize expressions of fear compared to the individuals who received the placebo. Oxytocin modulates fear responses by enhancing the maintenance of social memories. Rats that are genetically modified to have a surplus of oxytocin receptors display a greater fear response to a previously conditioned stressor. Oxytocin enhances the aversive social memory, leading the rat to display a greater fear response when the aversive stimulus is encountered again.
C. Sue Carter
Carter studies social bonding, male and female parental behavior, the social control of stress reactivity and the social control of reproduction, often using animal models such as the socially monogamous prairie vole. Carter’s research focuses on neuropeptide and steroid hormones, including oxytocin, vasopressin, corticotropin-releasing hormone, and estrogen. Her research program has discovered important new developmental functions for oxytocin and vasopressin, and implicated these hormones in the regulation of long-lasting neural and effects of early social experiences. She also has a long-standing concern regarding the consequences of medical manipulations for human development and parent-child interactions, including the use of “pitocin” to induce labor and consequences of breast feeding for the mother and child. Most recently she has been examining the role of oxytocin and vasopressin in mental disorders such as autism, schizophrenia, anxiety and depression. Carter is also known for research on the physiological basis of social behavior, including studies that implicated oxytocin, vasopressin and hormones of the hypothalamic-pituitary-adrenal (“stress”) axis in the traits of monogamy including pair-bond formation. She pioneered the physiological study of socially monogamous mammals, including the prairie vole. In collaboration with Lowell Getz, Carter documented the occurrence of social monogamy in prairie voles. Her studies in rodents helped to lay the foundation for the studies of behavioral and developmental effects of oxytocin and vasopressin in humans which are in progress. In collaboration with Margaret Altemus she conducted some of the first studies documenting the importance of breast-feeding in the regulation of maternal physiology.