Brain Oxytocin Mediates Beneficial Consequences of Close Social Interactions: FromMaternal Love and Sex

There is growing interest directed toward understanding positive emotions, and maternal and romantic love are among the most desired and positive social experiences encountered. It is only now that we are beginning to understand not only their neurobiological and neurochemical regulation but also their beneficial health consequences. For example, around parturition, profound adaptations of the maternal brain take place with significant behavioural consequences that ensure the healthy development of the child, or the offspring, including nutrition, protection and maternal emotional care. There is an activation of several neuroendocrine systems, including oxytocin and prolactin, that play important roles as classical hormones in the regulation of parturition, lactogenesis and milk ejection, respectively. Importantly, as signalling molecules of the brain, they were shown to be important promoters of maternal behaviour. Moreover, oxytocin released within the rat brain is correlated with the protection of the offspring, i.e., with the display of maternal aggression. Thus, oxytocin and prolactin are important for meeting the physiological demands of the offspring, but also to satisfy their emotional demands, including protection and close affiliation with the mother. In turn, the maternal brain profits from these adaptations: oxytocin and prolactin exert anxiolytic effects at various brain sites and have been shown to reduce stress responsiveness at neuronal, neuroendocrine and behavioural levels. As a consequence, increased calmness, reduced anxiety levels and blunted hypothalamopituitary-adrenal axis and sympathetic responses to numerous stressors have been described in pregnancy and/or lactation, both in human and animal studies. These complex brain adaptations are clearly beneficial for themother. However, they are vulnerable to stressful life experiences andmaladaptations, e.g., lack of adaptive activation of the brain oxytocin and prolactin systems may result in postpartummood disorders with negative consequences for both maternal health and child development. Is there a comparable physiological and behavioural situation in males? There is scientific and anecdotal evidence for sedation and calmness after sexual activity. Oxytocin is released within the hypothalamus during mating, where it is crucially involved in the regulation of male sexual behaviour. Evidence will be provided that activation of brain oxytocin, as seen during sexual activity, also mediates beneficial effects in males.