Salivary oxytocin after play with parents predicts behavioural problems in preschool children

Infants' salivary oxytocin and positive affective reactions to people

Oxytocin is a neuropeptide positively associated with prosociality in adults. Here, we studied whether infants' salivary oxytocin can be reliably measured, is developmentally stable, and is linked to social behavior. We longitudinally collected saliva from 62 U.S. infants (44 % female, 56 % Hispanic/Latino, 24 % Black, 18 % non-Hispanic White, 11 % multiracial) at 4, 8, and 14 months of age and offline-video-coded the valence of their facial affect in response to a video of a smiling woman. We also captured infants' affective reactions in terms of excitement/joyfulness during a live, structured interaction with a singing woman in the Early Social Communication Scales at 14 months. We detected stable individual differences in infants' oxytocin levels over time (over minutes and months) and in infants' positive affect over months and across contexts (video-based and in live interactions). We detected no statistically significant changes in oxytocin levels between 4 and 8 months but found an increase from 8 to 14 months. Infants with higher oxytocin levels showed more positive facial affect to a smiling person video at 4 months; however, this association disappeared at 8 months, and reversed at 14 months (i.e., higher oxytocin was associated with less positive facial affect). Infant salivary oxytocin may be a reliable physiological measure of individual differences related to socio-emotional development.

Neural Functions of Hypothalamic Oxytocin and its Regulation

Oxytocin (OT), a nonapeptide, has a variety of functions. Despite extensive studies on OT over past decades, our understanding of its neural functions and their regulation remains incomplete. OT is mainly produced in OT neurons in the supraoptic nucleus (SON), paraventricular nucleus (PVN) and accessory nuclei between the SON and PVN. OT exerts neuromodulatory effects in the brain and spinal cord. While magnocellular OT neurons in the SON and PVN mainly innervate the pituitary and forebrain regions, and parvocellular OT neurons in the PVN innervate brainstem and spinal cord, the two sets of OT neurons have close interactions histologically and functionally. OT expression occurs at early life to promote mental and physical development, while its subsequent decrease in expression in later life stage accompanies aging and diseases. Adaptive changes in this OT system, however, take place under different conditions and upon the maturation of OT release machinery. OT can modulate social recognition and behaviors, learning and memory, emotion, reward, and other higher brain functions. OT also regulates eating and drinking, sleep and wakefulness, nociception and analgesia, sexual behavior, parturition, lactation and other instinctive behaviors. OT regulates the autonomic nervous system, and somatic and specialized senses. Notably, OT can have different modulatory effects on the same function under different conditions. Such divergence may derive from different neural connections, OT receptor gene dimorphism and methylation, and complex interactions with other hormones. In this review, brain functions of OT and their underlying neural mechanisms as well as the perspectives of their clinical usage are presented.