Sex differences and developmental effects of manipulations of oxytocin on alloparenting and anxiety in prairie voles.

In adult animals, peptide hormones, including oxytocin and arginine vasopressin, have been implicated in both parental behavior and the modulation of anxiety. The purpose of this study was to examine the consequences of developmental manipulations of oxytocin for the later expression of alloparental behavior as well as behavioral responses to a novel environment, the elevated plus maze (EPM). Prairie voles (Microtus ochrogaster), a cooperatively breeding species, were selected for this study. On neonatal Day 1, pups received an ip injection of oxytocin or oxytocin antagonist, or were controls, receiving either saline or handling only. At 21 and approximately 60 days of age, each animal was tested for parental care toward novel stimulus pups. At approximately 67 days, an EPM test was administered. Control females at 60 days of age were more likely to attack pups and spent less time in the open arm of the EPM, both of which might reflect higher levels of anxiety in females than males. In males, neonatal treatment with oxytocin antagonist was associated with reductions in parental care, especially during the initial exposure to pups on Day 21. Female behavior was not significantly changed as a function of neonatal treatments. Findings to date implicate vasopressin in the behavioral changes in males, that in later life followed a single exposure to an oxytocin antagonist, and suggest caution in the clinical use of agents such as Atosiban, which may have the potential to influence infant development. Copyright 2004 Wiley Periodicals, Inc. Dev Psychobiol 44: 123-131, 2004.