Oxytocin has dose-dependent developmental effects on pair-bonding and alloparental care in female prairie voles

Abstract

The present study examines the developmental consequences of neonatal exposure to oxytocin on adult social behaviors in female prairie voles (Microtus ochrogaster). Female neonates were injected within 24 h of birth with isotonic saline or one of four dosages of oxytocin (OT). As adults, females were tested in an elevated plus-maze paradigm (a measure of anxiety and exploratory behavior), and for alloparental behavior and partner preferences. At 2 mg/kg OT, females took longer to approach pups, but were the only group to form a statistically significant within-group partner preference. At 4 mg/kg OT, females retrieved pups significantly more frequently but no longer displayed a partner preference; while females treated developmentally with 8 mg/kg spent significantly more time in side-to-side contact with a male stranger than any other treatment group. OT may have broad developmental consequences, but these effects are not linear and may both increase and decrease the propensity to display behaviors such as pair-bonding.

Figure 1

Effects of early OT treatment on frequency of pup retrievals (overall ANOVA: F(4) = 3.39, p = 0.015). This includes only females that did not attack the pup. Groups which are statistically different according to post-hoc testing are marked with different letters; groups marked with the same letters are not statistically different.

Figure 2

Effects of early OT treatment on latency (in seconds) to approach within one inch of the pup (overall ANOVA: F(4) = 2.81, p = 0.034). This includes only females that did not attack the pup. Groups which are statistically different according to post-hoc testing are marked with different letters; groups marked with the same letters are not statistically different.

Figure 3

Effects of early OT treatment on preferences for a partner vs. a stranger, measured as proportion of test time spent in side-to-side contact. Proportion of test time spent in side-to-side contact with a stranger differs significantly by treatment [χ² (4) = 10.76, p = 0.029], as does the difference between time spent with the partner and time spent with the stranger [χ² (4) = 10.05, p = 0.04].