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184 EFFECTS OF EARLY MALTREATMENT AND STRESSThe effects of neonatal manipulations of OT on the AVP V1a receptor weresexually dimorphic; females treated with OT (rather than OTA) showed decreasedV1a receptor binding in the ventral pallidum and LS. Consistent with our behavioralfindings, the low doses used here did not disrupt pair bonding, OT receptors,or dopamine (D2) receptors (Bales et al., 2004c). The capacity of neonatalOT or OTA to produce regionally selective and sexually dimorphic effects on theAVP (V1a subtype) receptor system is consistent with several of the behavioraleffects seen after peptide manipulations. These findings support the importanceof continuing to explore the developmental actions of these and related peptidesin both sexes and on specific neural targets.Because the adolescent period is typically marked by increases in sexual dimorphism,it seems likely that neuropeptide effects also might become more apparentduring adolescence. However, in voles the dramatic changes normallyassociated with puberty are modulated by social experience (Carter et al., 1995).Especially in female prairie voles, puberty can be delayed in animals that remainin the family and stimulated by exposure to a novel member of the opposite sex.This feature of vole reproductive biology has advantages in studies in which it isdesirable to minimize the role of gonadal steroids. In addition, it has allowed thefunctions of neuropeptides such as OT and AVP to be understood somewhat independentlyof steroid hormones. However, for this same reason, studies of pubertalchanges in prairie voles may not be identical to those in mammals that exhibita spontaneous puberty.Does Neonatal “Handling” Have Parallels to ThoseObserved Following Neuropeptide Manipulations?In ongoing studies, we have observed striking differences in behavior due to apparentlyminor manipulations of prairie voles in the first few weeks of life. Thesefindings, described below, are consistent with an earlier literature in rats, sometimescalled “handling” paradigms, in which animals were either left undisturbed(no handling) during the first week or more of life or experienced brief (15-minute)or longer (3-hour) separations from the mother. Brief separations can be apparentlyadvantageous, possibly through the induction of subsequent increases inmaternal stimulation. Longer separations typically resulted in dysregulation of thehypothalamic-pituitary adrenal (HPA) axis and may produce animals that areparticularly reactive to stressors experienced in later life (Levine, 2001; Levine,2002; Plotsky, Sanchez, & Levine, 2001). As mentioned above, research in ratsdoes not address the effects of early “handling” on selective social behaviors orsocial bonds. The research in rats and coincidental observations of our own in volesled us to explore the effects of early handling/manipulations on the features ofsocial monogamy including pair bonding, as well as alloparenting. This work arosefrom an initial observation that some of the characteristics of prairie voles, generallyviewed as species-typical traits, became less apparent in animals in which