Previous studies have demonstrated that central administration of vasopressin but not oxytocin facilitates pair bonding in the monogamous male prairie vole. This study tested vasopressin and oxytocin in the formation of the female vole's preference for a particular male partner. Initial studies showed that in monogamous female prairie voles (but not in nonmonogamous congeners), mating was followed by a partner preference that endured for at least 2 weeks. Nonmating prairie vole females developed a partner preference following oxytocin infusions, but not after vasopressin or cerebrospinal fluid infusions. Females given a selective oxytocin antagonist showed normal mating behavior, yet failed to develop a partner preference. The vasopressin antagonist failed to block partner preference formation in mated females. These results suggest that oxytocin, released with mating, may be critical to formation of a partner preference in the female prairie vole; this contrasts to vasopressin, which appears to be more important for pair bonding in the male of this species.

No abstract

The genus Microtus includes several closely related species of voles with diverse patterns of social organization. Comparative studies of these species have previously tested hypotheses related to the evolution of monogamy and affiliation. In earlier studies, monogamous voles have been reported to differ from closely related nonmonogamous voles in the neural distribution of oxytocin and vasopressin receptors. These receptors have also been implicated in the behavioral differences relevant to monogamy, as oxytocin and vasopressin influence pair-bond formation in the monogamous species. In the current study, two monogamous and two nonmonogamous vole species were compared for the distribution of oxytocin and vasopressin immunoreactivity. Contrary to our predictions, gender dimorphisms in vasopressin immunoreactivity were as evident in the monogamous as in the nonmonogamous species. Also, species differences in oxytocin and vasopressin staining were subtle relative to the profound species differences previously reported for receptor binding. These results are consistent with the hypothesis that neuroendocrine systems may evolve by changes in receptor distribution rather than by restructuring the presynaptic pathway.

The genus Microtus includes several closely related species of voles with diverse patterns of social organization. Comparative studies of these species have previously tested hypotheses related to the evolution of monogamy and affiliation. In earlier studies, monogamous voles have been reported to differ from closely related nonmonogamous voles in the neural distribution of oxytocin and vasopressin receptors. These receptors have also been implicated in the behavioral differences relevant to monogamy, as oxytocin and vasopressin influence pair-bond formation in the monogamous species. In the current study, two monogamous and two nonmonogamous vole species were compared for the distribution of oxytocin and vasopressin immunoreactivity. Contrary to our predictions, gender dimorphisms in vasopressin immunoreactivity were as evident in the monogamous as in the nonmonogamous species. Also, species differences in oxytocin and vasopressin staining were subtle relative to the profound species differences previously reported for receptor binding. These results are consistent with the hypothesis that neuroendocrine systems may evolve by changes in receptor distribution rather than by restructuring the presynaptic pathway.

No abstract