Cellular mechanisms of social attachment

Pharmacological studies in prairie voles have suggested that the neuropepti des oxytocin and vasopressin play important roles in behaviors associated w ith monogamy, including affiliation, paternal care, and pair bonding. Our l aboratory has investigated the cellular and neuroendocrine mechanisms by wh ich these peptides influence affiliative behavior and social attachment in prairie voles. Monogamous prairie voles have a higher density of oxytocin r eceptors in the nucleus accumbens than do nonmonogamous vole species; block ade of these receptors by site-specific injection of antagonist in the fema le prairie vole prevents partner preference formation. Prairie voles also h ave a higher density of vasopressin receptors in the ventral pallidal area, which is the major output of the nucleus accumbens, than montane voles. Bo th the nucleus accumbens and ventral pallidum are key relay nuclei in the b rain circuits implicated in reward, such as the mesolimbic dopamine and opi oid systems. Therefore, we hypothesize that oxytocin and vasopressin may be facilitating affiliation and social attachment in monogamous species by mo dulating these reward pathways. (C) 2001 Academic Press.