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NATIONAL INSTITUTE OF MENTAL HEALTH STUDIES PAIR BONDING

 /ADVANCE/ WASHINGTON, Oct. 6 /PRNewswire/ -- Pair bonding in a monogamous rodent species has been traced to the action of a single brain hormone. A scientific team led by Thomas Insel, M.D., of the National Institute of Mental Health (NIMH) has discovered in male prairie voles that arginine-vasopressin (AVP) is the "necessary and sufficient" ingredient for selection of a lifelong mate and for guarding her from intruders.
 This furry, mouselike species, native to the American Midwest, shows a genetically programmed pattern of monogamous social behavior after mating: the pair cuddles a lot, shares a nest and parenting chores and the male becomes aggressive toward strangers in defense of the family.
 To find out the neural basis of such familial behavior, Insel and colleagues examined the brains of monogamous and polygamous vole species. They uncovered conspicuous differences in the circuitry for two brain hormones, AVP and oxytocin, that appear to be the basis for the species' divergent lifestyles.
 In the male prairie vole, Insel and colleagues observed that both protective aggressiveness toward strangers and a preference for the mate over a strange female emerged within 24 hours after mating. Mating increases AVP activity. When the investigators blocked AVP with an antagonist drug, mating failed to trigger protective aggressiveness or a partner preference; the males spent as much time with a strange female as with the mate. Yet, giving an infusion of AVP -- without mating -- produced the same two changes in social behavior as mating.
 Neither measure of pair bonding was affected by oxytocin or an oxytocin blocker. Nor were the changes seen after mating in a non- monogamous vole species, which does not form pair bonds and has a different pattern of brain AVP circuitry.
 Studies by other investigators in male prairie voles have shown that AVP also induces parenting behavior, a third major measure of monogamous bonding. Mating fails to stir aggression in the female, but facilitates partner preference; oxytocin induces mate preference in the absence of mating in the female.
 While AVP and oxytocin are present in all mammals and have even been implicated in human sexual behavior, Insel cautions against simplistic interpretations of the new findings.
 "Pair bonding is a complex series of processes -- involving recognition, memory, defense, affiliation, motivation and separation reactions -- which cannot be explained by a single peptide," noted Insel, who is a psychiatrist as well as a neuroscientist. "In the vole, it is not yet clear which of these processes are affected by AVP. In humans, there is as yet no information on whether any of these processes are affected by either vasopressin or oxytocin."
 Neither AVP nor oxytocin can currently be administered in a form capable of crossing the blood-brain barrier. However, Insel speculates that knowledge about these systems could lead to the engineering of agents that may prove useful in treating disorders of social bonding, such as infantile autism and certain forms of schizophrenia.
 Collaborating on the project with Insel were: James Winslow, Ph.D., and Carroll Harbaugh of NIMH, and Sue Carter, Ph.D., and Nick Hastings of the University of Maryland, College Park. A report on their research, "Central vasopressin mediates pair bonding in the monogamous prairie vole," is published in the Oct. 7 issue of Nature.
 -0- 10/6/93/1830
 /CONTACT: Jules Asher, 301-443-3677, or Marilyn Weeks, 301-443-4536, both of the National Institute of Mental Health/


CO: National Institute of Mental Health ST: District of Columbia IN: MTC SU:

DC-MH -- DC012 -- 9311 10/06/93 11:48 EDT
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Date:Oct 6, 1993
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