The reward mechanism involved in addiction appears to regulate
lifelong social or pair bonds between monogamous mating animals,
according to a Center for Behavioral Neuroscience (CBN) study of
prairie voles published in the Jan. 19 edition of the Journal of
finding could have implications for understanding the basis of
romantic love and disorders of the ability to form social attachments,
such as autism and schizophrenia.
research funded by the National Institute of Mental Health, Larry
Young, associate professor of psychiatry and behavioral sciences
and an affiliate scientist at Yerkes National Primate Research
Center; graduate student Miranda Lim; and Anne Murphy, associate
professor of biology at Georgia State University, examined the
distribution of two brain receptors in the ventral forebrain of
monogamous prairie voles that have been previously tied to pair
bond formation: oxytocin (OTR) and vasopressin V1a receptor (V1aR).
receptor audiographic techniques, the scientists found that these
receptors are confined to two of the brain's reward centers, the
nucleus accumbens and the ventral pallidum. V1aR receptors, thought
to be activated in the male vole brain during pair bond formation,
were confined largely to the ventral pallidum. OTR receptors, which
play a crucial role in pair bond formation in females, were found
mainly in the nucleus accumbens.
V1aR and OTR receptors did not overlap between the two brain regions
and were equally distributed in the brains of male and female voles.
Young said the findings, coupled with the proximity of the nucleus
accumbens and ventral pallidum--two regions with heavily interconnected
structures--suggest a common neural circuit in male and female voles
regulates pair bond formation.
studies have found the dopamine system of the nucleus accumbens
produces the rewarding and sometimes addictive effects of sex,
food and drugs of abuse. Young believes the same reward pathways
are likely stimulated during and following pair bond formation.
the process of pair bond formation results from the activity of
two different neurochemicals in separate regions of the ventral
forebrain in male and female vole brains," Young said, "the OTR
and V1aR systems appear to activate two separate nodes of the same
reward pathway to form and reinforce pair bonds."
another finding, the CBN researchers determined that OTR and V1aR
are located near the nerve fibers that release oxytocin and vasopressin.
Lim speculated that their proximity likely facilitates pair bond
formation during mating.
studies currently under way continue to examine other components
of the neural circuit involved in pair bond formation. The monogamous
prairie vole, which forms lifelong pair bonds, provides an ideal
animal model for studying the neural basis of social attachment.
In previous studies, CBN scientists have determined:
· The genes for vasopressin and oxytocin are critical for the
proper processing of social information.
· A lack of genes for vasopressin and oxytocin receptors results
in a deficit in social recognition and altered anxiety in mice.
· Vasopressin and oxytocin play key roles in the formation of
social attachments between animals. Increasing the amount of vasopressin
receptors in the brain using gene transfer techniques can increase
pair-bonding behavior in monogamous male prairie voles.
CBN, a National Science Foundation Science and Technology Center,
is a research and education consortium consisting of Emory, Georgia
State, Georgia Tech and the five schools comprising the Atlanta
University Center (Clark Atlanta, Morehouse, Morehouse School of
Medicine, Morris Brown and Spelman). CBN researchers study four
aspects of social behavior: fear, aggression, affiliation and reproduction.