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Peptide Shown To Regulate
Social Behavior Has Positive Impact On
Cardiac Response Following Social Isolation
WASHINGTON – A team of researchers investigating
the effects of oxytocin, a peptide produced by the brain that regulates
social behavior, has found that it can prevent detrimental cardiac responses
in adult female animals exposed to social isolation. The findings may
provide further insight into how these mechanisms affect humans.
The study was conducted by Angela J. Grippo, C. Sue
Carter and Stephen W. Porges, all with the Department of Psychiatry and
Brain-Body Center at University of Illinois at Chicago and is titled
Chronic Oxytocin Treatment Mediates Heart Rate Responses Following Social
Isolation. Dr. Grippo is presenting the team’s findings at the 120th
annual meeting of the American Physiological Society (APS;
www.The-APS.org), being held as part of the Experimental Biology (EB
’07) conference. More than 12,000 scientific researchers will attend the
gathering being held April 28-May 2, 2007 at the Washington, DC Convention
Center.
Background
The social environment
plays an important role in regulating both behavior and cardiovascular
function in humans. Negative social interactions, such as loneliness or
social isolation, may increase the risk of developing depression and anxiety
as well as heart disease.
Prairie voles (ochrogaster)
are small rodents that demonstrate features of social interactions similar
to humans and therefore provide a useful animal model for investigating how
the social environment influences behavior and cardiac function. Earlier
studies by this research team showed that when prairie voles were isolated
from their families, they displayed behaviors similar to depression and
cardiovascular changes indicating a possible increased risk of heart disease
(including elevated resting heart rate, reduced heart rate variability, and
reduced parasympathetic regulation of the heart).
This study examines
whether oxytocin plays a role in the heart’s detrimental responses to social
isolation.
The Study: Summary of Methodology
Adult female prairie voles
were placed under anesthesia and implanted with wireless, radio frequency
transmitters. The animals were subsequently exposed to either social
isolation or pairing with a female sibling (control conditions) for four
weeks. They were treated with oxytocin or saline (control solution) daily
for 14 days during the third and fourth week of the four-week isolation
period. Electrocardiographic parameters (heart rate and heart rhythms) were
recorded using the radio frequency transmitter. Following the period of
isolation or pairing, all animals were exposed to a mild social stressor (a
five minute social interaction test with an unfamiliar animal).
Results
The researchers found
that:
 the
animals exposed to isolation had an increase in heart rate and a reduction
in heart rate variability. The administration of oxytocin significantly
improved both heart rate and heart rate variability;
for the
animals exposed to isolation, oxytocin significantly reduced the heart rate
response following the five-minute resident intruder social interaction
test;
for the
isolated animals, oxytocin significantly improved parasympathetic regulation
of the heart; and
for the
paired prairie voles (control group) oxytocin did not alter the cardiac
responses.
Conclusions
These findings suggest that oxytocin can prevent
damaging cardiac changes in adult female prairie voles exposed to social
isolation. While there are limitations to the study, including the lack of
spontaneous puberty and estrous cycles in female prairie voles (unlike their
human counterpart), the results serve as a springboard into better
understanding the mechanisms that underlie the relations between social
behavior and cardiac function in humans.
***
The
American Physiological Society (APS) has been an integral part of the
scientific discovery process since it was established in 1887. Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease.
# # #
NOTE TO EDITORS: The APS annual meeting is part
of the Experimental Biology 2007 (EB ’07) gathering and will be held April
28-May 2, 2007 at the Washington, DC Convention Center. To schedule an
interview with Dr. Grippo, please contact Donna Krupa.
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