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12:01 AM EDT/Friday, April 17, 2009
Contact: Donna Krupa
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Office: (301) 634-7209
Cell: (703) 967-2751
dkrupa@the-aps.org
Stress Of
Isolation Early In Life Linked To Enhanced
Juvenile Response To Cocaine
New study finds males more susceptible to this effect than females
in an animal model
NEW ORLEANS—Drug
addiction affects millions of people around the world, causing numerous
problems ranging from emotional and psychological difficulties to physical
and health issues. Initial drug use can be motivated by curiosity or peer
pressure, but in some animals, such as rats, it can also be the result of a
stressful early life event, such as social isolation. A new study examines
the impact of social isolation on the animal’s response to cocaine.
The study, Social
Isolation During Perinatal Development Alters the Behavioral Response to
Cocaine in Juvenile Rats, was conducted by Natasha Lugo-Escobar, Nicole
Carreras and Annabell C. Segarra, University of Puerto Rico, School of
Medicine, Rio Piedras, PR. The team will present its findings at the 122nd
Annual Meeting of the American Physiological Society (APS;
www.the-aps.org/press), which is part of the Experimental Biology 2009
scientific conference. The meeting will be held April 18-22, 2009 in New
Orleans.
The Study
Drugs of abuse act on the
reward centers of the brain. These areas are normally involved in mediating
pleasure, and also regulate the psycho-stimulant effects of drugs such as
cocaine. Stress is known to enhance drug seeking behavior, as well as the
psychostimulant effects of cocaine. Since rats are social animals, isolation
was used as a stressor to explore the association between stress during
development and susceptibility to the psychostimulant effects of drugs of
abuse, such as cocaine.
Rats were stressed: (1) as fetuses (by housing the
pregnant mother alone), (2) as neonates (by isolating newborn rats for 1 hr
daily during the first 9 days of life) or as adolescents (by housing each
rat separately during days 21-35). Two additional groups: (4) isolated as
fetuses, neonates and adolescents and (5) controls - not isolated during any
developmental period, comprised the 5 groups studied. When rats reached 21
days of age, they were weaned from their mothers and tested for the
psychostimulant response to cocaine as well as for the development of
sensitization, a phenomenon characterized by an increase response to the
same amount of a drug over time. For 5 days, half of the rats from all
groups were injected with saline and the other half with cocaine (15
mg/kg). This was followed by a 7 day drug free period and an additional
cocaine injection on day 13. Locomotor activity was measured on days 1, 5
and 13 immediately after injection.
Results
The researchers found that:
v
SEQ CHAPTER \h \r 1Rats that were
isolated during all three developmental periods, showed a higher locomotor
response to cocaine than control rats.
v
The study indicates that the developmental period most
susceptible to isolation stress, particularly in males, is the neonatal
period, since males isolated as neonates show an increase in the locomotor,
and sensitized response to cocaine, compared to male control and to female
rats.
Conclusions
This study suggests that
isolation during early development alters the brain sensitivity to cocaine,
such that when the animal reaches adolescence and is exposed to cocaine, it
is more sensitive to the psychostimulant effects of the drug.
These studies contribute to understanding the
mechanisms that may lead to greater abuse of drugs during adolescence.
Additional studies are
planned.
*********
Physiology
is the study of how molecules, cells, tissues and organs function to create
health or disease. The American Physiological Society (APS;
www.The-APS.org/press) has been an integral part of this discovery
process since it was established in 1887.
NOTE TO EDITORS: The APS annual meeting is part
of the Experimental Biology 2009 (EB ’09) gathering and will be held April
18-22, 2009 at the New Orleans Convention Center. To schedule an interview
with a member of the research team, please contact Donna Krupa
at 301.634.7209 (office), 703.967.2751 (cell) or
DKrupa@the-APS.org.
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