[Abstract Title]. - Society for Neuroscience

Poster
291. Animal Cognition and Behavior: Learning and Memory: Pharmacology II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 291.22/SS5
Topic: F.02.j. Learning and memory: Pharmacology
Support: SENACYT Grant FID06-001
Title: Long-term exposure to clinically relevant doses of oral methylphenidate has enduring
effects on emotional behaviors in rats
Authors: J. A. BETHANCOURT 1,2 , Z. Z. CAMARENA 1,2 , C. B. SALAZAR 3 , G. C.
QUINTERO 1 , *G. B. BRITTON 1 ;
1 Cognición, Cerebro y Conducta, INDICASAT, Panama, Panama; 2 Facultad de Psicología, Univ.
de Panamá, Panamá, Panama; 3 Facultad de Psicología, Univ. Católica Santa María la Antigua,
Panamá, Panama
Abstract: Methylphenidate (MPH) is the most commonly prescribed psychostimulant used in
the treatment of symptoms associated with attention-deficit/hyperactivity disorder (ADHD) in
children, adolescents and adults. Despite its widespread use, general safety and effectiveness, a
rising concern involves its potential to modify neural developmental processes that take place
during pre- and peri-adolescence and to produce enduring changes in neural structure and
function. Behavioral studies have shown that rats treated with MPH during early developmental
periods exhibit cognitive and emotional deficits in adulthood, presumably due to long-lasting
effects of MPH on maturing dopaminergic systems. Whether the therapeutic benefits of MPH
outweigh its effects on neurobehavioral processes remains unknown. Because a growing
proportion of adolescents continue MPH use into young adulthood, the present study examined
the long-term effects of MPH administration from early developmental periods through
adulthood on emotional and cognitive behaviors, and spontaneous locomotion and exploration.
Peri-adolescent Wistar rats (beginning at post-natal day 28) were treated twice daily with MPH
(2, 3 or 5 mg/kg) for seven weeks using an oral administration procedure that parallels clinical
practice (weekdays only). Two weeks following the last drug treatment, animals were tested over
a five-week period on a battery of procedures including the open field, novel object recognition,
light-dark transition, elevated plus maze, and fear conditioning paradigms. We found that rats
exposed to 3 or 5 mg/kg exhibited increases in anxiety-related behaviors measured in the open
field, light-dark transition, and fear conditioning tests, but no deficits were observed in
locomotion or exploration, or in the object recognition test at short or long retention intervals.
These results are a first demonstration that MPH administration from juvenile periods through
adulthood at clinically relevant doses has enduring effects on emotional responding without