Background
Attention-deficit/hyperactivity disorder is a heterogeneous disorder that is classified
into three subtypes in which the main symptoms, inattention, hyperactivity, and impulsivity,
are expressed with various degrees of severity. The nature of the biological dysfunction
sustaining each subtype (common or distinct) is unknown, and animal models encompassing
different subtypes are needed.
Methods
A cluster analysis separated subgroups of rats on the basis of similarities in both
impulsivity and attentional scores in the five-choice serial reaction time task. These
subgroups were characterized behaviorally and were compared for several aspects of
spontaneous hyperactivity in different environmental contexts. The dose effects of
two agents used clinically (methylphenidate and atomoxetine) were tested on attention
and impulsivity.
Results
Four distinct subgroups were demonstrated: efficient, middle, inattentive, and inattentive–impulsive.
Hyperactivity expressed in a cage, characterized the last subgroup. Subgroups were
differentially sensitive to environmental and pharmacologic challenges. Methylphenidate
increased impulsivity mainly in the combined subgroup, whereas atomoxetine decreased
impulsivity, neither with any effect on the efficient subgroup and on accuracy.
Conclusions
This new approach is the first to demonstrate behavioral subtypes in rats that parallel
those observed in human beings and is a promising tool to clarify the biological bases
of these behavioral subtypes and to explain therapeutic effects.
Key Words
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Article info
Publication history
Published online: October 20, 2006
Accepted:
June 14,
2006
Received in revised form:
March 23,
2006
Received:
November 18,
2005
Identification
Copyright
© 2007 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.