Effects of atomoxetine and methylphenidate on performance of a lateralized reaction time task in rats.
BACKGROUND
The ability to detect unpredictable cues can involve stimulus-elicited orienting of attention (bottom-up processing); however, in many settings, target onset is partially predictable, meaning that subjects can benefit from the rule-guided, endogenous control of attention (top-down processing). Noradrenaline has been implicated in attention per se, but it is not clear whether it differentially participates in these two dimensions of attentional function.


OBJECTIVE
We sought to examine the effects of selective or nonselective inhibitors of noradrenaline reuptake on different modes of attentional performance in rats.


METHODS
Adult male Long-Evans rats were trained to perform a lateralized reaction time task where a variable-duration preparatory period preceded delivery of a visual target stimulus. Atomoxetine (1 mg/kg, i.p.) or methylphenidate (0.32 mg/kg, i.p.) were administered before sessions in which the preparatory period was systematically varied.


RESULTS
When the preparatory time was brief (0.2 s), response times were significantly longer than when the preparatory time was long (1.0 s), suggesting that rats were able to orient their attention before target onset when the longer period was imposed. Atomoxetine differentially modulated performance in these two conditions, improving response accuracy when a long preparatory period was imposed but impairing accuracy when the preparatory time was made brief. Methylphenidate did not differentially affect responding under the two conditions.


CONCLUSIONS
These data suggest that selective inhibition of the noradrenaline transporter may specifically benefit attentional performance of tasks that permit the controlled recruitment of attention, rather than during tests of pure stimulus-driven attention.
Department of Psychology, University of California, Los Angeles, P.O. Box 951563, Los Angeles, CA 90095-1563, USA. jentsch@psych.ucla.edu
J David
JD
Jentsch
Shawn M
SM
Aarde
Emanuele
E
Seu
D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology*; D000818:Animals; D000069445:Atomoxetine Hydrochloride; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003216:Conditioning, Operant / Q000187:drug effects; D004192:Discrimination, Psychological / Q000187:drug effects; D007839:Functional Laterality / Q000187:drug effects; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D011437:Propylamines / Q000494:pharmacology*; D011597:Psychomotor Performance / Q000187:drug effects*; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time / Q000187:drug effects*; D012691:Serial Learning / Q000187:drug effects
D018759:Adrenergic Uptake Inhibitors; D000697:Central Nervous System Stimulants; D011437:Propylamines; D008774:Methylphenidate; D000069445:Atomoxetine Hydrochloride