Methylphenidate reduces impulsive behaviour in juvenile Wistar rats, but not in adult Wistar, SHR and WKY rats.
BACKGROUND
Impulsivity is a core symptom of attention deficit/hyperactivity disorder (ADHD). The spontaneously hypertensive rats (SHR) is a strain commonly used as an animal model of ADHD. However, there is no clear evidence that psychostimulants, which are used for treatment of ADHD, reduce impulsivity in SHR. Because ADHD mainly affects children, it may be relevant to study psychostimulants on juvenile animals.


OBJECTIVE
Using tolerance to delay of reward as index of impulsivity, the effects of methylphenidate were assessed in adult SHR, Wistar Kyoto (WKY) and Wistar rats and in juvenile Wistar rats.


METHODS
Animals were trained in a T-maze to choose between a small-but-immediate and a large-but-delayed reward. Adult SHR, WKY and Wistar rats were compared for their ability to tolerate a 15-s delay. The effect of methylphenidate on the tolerance to a 30-s delay was studied in adult rats of the three strains and in juvenile (4.5 to 6.5-week-old) Wistar rats.


RESULTS
In adult rats, the waiting ability was lower in SHR than in control strains. Waiting ability was improved by methylphenidate (3 and 5 mg/kg) in juveniles, but not by methylphenidate (3 mg/kg) in adults.


CONCLUSIONS
These data support the idea that SHR are more impulsive than control strains. However, at the dose studied, methylphenidate fails to improve tolerance to delay in adult rats whatever the strain used. The reduction of impulsivity induced by methylphenidate in juvenile Wistar rats indicates that juvenile animals may be suitable for testing the therapeutic potential of drugs intended to the treatment of ADHD in children.
Bizot
Jean-Charles
JC
Key-Obs SA, Parc Technologique de La Source, 3 allée du Titane, 45100, Orleans, France. jeancharles.bizot@key-obs.com
Chenault
Nicolas
N
Houzé
Bérengère
B
Herpin
Alexandre
A
David
Sabrina
S
Pothion
Stéphanie
S
Trovero
Fabrice
F
D000367:Age Factors; D000818:Animals; D001289:Attention Deficit Disorder with Hyperactivity / Q000188:drug therapy / Q000523:psychology; D001522:Behavior, Animal / Q000187:drug effects; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003216:Conditioning, Operant; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D007175:Impulsive Behavior / Q000188:drug therapy* / Q000523:psychology; D008297:Male; D018782:Maze Learning; D008774:Methylphenidate / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017208:Rats, Wistar; D013045:Species Specificity
D000697:Central Nervous System Stimulants; D008774:Methylphenidate