Behavioural and pharmacological relevance of stroke-prone spontaneously hypertensive rats as an animal model of a developmental disorder.

The present study evaluates juvenile stroke-prone spontaneously hypertensive rats (SHRSP) as an animal model of a developmental disorder, which is diagnosed according to hyperactivity-impulsivity and/or inattention. To characterize behavioural alterations, we studied motor activity, as well as emotional and cognitive behaviours in juvenile SHRSP, with and without methylphenidate, a psychostimulant. Ambulatory and rearing activities in the open-field environment were significantly higher in SHRSP than in Wistar-Kyoto rats (WKY). In the elevated plus maze task, the entries into open arms, as an index of impulsivity, were significantly increased in SHRSP. In the Y-maze task, spontaneous alternation behaviour, as an index of attention, was significantly lowered in the male SHRSP, but not in the female SHRSP, indicating that spontaneous alternation deficit is gender specific. Methylphenidate (0.01-1 mg/kg, i.p.) significantly attenuated locomotor hyperactivity at low doses and dose-dependently improved the spontaneous alternation deficit in SHRSP. Our findings reveal that juvenile SHRSP manifest problematic behaviours resembling a developmental disorder, attention-deficit/hyperactivity disorder (ADHD), namely hyperactivity-impulsivity and/or inattention. Methylphenidate alleviated the behavioural symptoms of hyperactivity and inattention. We propose that juvenile SHRSP are an appropriate animal model of a developmental disorder resembling ADHD, from behavioural and pharmacological perspectives.