Suchergebnisse

The main objective of the present study was to characterize sex differences in the temporal discrimination and activity level of an animal model of attention deficit disorder (ADD) using a conjunctive 120-s variable interval 16-s differential reinforcement of low rate (VIDRL) schedule of reinforcement. The results showed that the spontaneously hypertensive (SHR) male was generally hyperactive and that the SHR female was both hyperactive and had severe time discrimination problems. The latter caused relatively fewer reinforcers to be delivered. However, even when a reinforcer was delivered, the SHR female frequently failed to collect it. When the SHR females were in diestrus, their behavior became even less efficient. The present findings with the animal model seem to be in general agreement with the behavior of ADD children when a DRL schedule is used. Most of our results were explained as due to impulsiveness, which is more pronounced in the SHR female than in the male. In addition, the SHR female had attention problems. The present study further supports the usefulness of the SHR as animal model of ADD.

Abstract We explore the neurobiological bases of attention deficit hyperactivity disorder (ADHD) from the viewpoint of the neurochemistry and psychopharmacology of the catecholamine‐based behavioural systems. The contributions of dopamine (DA) and noradrenaline (NA) neurotransmission to the motor and cognitive symptoms of ADHD (e.g. hyperactivity, variable and impulsive responses) are studied in rodent and primate models. These models represent elements of the behavioural units observed in subjects with ADHD clinically, or in laboratory settings (e.g. locomotion, changed sensitivity/responsivity to novelty/reinforcement and measures of executive processing). In particular, the models selected emphasize traits that are strongly influenced by mesocorticolimbic DA in the spontaneously hypertensive (SHR) and the Naples high excitability (NHE) rat lines. In this context, the mode of action of methylphenidate treatment is discussed. We also describe current views on the altered control by mesolimbic catecholamines of appropriate and inappropriate goal‐directed behaviour, and the tolerance or intolerance of delayed reinforcement in ADHD children and animal models. Recent insights into the previously underestimated role of the NA system in the control of mesocortical DA function, and the frontal role in processing information are elaborated.