SEX-DIFFERENCES IN OPERANT DISCRIMINATION BEHAVIOR IN AN ANIMAL-MODELOF ATTENTION-DEFICIT HYPERACTIVITY DISORDER

The present study was aimed at determining whether the behaviour of th e spontaneously hypertensive rat (SHR), an animal model of attention-d eficit hyperactivity disorder (ADHD), showed sex differences parallel to those seen in ADHD children. The experimental protocol contained an operant discrimination task, a two-component multiple (mult) 2-min fi xed interval (FI) 5-min extinction (EXT) schedule of water reinforceme nt, a reliable behavioural paradigm for testing activity levels, discr imination behaviour and impulsiveness. The results indicated that both male and female SHRs show some of the most important behavioural trai ts of ADHD. Both were hyperactive and showed discrimination problems i n terms of a behavioural extinction deficit towards the end of the EXT component. Still their behaviour differed markedly, which was probabl y due to quite different underlying mechanisms. The behavioural charac teristics of the female SHRs may be compatible with an attention-defic it interpretation, whereas the behavioural characteristics of the male SHRs may be due to a shorter than normal delay-of-reinforcement gradi ent. The present study strengthens the position of SHR as an animal mo del of ADHD for future studies that may elucidate details in the under lying neurobiological deficits and for testing various treatment strat egies. (C) 1998 Elsevier Science B.V. All rights reserved.