Comparison of SHR, WKY and Wistar rats in different behavioural animal models: effect of dopamine D1 and alpha2 agonists

Spontaneously hypertensive rats (SHR) and its counterpart, the Wistar-Kyoto rats (WKY), are probably the most often used animal model of ADHD. However, SHR as model of ADHD have also been criticised partly because of not differing to outbred rat strains. In the present study, adolescent SHR, WKY and Wistar rats from Charles River were tested in open-field, elevated plus maze and novel object recognition and on gastrointestinal transport to more intensively evaluate the strain characteristics. Non-habituated SHR and Wistar rats were more active than WKY rats but contrary to Wistar rats SHR stay hyperactive in a familiar environment. SHR were more sensitive to the alpha2-adrenoceptor agonist guanfacine and the dopamine D1 agonist A-68930 than WKY and Wistar rats, whereas amphetamine, the D1/D5 agonist ABT431 and the D2 agonist quinpirole, similarly affected open-field activity in all strains. In the elevated plus maze, SHR and Wistar rats showed less anxiety-related behaviour than WKY rats. Guanfacine and amphetamine induced an anxiolytic-like activity in SHR but not in WKY and Wistar rats. SHR showed the highest long-term memory in the novel object recognition. Gastrointestinal transport was similar and comparably affected by guanfacine in all rat strains. The present study shows clear differences in the behaviour of SHR and Wistar rats but also of WKY and Wistar rats. The use of SHR as animal model of ADHD is supported.