Cataleptogenic effect of haloperidol, chlorpromazine and morphine in developing rats

The intensity of catalepsy produced by haloperidol (0.5 mg/kg), chlorpromazine (10 mg/kg) and morphine (20 mg/kg) given ip was tested in male Wistar rats of age between 3 weeks and 6 months. The cataleptic response was most expressed in the youngest animals, and decreased with age. The results indicate that young rats show higher reactivity of central dopaminergic receptors to the investigated drugs.