Age differences in an animal model of obsessive-compulsive disorder: participation of dopamine: dopamine in an animal model of OCD.

The putative age difference in the effect of chronically administered quinpirole (0.125 and 0.5 mg/kg, 11 injections) on alternation in a T maze was studied. Male juvenile (43 days old) and adult (around 90 days old) rats exhibited similar control values of alternation. In adults, quinpirole (0.5 mg/kg) produced a drastic perseveration after 10 and 11 injections (mean number of repetitive choices of 3.4 and 3.1, respectively); conversely, in juvenile, such treatment produced a less marked perseveration (mean number of repetitive choices of 1.7 and 2.1, for the 10th and 11th injection, respectively). We also studied the age difference in the protective actions of clomipramine subchronically administered (15 mg/kg, three times) on the quinpirole-induced perseveration. Clearly, as previously demonstrated, in adult animals, this tricyclic antidepressant completely prevented the drug-induced perseveration (mean number of repetitive choices of 1.7); while in juvenile, animals only produced a weak action (mean number of repetitive choices of 1.8). Data agreed with basic research showing a hyposensitivity of juvenile animals to dopaminergic agonists and with clinical findings suggesting a weaker effect of clomipramine treatment in youth. These results reinforce perseveration in a T maze as a useful animal model for studying age differences in obsessive-compulsive disorder (OCD).