Role of alpha 1 receptors in the behavioural supersensitivity to D2 agonists induced by chronic treatment with imipramine.

Chronic treatment with imipramine increased the locomotor response to quinpirole, a selective D2 receptor agonist. This effect was blocked by minute doses of prazosin (0.1-1 mg/kg), a selective alpha 1 receptor blocker, in a dose-dependent manner. Conversely, in control rats the locomotor response to quinpirole was enhanced by the stimulation of alpha 1 receptors with the selective agonist St 587. The results suggest that alpha 1 receptor stimulation plays a permissive role in the supersensitivity of D2 receptors following chronic treatment with imipramine.