D-2-SPECIFIC DISCRIMINATIVE STIMULI - PARAMETERS, BLOCKING, AND REBOUND

This study characterizes the cue properties of quinpirole (LY 171555), a selective D-2 agonist, and the blocking capabilities of spiperone, a selective D-2 antagonist. After rats were trained to discriminate 0. 025 mg/kg quinpirole from distilled water, a dose-response curve and t ime course of the quinpirole discriminative stimulus were determined. The effectiveness of three doses of spiperone in blocking the discrimi native stimulus produced by 0.02 mg/kg quinpirole was then assessed. F inally, the time course of spiperone's blocking action was determined. Given the putative selective action of these drugs on D-2 receptors a nd the parametric data presented here, it was predicted that following chronic treatment with spiperone, a rebound increase in quinpirole-ap propriate responding would occur. Neither chronic treatment with spipe rone nor chronic treatment with haloperidol produced the predicted cha nges. This result, however, may be confined to the specific dose and t ime parameters used.