DISCRIMINATIVE STIMULUS EFFECTS OF COCAINE IN SQUIRREL-MONKEYS - LACKOF ANTAGONISM BY THE DOPAMINE D-2 PARTIAL AGONISTS TERGURIDE, SDZ-208-911, AND SDZ-208-912

The effects of cocaine alone and after pretreatment with the dopamine D-2 partial agonists terguride, SDZ 208-911, and SDZ 208-912 were dete rmined in squirrel monkeys trained to discriminate cocaine from saline using a two-lever drug discrimination procedure. When tested alone, c ocaine engendered dose-related increases in the percentage of response s on the cocaine-associated lever, reaching virtually exclusive cocain e-appropriate responding after a dose of 1.0 mg/kg. Pretreatment with terguride (0.003-0.03 mg/kg), SDZ 208-911 (0.001-0.01), and SDZ 208-91 2 (0.003-0.018 mg/kg) did not consistently alter the discriminative st imulus effects of cocaine. Although some doses of each D-2 partial ago nist either increased (notably SDZ 208-911) or decreased (notably SDZ 208-912) the level of cocaine-appropriate responding engendered by low to intermediate doses of cocaine, none of the drugs reduced the perce ntage of cocaine-appropriate responses engendered by 1.0 mg/kg cocaine . The results do not support the view that terguride, SDZ 208-981, or SDZ 208-912 would serve as functional antagonists of the subjective ef fects of cocaine.