SCH-23390 EQUIVALENTLY, BUT YM-09151-2 DIFFERENTIALLY REDUCES THE STIMULANT EFFECTS OF METHAMPHETAMINE, MK-801 AND KETAMINE - ASSESSMENT BYDISCRETE SHUTTLE AVOIDANCE IN MICE

The inhibitory actions of the selective dopamine D1- and D2-antagonist s SCH 23390 and YM-09151-2, respectively, on the mouse's discrete shut tle avoidance were almost equipotent at doses ranging from 0.01 - 0. 1 mg/kg. SCH 23390 reduced the stimulant action of methamphetamine (0.5 mg/kg), MK-801 (0.1 mg/kg) and ketamine (I 0 mg/kg) with a similar po tency. YM-09151-2 also antagonized the actions of these drugs, with th e following order of effectiveness: ketamine > MK-801 > methamphetamin e. The present results indicate that methamphetamine, MK-801 and ketam ine have different characteristics of CNS stimulant action through dop amine D2-receptors.