A dopamine receptor antagonist; selectively inhibits radioligand binding to dopamine D2 receptors in rat brain homogenates (IC50s = 56 and >10,000 nM for D2 and D1 receptors, respectively); inhibits radioligand binding to both D2 and D1 receptors in vivo (ED50s = 4.9 and 51 mg/kg, respectively); reverses D-amphetamine- and apomorphine-induced depression of dopamine neurons and increases dopamine synthesis and dihydroxyphenylacetic acid levels in the striatum and olfactory tubercles in rats from 0.4-0.8 mg/kg; suppresses spontaneous locomotion and blocks conditioned avoidance responses in male mice and female rats; inhibits bromocriptine-induced climbing behavior in mice; increases error rates and reduces response rate in pigeons following learned acquisition from 0.3-5.6 mg/kg,