The putative D-3 dopamine receptor agonist 7-OH-DPAT (10 micrograms/kg, s.c.) reduced spontaneous activity in rats, without inducing yawning; higher doses (0.1-10.0 mg/kg, s.c.) stimulated non-stereotyped sniffing, locomotion and chewing, which were attenuated by the selective D-1 antagonist BW 737C (5.0 mg/kg, s.c.) without release of any atypical behaviours. Low doses of 7-OH-DPAT may act on inhibitory D-3 receptors, while higher doses may act at stimulatory D-3 or other "D-2-like" receptors that participate in cooperative but not oppositional interactions with D-1 receptors.