DOPAMINE D-1 AND D-2 RECEPTOR LIGANDS MODULATE THE BEHAVIOR OF MICE IN THE ELEVATED PLUS-MAZE

To further our understanding of the potential role of dopamine in mech anisms of anxiety, the effects fo four dopamine receptor ligands were examined in an ethological version of the murine elevated plus-maze te st. The D-1 receptor partial agonist SKF 38393 (2.5-20.0 mg/kg), had m inimal behavioural activity in this teat, whereas the selective D-1 re ceptor antagonist, SCH 23390 (0.025-0.2 mg/kg), had dose-dependent but behaviourally nonspecific effects. Quinpirole (0.0625-0.5 mg/kg), a D -2 receptor agonist, had no effects at low doses but severely disrupte d locomotion and exploration at the highest doses tested. In marked co ntrast to the lack of effect or nonspecific effects seen with the othe r ligands tested, the D-2 receptor antagonist, sulpiride (2.5-20.0 mg/ kg), produced an unambiguous anxiolytic-like profile under present tes t conditions. Although non of the doses tested adversely affected gene ral activity, clear antianxiety effects were observed on both traditio nal and novel (i.e., risk assessment) behavioural measures. Data are d iscussed in relation to the relative importance D-1 and D-2 receptor m echanisms in plus-maze anxiety, and the need to further assess D-2 inv olvement through the use of more selective compounds.