D-1/D-2 behavioural interactions in the rat involving striatal dopamine D-1 receptors.

Simultaneous systemic administration of SKF 38393 (1-15 mg/kg i.p.) and LY 171555 (0.625-20 mg/kg s.c.) showed clear evidence of dopamine D-1/D-2 behavioural interactions compared to either treatment given alone. Similar interactions were observed between an intermediate systemic dose of LY 171555 (5 mg/kg) and SKF 38393 (1-10 micrograms) microinjected bilaterally into the caudate-putamen, but not into the substantia nigra pars reticulata, suggesting that striatal dopamine D-1 receptors are the ones responsible for mediating the altered behavioural responses to D-2 agonists in the intact rat.