Locomotor behaviors in response to new selective D-1 and D-2 dopamine receptor agonists, and the influence of selective antagonists.

With the introduction of the selective D-1 dopamine receptor agonist and antagonist benzazepines, especially as enantiomeric pairs, there is now a range of D-1 compounds to complement the previously available selective D-2 agents. These have been used to investigate whether sub-types of dopamine receptors might be differentially involved in locomotor behavior. Stereotyped locomotion induced by the non-selective D-2 agonist apomorphine and by the selective D-2 agonist RU 24213 were blocked by the selective D-2 antagonists metoclopramide and Ro 22-2586 [-)-piquindone). Responses to either D-2 agonist were also blocked by the selective D-1 antagonists SCH 23390 and R-(but not S-) SK&F 83566. Non-stereotyped locomotion was induced by R- but not S-SK&F 38393, a stereoselective D-1 agonist, and was blocked by SCH 23390. Responses to the D-1 agonist were also antagonised by metoclopramide. Such results suggest concerted D-1:D-2 interplay in the regulation of at least some dopaminergic behaviors, such as locomotion.