Comparison of the ability of dopamine receptor agonists to inhibit forskolin-stimulated adenosine 3 ' 5 '-cyclic monophosphate (cAMP) accumulation via D-2L (long isoform) and D-3 receptors expressed in Chinese hamster ovary (CHO) cells

The pharmacological properties of the human D-2L (long isoform) and rat D-3 dopamine receptors in functional assays were examined. A range of dopamine agonists were assessed for their ability to inhibit adenosine 3'5' cyclic monophosphate (cAMP) accumulation via the two receptors expressed stably in Chinese hamster ovary cells. Dopamine caused a significantly greater maximal inhibition (P < 0.05) of cAMP accumulation via the D-2L receptor (similar to 70%) as compared to the D-3 receptor (similar to 50%). The pattern of agonist effects was different at the two receptors. The absolute and relative potencies for inhibition of cAMP accumulation were different for a range of agonists acting at the two receptors. Similarly, the maximal inhibitions achieved by a range of agonists were different for the two receptors.