Coupling of D2 and D3 dopamine receptors to G‐proteins

Recombinant cell lines expressing D2 and D3 dopamine receptor isoforms have been used to study coupling of these receptors to G‐proteins from the effects of GTP to reduce agonist binding affinities in agonist/[3H]spiperone competition experiments. D2(short) expressed in Ltk− cells, D2(long) expressed in Ltk− or CHO cells and D3 expressed in CHO cells all showed coupling to the endogenous G‐proteins of the cells. The detailed agonist binding characteristics indicated that there were differences in receptor/G‐protein coupling for the same receptor (D2(long) expressed in two cell types or for different receptors (D2(long),D2(short) expressed in the same cell type.