Characterization of subtype-specific antibodies to the human D₅ dopamine receptor: Studies in primate brain and transfected mammalian cells

To achieve a better understanding of how D₅ dopamine receptors mediate the actions of dopamine in brain, we have developed antibodies specific for the D₅ receptor. D₅ antibodies reacted with recombinant baculovirus- infected Sf9 cells expressing the D₅ receptor but not with the D₁ receptor or a variety of other catecholaminergic and muscarinic receptors. Epitope- tagged D₅ receptors expressed in mammalian cells were reactive with both D₅ antibodies and an epitope-specific probe. A mixture of N-linked glycosylated polypeptides and higher molecular-mass species was detected on immunoblots of membrane fractions of D₅-transfected cells and also of primate brain. D₅ receptor antibodies intensely labeled pyramidal neurons in the prefrontal cortex, whereas spiny medium-sized neurons and aspiny large interneurons of the caudate nucleus were relatively lightly labeled. Antibodies to the D₅ dopamine receptor should prove important in experimentally determining specific roles for the D₅ and D₁ receptors in cortical processes and diseases.