MAPPING OF D-1 DOPAMINE-RECEPTOR MESSENGER-RNA BY NONRADIOACTIVE IN-SITU HYBRIDIZATION

In order to improve the identification and characterization of dopamin oceptive neurons, the rat brain was mapped for D-1 dopamine receptor m RNA by non-radioactive in situ hybridization (ISH) with a 45mer digoxi genin-labeled oligonucleotide probe. The specificity of the results wa s controlled with the help of a 396-bp D-1 receptor riboprobe. Labeled hybrids were visualized with an alkaline phosphatase-coupled anti-dig oxigenin antibody. The high resolution obtained permitted individual l abeled cells to be identified and to distinction between cell bodies a nd processes. D-1 mRNA was largely confined to neurons. With the excep tion of ependymal cells, glial cells were not distinctly labeled. Subc ellularly, D-1 mRNA was localized to perikarya but not to dendrites or axons. D-1 receptor-expressing neurons were present in all of the kno wn terminal fields of mesencephalic or diencephalic dopaminergic neuro ns. However, D-1 message was also detected in brain areas which are no t known to contain D-1 ligand binding sites or in which the presence o r the cellular source of this receptor subtype had previously not been unequivocally established, such as the hippocampus or cerebellar cort ex. Moreover, labeled neurons were present in regions not known to rec eive dopaminergic projections, such as the thalamic and some brainstem nuclei. We conclude that this ISH technique provides a considerable g ain in sensitivity and resolution with regard to neurotransmitter rece ptor mapping.