DISTRIBUTION OF DOPAMINE D1, D2, AND D5 RECEPTOR MESSENGER-RNAS IN THE MONKEY BRAIN - RIBONUCLEASE PROTECTION ASSAY ANALYSIS

The distribution of the mRNAs encoding the dopamine D1, D2 and D5 rece ptors was determined in brain tissues obtained from intact female rhes us monkeys, using a ribonuclease protection assay. Tissue blocks from the frontal cortex, striatum, thalamus, hippocampus and substantia nig ra were dissected and total RNA was extracted. Dopamine D2 and D5 rece ptor DNA fragments were generated from rhesus monkey genomic DNA using polymerase chain reaction. To generate dopamine receptor subtype-spec ific cRNA probes, DNA fragments corresponding to the carboxy terminus of the rhesus monkey D1 and D2 receptor genes and to the putative tran smembrane domain regions (IV-VI) of the D5 receptor gene, were subclon ed into the pGEM3Z/4Z vectors. Expression of D1 receptor mRNA exhibite d significant regional differences: striatum > > > cerebral cortex 2 h ippocampus 2 lateral thalamus. D1 receptor mRNA was found in low quant ities in the medial thalamus, but was not consistently expressed in th e substantia nigra area. In contrast, D2 receptor mRNA was detected in all regions that were studied: striatum > > > substantia nigra > > hi ppocampus 2 cerebral cortex greater than or equal to medial thalamus g reater than or equal to lateral thalamus. D5 receptor mRNA was also ex pressed in all regions, with highest levels in the cerebral cortex, st riatum and lateral thalamus, and moderate levels in the substantia nig ra, medial thalamus and the hippocampus. The D5 receptor mRNA appears to be widely distributed in the monkey brain. Most interesting is the expression of D5 receptor mRNA in tissues of the substantia nigra area .