QUANTITATIVE DISTRIBUTION OF THE DELTA-OPIOID RECEPTOR MESSENGER-RNA IN THE MOUSE AND RAT CNS

We have used a sensitive solution hybridization assay that employs a r iboprobe obtained from the mouse delta opioid receptor (DOR) coding se quence to quantitate the relative abundance of DOR mRNA in the central nervous system (CNS) of the adult mouse and rat. In brain Poly A+ RNA extracts this riboprobe hybridized to a single 10 kb transcript from mouse and two transcripts, one of 12 and the other of 4.5 kb in size f rom rat. In mouse CNS the highest levels of DOR mRNA were found in the caudate-putamen at 3.3 +/- 0.1 (SEM) pg/ug RNA. DOR mRNA levels in th e range from 2.6 to 2.1 pg/ug RNA were measured in frontal cortex, nuc leus accumbens, whole brain and olfactory tubercle. Spinal cord, peria queductal gray and hippocampus had DOR mRNA levels in the range from 1 .8 to 1.5 pg/ug RNA, while medial thalamus and cerebellum had the lowe st levels (0.5 pg/ug RNA). These results correlate with the reported r elative distribution of DOR mRNA in mouse using an in situ hybridizati on technique. In rat CNS, the highest levels of DOR mRNA were measured in caudate-putamen at 2.3 +/- 0.1 pg equivalents/ug RNA. Whole brain, cerebral cortex, olfactory bulb and brain stem had levels in the rang e from 1.5 to 0.9 pg equivalents/ug RNA while the lowest DOR mRNA leve ls were measured at 0.5 pg equivalents/ug RNA or less in thalamus, hip pocampus, substantia nigra and cerebellum. This study demonstrates the ability of solution hybridization assays to quantitate homologous (mo use) as well as similar but heterologous (rat) DOR mRNA levels.