MU-OPIOID RECEPTOR MESSENGER-RNA EXPRESSION IN THE RAT CNS - COMPARISON TO MU-RECEPTOR BINDING

The distribution of cells expressing mu-receptor mRNA and mu-receptor binding sites were compared in brain and spinal cord tissue sections u sing a combination of in situ hybridization and receptor autoradiograp hic techniques. mu-Receptor mRNA was visualized with a S-35-labeled cR NA probe directed to transmembrane III-VI of the rat mu-receptor, whil e mu-receptor binding sites were labeled with the mu-selective ligand H-3DAMGO. A high correspondence between the mu-receptor mRNA and rec eptor binding distributions was observed in the nucleus of the accesso ry olfactory bulb, anterior olfactory nuclei, striatal patches of the nucleus accumbens and caudate-putamen, endopiriform nucleus, claustrum , diagonal band of Broca, globus pallidus, ventral pallidum, bed nucle us of stria terminalis, most thalamic nuclei, medial and posteriocorti cal medial amygdala, lateral, dorsomedial, posterior and mammillary nu clei of the hypothalamus, presubiculum, subiculum, rostral interpedunc ular nucleus, median raphe, inferior colliculus, parabrachial nucleus, locus coeruleus, central grey, nucleus ambiguus, nucleus of the solit ary tract, nucleus gracilis, nucleus cuneatus, and the dorsal motor nu cleus of vagus. Differences in mu-receptor mRNA and receptor binding d istributions were observed in several regions, including the olfactory bulb, cortex, hippocampus, superior colliculus, spinal trigeminal nuc leus, cochlear nucleus and spinal cord, and may be due to mu-receptor transport to presynaptic terminals.