Dual coupling of opioid receptor-like (ORL1) receptors to adenylyl cyclase in the different layers of the rat main olfactory bulb.
The coupling of opioid receptor-like (ORL1) receptors to adenylyl cyclase has been investigated in specific layers of the rat main olfactory bulb. Membranes prepared from the olfactory nerve-glomerular layer (ON-G layer), external plexiform layer (EP layer) and granule cell layer (GR layer) displayed specific binding sites for [(3)H]-nociceptin/orphanin FQ ([(3)H]Noc/OFQ). In each layer, the presence of high-and low-affinity binding sites, with K(D) values in the picomolar and nanomolar range, respectively, was detected. The binding of [(3)H]Noc/OFQ was displaced by unlabelled Noc/OFQ, but not by opioid antagonists. In each layer, Noc/OFQ significantly stimulated [(35)S]GTPgammaS binding with nanomolar potencies. In ON-G layer, Noc/OFQ inhibited basal adenylyl cyclase activity and the enzyme stimulations by corticotropin releasing hormone (CRH), Ca(2+)/calmodulin (Ca(2+)/CaM) and forskolin (FSK). In EP layer, Noc/OFQ inhibited Ca(2+)/CaM-and FSK-stimulated enzyme activities. Conversely, in GR layer the peptide stimulated basal cyclase activity and potentiated the enzyme activation by CRH. The Noc/OFQ stimulation was counteracted by the GDP-bound form of the alpha subunit of transducin and was mimicked by transducin betagamma subunits. In the same tissue layer, Ca(2+)/CaM-and FSK-stimulated enzyme activities were inhibited. Naloxone failed to antagonize all the actions of Noc/OFQ. Western blot and RT-PCR analysis revealed the expression of Ca(2+)-insensitive and -sensitive adenylyl cyclases in the three layers. These results demonstrate that in rat main olfactory bulb ORL1 receptors can differentially affect distinct forms of adenylyl cyclase in a layer specific manner.
Onali
P
P
Departments of Neuroscience and Medical Sciences, Section of Biochemical Pharmacology, University of Cagliari, Cagliari, Italy. onali@unica.it
Ingianni
A
A
Olianas
M C
MC
D000262:Adenylyl Cyclases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism / Q000494:pharmacology; D007527:Isoenzymes / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008297:Male; D009830:Olfactory Bulb / Q000201:enzymology*; D018847:Opioid Peptides / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D014316:Tritium; D014665:Vasodilator Agents / Q000378:metabolism / Q000494:pharmacology; D000094942:Nociceptin Receptor; D000097629:Nociceptin
D000262:Adenylyl Cyclases; D002118:Calcium; D002147:Calmodulin; D005576:Colforsin; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D007527:Isoenzymes; D018847:Opioid Peptides; D012333:RNA, Messenger; D011957:Receptors, Opioid; D013462:Sulfur Radioisotopes; D014316:Tritium; D014665:Vasodilator Agents; D000094942:Nociceptin Receptor; D000097629:Nociceptin; C000722285:Oprl1 protein, rat