Inhibitory effect of nociceptin on [3H]-5-HT release from rat cerebral cortex slices.
1. The effect of nociceptin (NC) on 5-hydroxytryptamine (5-HT) release was studied in rat cerebral cortex slices preincubated with [3H]-5-HT and electrically stimulated (3 Hz, for 2 min) at the 45th (St1) and the 75th (St2) min of superfusion. 2. NC (0.1 - 3 microM), present in the medium from the 70th min onward, concentration-dependently reduced electrically evoked [3H]-5-HT efflux (pEC50=6.54, Emax -54%). The inhibition was not antagonized by naloxone (1 microM) ruling out the involvement of opioid receptors. 3. Phe1psi(CH2-NH2)Gly2]NC(1-13)NH2, which acts as an opioid-like receptor (ORL1) antagonist at the peripheral level, behaved as a partial agonist in cerebral cortex slices i.e. it inhibited [3H]-5-HT efflux when added before St2, however, when present in the medium throughout the whole experiment, [Phe1psi(CH2-NH2)Gly2]NC(1-13)NH2 prevented the action of NC added at the 70th min. 4. The non-selective ORL1 receptor antagonist, naloxone benzoylhydrazone (3 microM), in the presence of 10 microM naloxone, did not modify the St2/St1 ratio but completely abolished the NC effect. 5. These findings demonstrate that NC inhibits 5-HT release from rat cerebral cortex slices via ORL1 receptors, suggesting its involvement in central processes mediated by 5-HT.
Siniscalchi
A
A
Department of Clinical and Experimental Medicine, Section of Pharmacology, University of Ferrara, 44100 Ferrara, Italy.
Rodi
D
D
Beani
L
L
Bianchi
C
C
D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009270:Naloxone / Q000031:analogs & derivatives / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D018847:Opioid Peptides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011957:Receptors, Opioid / Q000819:agonists / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D013997:Time Factors; D000094942:Nociceptin Receptor; D000097629:Nociceptin
D009270:Naloxone; D009292:Narcotic Antagonists; D018847:Opioid Peptides; D010446:Peptide Fragments; D011480:Protease Inhibitors; D011957:Receptors, Opioid; D012701:Serotonin; D000094942:Nociceptin Receptor; D000097629:Nociceptin; C114149:nociceptin (1-13)-NH2, Phe(1)-psi(CH2-NH)-Gly(2)-; C058380:naloxone benzoylhydrazone; C000722285:Oprl1 protein, rat