Nocistatin inhibits 5-hydroxytryptamine release in the mouse neocortex via presynaptic Gi/o protein linked pathways.
OBJECTIVE
Nocistatin (NST) is a neuropeptide generated from cleavage of the nociceptin/orphanin FQ (N/OFQ) precursor. Evidence has been presented that NST acts as a functional antagonist of N/OFQ, although NST receptor and transduction pathways have not yet been identified. We previously showed that N/OFQ inhibited [(3)H]5-hydroxytryptamine ([(3)H]5-HT) release from mouse cortical synaptosomes via activation of NOP receptors. We now investigate whether NST regulates [(3)H]5-HT release in the same preparation.


METHODS
Mouse and rat cerebrocortical synaptosomes in superfusion, preloaded with [(3)H]5-HT and stimulated with 1 min pulses of 10 mM KCl, were used.


RESULTS
Bovine NST (b-NST) inhibited the K(+)-induced [(3)H]5-HT release, displaying similar efficacy but lower potency than N/OFQ. b-NST action underwent concentration-dependent and time-dependent desensitization, and was not prevented either by the NOP receptor antagonist [Nphe(1) Arg(14),Lys(15)]N/OFQ(1-13)-NH(2) (UFP-101) or by the non-selective opioid receptor antagonist, naloxone. Contrary to N/OFQ, b-NST reduced [(3)H]5-HT release from synaptosomes obtained from NOP receptor knockout mice. However, both N/OFQ and NST were ineffective in synaptosomes pre-treated with the G(i/o) protein inhibitor, Pertussis toxin. NST-N/OFQ interactions were also investigated. Co-application of maximal concentrations of both peptides did not result in additive effects, whereas pre-application of maximal b-NST concentrations partially attenuated N/OFQ inhibition.


CONCLUSIONS
We conclude that b-NST inhibits [(3)H]5-HT release via activation of G(i/o) protein linked pathways, not involving classical opioid receptors and the NOP receptor. The present data strengthen the view that b-NST is, per se, a biologically active peptide endowed with agonist activity.
Fantin
M
M
Department of Experimental and Clinical Medicine, Section of Pharmacology, Istituto Nazionale di Neuroscienze, University of Ferrara, Ferrara, Italy.
Fischetti
C
C
Trapella
C
C
Morari
M
M
D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D051379:Mice; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D019579:Neocortex / Q000187:drug effects* / Q000378:metabolism; D018847:Opioid Peptides / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014316:Tritium
C479838:(Nphe(1),Arg(14),Lys(15))N-OFQ NH(2); D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D018847:Opioid Peptides; D012702:Serotonin Antagonists; C111148:nocistatin; D014316:Tritium; D012701:Serotonin; D009270:Naloxone; D011189:Potassium Chloride; D019206:GTP-Binding Protein alpha Subunits, Gi-Go