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The nociceptin receptor (NOP) and its ligand nociceptin/orphanin FQ (N/OFQ) have been shown to exert a modulatory effect on immune cells during sepsis. We evaluated the suitability of an experimental lipopolysaccharide (LPS)-induced sepsis model for studying changes in the nociceptin system. C57BL/6 mice BALB/c mice and Wistar rats were inoculated with different doses of LPS with or without a nociceptin receptor antagonist (UFP-101 or SB-612111). In C57BL/6 mice LPS 0.85 mg/kg injection produced no septic response, whereas 1.2mg/kg produced a profound response within 5h. In BALB/c mice, LPS 4 mg/kg produced no response, whereas 7 mg/kg resulted in a profound response within 24h. In Wistar rats LPS 15 mg/kg caused no septic response in 6/10 animals, whereas 25mg/kg resulted in marked lethargy before 24h. Splenic interleukin-1β mRNA in BALB/c mice, and serum TNF-α concentrations in Wistar rats increased after LPS injection in a dose-dependent manner, but were undetectable in control animals, indicating that LPS had stimulated an inflammatory reaction. IL-1β and TNF-α concentrations in LPS-treated animals were unaffected by administration of a NOP antagonist. Similarly NOP antagonists had no effect on survival or expression of mRNA for NOP or ppN/OFQ (the N/OFQ precursor) in a variety of tissues. In these animal models, the dose-response curve for LPS was too steep to allow use in survival studies and no changes in the N/OFQ system occurred within 24h. We conclude that LPS-inoculation in rodents is an unsuitable model for studying possible changes in the NOP-N/OFQ system in sepsis., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The heptadecapeptide nociceptin/orphanin FQ (N/OFQ) is the endogenous ligand for the N/OFQ peptide (NOP) receptor. It is cleaved from a larger precursor identified as prepronociceptin (ppN/OFQ). NOP is a member of the seven transmembrane-spanning G-protein coupled receptor (GPCR) family. ppN/OFQ and NOP receptors are widely distributed in different human tissues. Asthma is a complex heterogeneous disease characterized by variable airflow obstruction, bronchial hyper-responsiveness and chronic airway inflammation. Limited therapeutic effectiveness of currently available asthma therapies warrants identification of new drug compounds. Evidence from animal studies suggests that N/OFQ modulates airway contraction and inflammation. Interestingly up regulation of the N/OFQ-NOP system reduces airway hyper-responsiveness. In contrast, inflammatory cells central to the inflammatory response in asthma may be both sources of N/OFQ and respond to NOP activation. Hence paradoxical dysregulation of the N/OFQ-NOP system may potentially play an important role in regulating airway inflammation and airway tone. To date there is no data on N/OFQ-NOP expression in the human airways. Therefore, the potential role of N/OFQ-NOP system in asthma is unknown. This review focuses on its physiological effects within airways and potential value as a novel asthma therapy., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Urotensin-II (U-II) activates the U-II receptor (UT) to modulate a range of biological responses at both central and peripheral sites. Previous studies have demonstrated that the sequence Trp(7)-Lys(8)-Tyr(9) of the cyclic portion of the peptide is crucial for biological activity. Here, we describe a focused structure-activity study of Tyr(9) which has been replaced with a series of non-coded amino acids in the U-II(4-11) template. Thirteen analogs were synthesized and pharmacologically tested for intracellular calcium mobilization in HEK293 cells stably expressing the rat UT receptor. The results of this study demonstrated the following Tyr(9) structure-activity features: (i) the position of the OH group of the side chain is not important for biological activity, (ii) the distance of the phenol moiety from the peptide backbone and its conformational freedom are crucial for UT receptor recognition, (iii) this position is important not only for receptor occupation but also for its activation since the 3,5-diiodoTyr(9) chemical modification generated a potent partial agonist. This pharmacological activity of [3,5-diiodoTyr(9)]U-II(4-11) was confirmed in bioassay experiments performed using the rat thoracic aorta as a U-II sensitive preparation.

In the present study we describe the synthesis and biological evaluation of 24 analogues of the urotensin II (U-II) fragment U-II(4-11) substituted in position 4 with coded and non-coded aromatic amino acids. All of the new analogues behaved as full U-II receptor (UT) agonists. Our results indicated that aromaticity is well tolerated, size, length and chirality of the side chain are not important, while substituents with a nitrogen atom are preferred. Thus acylation of U-II(5-11) with small groups bearing nitrogen atoms could be instrumental in future studies for the identification of novel potent UT receptor ligands.

Knockout and pharmacological studies have shown that delta opioid peptide (DOP) receptor signalling regulates emotional responses. In the present study, the in vitro and in vivo pharmacological profile of the DOP ligand, H-Dmt-Tic-NH-CH(CH2-COOH)-Bid (UFP-512) was investigated. In receptor binding experiments performed on membranes of CHO cells expressing the human recombinant opioid receptors, UFP-512 displayed very high affinity (pKi 10.20) and selectivity (>150-fold) for DOP sites. In functional studies ([35S]GTP gamma S binding in CHOhDOP membranes and electrically stimulated mouse vas deferens) UFP-512 behaved as a DOP selective full agonist showing potency values more than 100-fold higher than DPDPE. In vivo, in the mouse forced swimming test, UFP-512 reduced immobility time both after intracerebroventricular (i.c.v.) and intraperitoneal (i.p.) administration. Similar effects were recorded in rats. Moreover, UFP-512 evoked anxiolytic-like effects in the mouse elevated plus maze and light-dark aversion assays. All these in vivo actions of UFP-512 were fully prevented by the selective DOP antagonist naltrindole (3 mg/kg, s.c.). In conclusion, the present findings demonstrate that UFP-512 behaves as a highly potent and selective agonist at DOP receptors and corroborate the proposal that the selective activation of DOP receptors elicits robust anxiolytic- and antidepressant-like effects in rodents.

Knockout and pharmacological studies demonstrated that the activation of delta opioid peptide (DOP) receptors produces antidepressant-like effects in rodents. Here we report the results obtained with the novel DOP ligand H-Dmt-Tic-NH-CH(2)-Bid (UFP-502). UFP-502 bound with high affinity (pK(i) 9.43) to recombinant DOP receptors displaying moderate selectivity over MOP and KOP. In CHO(hDOP) [(35)S]GTPgammaS binding and mouse vas deferens experiments, UFP-502 behaved as a potent (pEC(50) 10.09 and 10.70, respectively) full agonist. In these preparations, naloxone, naltrindole and N,N(CH(3))(2)Dmt-Tic-OH showed similar pA(2) values against UFP-502 and DPDPE and the same rank order of potency. In vivo in mice, UFP-502 mimicked DPDPE actions, producing a significant reduction of immobility time after intracerebroventricular administration in the forced swimming test and a clear antinociceptive effect after intrathecal injection in the tail withdrawal assay. However, while the effects of DPDPE were fully prevented by naltrindole those evoked by UFP-502 were unaffected (tail withdrawal assay) or only partially reversed (forced swimming test). In conclusion, UFP-502 represents a novel and useful chemical template for the design of selective agonists for the DOP receptor.

The recent identification of the nociceptin receptor-nociceptin system and the description of its role in nociceptive processing has produced numerous investigative studies. A fundamental part of this research is to understand the cellular signaling events (i.e. the building blocks) upon which the pharmacology of this intriguing system is based. As anticipated, nociceptin receptor activation inhibits the formation of cAMP formation via a pertussis toxin-sensitive G-protein. This indicates that nociceptin receptor couples to the G(i)/G(o) class of G-protein(s). However, there is now growing evidence for nociceptin activation of additional signaling pathways, including MAP kinase and phospholipase C/[Ca(2+)](i). These signaling events are discussed in this review.

Responses to a newly synthesized human adrenomedullin (hADM) analog, hADM (16-31), were investigated in the rat and cat. Unlike the full-sequence peptide, which has potent hypotensive activity, hADM (16-31) had pressor activity in the rat but not in the cat. Injection of hADM (16-31) in doses of 10-300 nmol/kg i.v. induced dose-dependent increases in systemic arterial pressure in the rat, and the peptide was approximately 10-fold less potent than norepinephrine when doses are compared on a nanomole basis. In contrast, injection of hADM (16-31) in doses up to 1,000 nmol/kg i.v. had no significant effect on systemic arterial pressure in the cat. Increases in systemic arterial pressure in response to hADM (16-31) in the rat were significantly reduced after administration of phentolamine or reserpine. These data suggest that increases in systemic arterial pressure in response to hADM (16-31) are mediated by release of catecholamines and activation of alpha-adrenergic receptors in the rat. These data show that hADM (16-31) has significant pressor activity and that there are marked species differences in the response to hADM (16-31).

Responses to proadrenomedullin NH2-terminal 20 peptide (PAMP) were investigated in the systemic and hindquarters vascular bed of the rat. Intravenous injections of PAMP and adrenomedullin (ADM) produced dose-related decreases in systemic arterial and hindquarters perfusion pressure, which were not altered by alpha-receptor or adrenergic nerve terminal blocking agents. PAMP was 100-fold less potent than ADM, and hindquarters vasodilator responses to both peptides were similar in innervated and denervated preparations. When baseline tone was increased with phenylephrine and U46619 or decreased with sodium nitroprusside, vasodilator responses to PAMP and ADM were correlated with the basal level of tone, suggesting that responses to both peptides are dependent on the baseline level of vasoconstrictor tone in the hindquarters vascular bed of the rat.