Nociceptin, OP4 receptor ligand in different models of experimental epilepsy

The anticonvulsive activity of nociceptin, endogenous OP4 receptors agonist was investigated in pentylenetetrazole (PTZ), N-methyl D-aspartic acid (NMDA), bicucculine (BCC) and electrically evoked seizure models of experimental epilepsy. Nociceptin, at the dose of 10 nmol, suppressed the clonic seizures induced by PTZ, NMDA and BCC. [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 which has been proposed to be selective antagonist OP4 receptors, did not prevent the action of nociceptin. The effect of [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 on seizures induced by PTZ, NMDA and BCC was very similar to that of nociceptin. These data support the hypothesis that it possesses agonistic properties. Naloxone did not reverse the anticonvulsive action of nociceptin as well as [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 which excludes the participation of opioid receptor in this action. On the other hand in the electroconvulsive model of generalized seizures, nociceptin as well as [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 influenced neither the electroconvulsive threshold nor the maximal electroshock test. The data suggest that nociceptin and [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 can exert anticonvulsive action. These properties depend on OP4 but not opioid receptors activation.     

Intrathecal [Nphe1]nociceptin( 1-13)NH2 selectively reduces the spinal inhibitory effect of nociceptin

The effects of intrathecal (i.t.) application of the proposed nociceptin receptor antagonist [Nphe1]nociceptin(1-13)NH2 on the flexor reflex was evaluated in spinalized rats. I.t. [Nphe1]nociceptin (1-13)NH2 dose-dependently facilitated the flexor reflex with no depression. Pretreatment with 16.5 nmol of [Nphe1]nociceptin(1-13)NH2 prevented the development of reflex depression following 0.55 nmol i.t. nociceptin, but strongly enhance the initial excitatory effect of nociceptin. The reflex depressive effect of i.t. endomorphine-2 was not blocked by [Nphe1]nociceptin(1-13)NH2 pretreatment. It is concluded that [Nphe1]nociceptin(1-13)NH2 is a selective antagonist of the spinal receptor mediating the inhibitory action of nociceptin. It can be further suggested that the spinal inhibitory effect of nociceptin may be tonically active.     

Diphenyl sulfoxides as selective antagonists of the muscarinic M2 receptor

Structure activity studies on [4-(phenylsulfonyl)phenyl]methylpiperazine led to the discovery of 4-cyclohexyl-alpha-[4-[[4-methoxyphenyl(S)-sufinyl]phenyl]-1-pi perazineacetonitrile, 1, an M2 selective muscarinic antagonist. Affinity at the cloned human M2 receptor was 2.7 nM; the M1/M2 selectivity is 40-fold.     

Design and synthesis of 4-substituted-8-(2-phenyl-cyclohexyl)-2,8-diaza-spiro[4.5]decan-1-one as a novel class of GlyT1 inhibitors: achieving selectivity against the mu opioid and nociceptin/orphanin FQ peptide (NOP) receptors

A novel class of 4-substituted-8-(2-phenyl-cyclohexyl)-2,8-diaza-spiro[4.5]decan-1-ones have been discovered and developed as potent and selective GlyT1 inhibitors. The molecules are devoid of activity at the GlyT2 isoform and display excellent selectivities against the mu opioid receptor as well as the nociceptin/orphanin FQ peptide (NOP) receptor. A novel, straightforward and efficient synthetic strategy for the assembly of the target molecules is also presented.     

Novel 4-amino-furo[2,3-d]pyrimidines as Tie-2 and VEGFR2 dual inhibitors

A novel class of furo[2,3-d]pyrimidines has been discovered as potent dual inhibitors of Tie-2 and VEGFR2 receptor tyrosine kinases (TK) and a diarylurea moiety at 5-position shows remarkably enhanced activity against both enzymes. One of the most active compounds, 4-amino-3-(4-((2-fluoro-5-(trifluoromethyl)phenyl)amino-carbonylamino)phenyl)-2-(4-methoxyphenyl)furo[2,3-d]pyrimidine (7k) is <3 nM on both TK receptors and the activity is rationalized based on the X-ray crystal structure.     

Acetyl-RYYRIK-NH(2) is a highly efficacious OP(4) receptor agonist in the cardiovascular system of anesthetized rats

Nociceptin, the endogenous ligand of the OP₄ or ORL₁ (opioid receptor-like₁) receptor, decreases blood pressure and heart rate in anesthetized rats. Since the OP₄ receptor antagonist [Phe¹Ψ(CH₂-NH)Gly²]-nociceptin(1–13)NH₂ possesses an agonistic effect in this model, we examined whether other purported OP₄ receptor antagonists, acetyl-RYYRIK-NH₂ and naloxone benzoylhydrazone, antagonize the depressant effects of nociceptin. Acetyl-RYYRIK-NH₂, like nociceptin and [Phe¹Ψ(CH₂-NH)Gly²]-nociceptin(1–13)NH₂ and unlike naloxone benzoylhydrazone, decreased diastolic blood pressure and heart rate (rank order of potencies: nociceptin ≈ acetyl-RYYRIK-NH₂ [Phe¹Ψ(CH₂-NH)Gly²]-nociceptin(1–13)NH₂). The depressant effects were insensitive to the OP_1–3 receptor antagonist naloxone but diminished by naloxone benzoylhydrazone. In conclusion, the hypotensive and bradycardic effects of nociceptin in the anesthetized rat are mediated via OP₄ receptors, at which acetyl-RYYRIK-NH₂ is a highly potent and efficacious agonist.     

Nphe1]nociceptin(1-13)-NH2 antagonizes nociceptin-induced hypotension, bradycardia, and hindquarters vasodilation in the anesthetized rat

The purpose of this study was to investigate the effects of [Nphe1]nociceptin(1-13)-NH2 on nociceptin-induced decreases in mean arterial pressure (MAP), heart rate (HR), and hindquarters vascular bed resistance (HVBR) of the anesthetized rat. The results showed that i.c.v. or i.v. [Nphe1]nociceptin(1-13)-NH2 (1.5-12 nmol/kg and 5-120 nmol/kg, respectively) could antagonize the depressor effects of i.c.v. or i.v. nociceptin (3 and 30 nmol/kg, respectively) on MAP and HR. Furthermore, [Nphe1]nociceptin(1-13)-NH2 (5-120 nmol/kg) could reverse nociceptin (30 nmol/kg)-induced decrease of HVBR. However, [Nphe1]nociceptin(1-13)-NH2 had no significant effects on similar effects induced by morphine. Our results suggest that [Nphe1]nociceptin(1-13)-NH2 acts as a selective antagonist of the nociceptin receptor in the cardiovascular system of the rat.     

4-(4-alkylpiperazin-1-yl)phenyl group: a novel class of basic side chains for selective estrogen receptor modulators

In the structure–activity relationships of spiro[indene-1,1′-indane] series, the 4-(4-alkylpiperazin-1-yl)phenyl group was found to be functionally equipotent to the 4-(1-piperidinoethoxy)phenyl group, the most widely used basic side chain in selective estrogen receptor modulators.     

Inhibitory activity of nociceptin/orphanin FQ on capsaicin-induced bronchoconstriction in the guinea-pig

In vivo studies were conducted in the guinea-pig to investigate the activity of the selective ORL1 receptor agonist nociceptin/orphanin FQ against capsaicin-induced bronchoconstriction, a response mediated by the release of tachykinins from pulmonary sensory nerves. Anesthetized guinea-pigs were ventilated with a rodent ventilator and placed in a whole-body plethysmograph, and pulmonary resistance (R(L)) and dynamic lung compliance (C(Dyn)) were monitored. Intravenous administration of nociceptin/orphanin FQ (0.3 mg/kg) inhibited the capsaicin-induced bronchoconstriction. The new nonpeptide ORL1 receptor antagonist 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one (J-113397) administered intravenously (1 mg/kg) produced a significant blockade of the inhibitory effect of nociceptin/orphanin FQ (0.3 mg/kg) on capsaicin-induced bronchoconstriction, whereas the nonselective opioid receptor antagonist naloxone (1 mg/kg) had no effect. Nociceptin/orphanin FQ (0.3 mg/kg) did not affect the bronchoconstriction induced exogenously by the tachykinin NK2 receptor agonist [beta-ala8]-neurokinin A (4-10). We conclude that nociceptin inhibits in vivo capsaicin-evoked tachykinin release from sensory nerve terminals in the guinea-pig by a prejunctional mechanism. This inhibitory action does not involve activation of opioid receptors.     

In Vitro antifungal activity of 2-(4-substituted phenyl)-3(2H)-isothiazolones

The in vitro antifungal activity of several N2-phenyl-3(2H)-isothiazolones substituted at C4 of the phenyl moiety with heterocyclic nucleus or groups of different physico-chemical properties against four human pathogenic fungi was determined by broth macrodilution method; results were compared with those obtained with itraconazole and ketoconazole. These isothiazolones showed moderate to high activity against some or all tested strains and in comparison with the reference drugs, 5-chloro-2-(4-nitrophenyl)isothiazol-3-one (1g), 5-chloro-2-phenylisothiazol-3-one (1c), 4-[4-(5-chloro-3-oxo-3H-isothiazol-2-yl)phenyl]-1,4-dihydrotriazol-5-one (1s) and 2-(4-nitrophenyl)isothiazol-3-one (2g) against Aspergillus niger, 5-chloro-2-(4-nitrophenyl)isothiazol-3-one (1g) and 4-[4-(5-chloro-3-oxo-3H-isothiazol-2-yl)phenyl]piperazine-1-carboxamide (1q) against Trichophyton mentagrophytes had comparable activity, compounds 1g and 2g showing higher activity against Microsporum canis. Antifungal activity was favored by the presence of chlorine at C5 of the isothiazolone and/or the presence of nitro group or heterocyclic nucleus at C4 of the phenyl ring and proper hydrophilicity of the molecule.     

4-Substituted-8-(1-phenyl-cyclohexyl)-2,8-diaza-spiro[4.5]decan-1-one as a novel class of highly selective GlyT1 inhibitors with superior pharmacological and pharmacokinetic parameters

A novel class of 4-substituted-8-(1-phenyl-cyclohexyl)-2,8-diaza-spiro[4.5]decan-1-ones have been discovered and developed as potent and selective GlyT1 inhibitors. The molecules are devoid of activity at the GlyT2 isoform and display excellent selectivities against the mu opioid receptor as well as the nociceptin/orphanin FQ peptide (NOP) receptor. These molecules also exhibit superior pharmacological and pharmacokinetic parameters, relative to all GlyT1 inhibitors of the spiropiperidine family, culminating in the identification of 16b with an oral bioavailability of approximately 60%. In addition, a straightforward two-step procedure for the assembly of the target molecules is also presented.     

Synthesis and QSAR studies on hypotensive 1-[3-(4-substituted phenylthio) propyl]-4-(substituted phenyl) piperazines

A series of 1-[3-(4-substituted phenylthio) propyl]-4-(substituted phenyl) piperazines has been synthesized and evaluated for hypotensive activity. The QSAR studies indicate that resonance and hydrophobic parameters of the aryl substituents are important for hypotensive activity. The similar role of resonance parameter in describing the variance of 5-HT(2A) receptor binding affinities of these compounds suggests a possible role of 5-HT(2A) receptors in mediating the hypotensive action of title compounds.     

Synthesis and anticonvulsant activity of new 1-[2-oxo-2-(4-phenylpiperazin-1-yl)ethyl]pyrrolidine-2,5-diones

Twenty-two new 1-[2-oxo-2-(4-phenylpiperazin-1-yl)ethyl]pyrrolidine-2,5-diones were synthesized and tested for anticonvulsant activity. Initial anticonvulsant screening was performed using standard maximal electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ) screens in mice. Several compounds were tested additionally in the 6-Hz psychomotor seizure model. The neurotoxicity was determined applying the rotarod test. Excluding one compound, all other molecules were found to be effective in at least one seizure model. The most active were 1-(2-oxo-2-{4-[3-(trifluoromethyl)phenyl]piperazin-1-yl}ethyl)pyrrolidine-2,5-dione (14), 1-{2-[4-(4-chlorophenyl)piperazin-1-yl]-2-oxoethyl}-3-methylpyrrolidine-2,5-dione (17), 1-{2-[4-(4-chlorophenyl)piperazin-1-yl]-2-oxoethyl}-3,3-dimethylpyrrolidine-2,5-dione (23) and 3,3-dimethyl-1-(2-oxo-2-{4-[3-(trifluoromethyl)phenyl]piperazin-1-yl}ethyl)pyrrolidine-2,5-dione (26). These compounds showed high activity in the 6-Hz psychomotor seizure test as well as were active in the maximal electroshock and subcutaneous pentylenetetrazole (14 and 23) screens. Initial SAR studies for anticonvulsant activity have been discussed.     

Effects of [Nphe1]nociceptin(1-13)NH2, [Phe1(CH2-NH)Gly2]nociceptin(1- 13)NH2, and nocistatin on nociceptin inhibited constrictions of guinea pig isolated bronchus

Electric field stimulation (EFS) causes excitatory non adrenergic-non cholinergic (eNANC) and cholinergic constrictions in the guinea pig isolated bronchus, the activation of eNANC and cholinergic nerves respectively. We investigated the effects of [Nphe1]nociceptin(1-13)NH2 ([Nphe1]NC(1-13)NH2), [Phe1(CH2-NH)Gly2]nociceptin(1- 13)NH2 ([F/G] NC(1-13)NH2), and nocistatin (NST) on nociceptin (NC) inhibited constrictions in isolated bronchus of guinea pig. The results show that NC (1 micromol/L) inhibited EFS-induced eNANC and cholinergic constrictions compared with the control, in which nociceptin was not applied. After pretreatment with [Nphe1]NC(1-13)NH2, [F/G]NC(1-13)NH2, or NST, the inhibitions of NC were antagonized by [Nphe1]NC(1-13)NH2 and [F/G]NC(1-13)NH2 but not NST. However, [Nphe1]NC(1-13)NH2, [F/G]NC(1-13)NH2, and NST did not affect the inhibitions induced by morphine. Furthermore, [Nphe1]NC(1-13)NH2, [F/G]NC(1-13)NH2 and NST did not cause any appreciable effects on EFS-induced eNANC and cholinergic constrictions in guinea pig bronchi. The results demonstrate that [Nphe1]NC(1-13)NH2 and [F/G]NC(1- 13)NH2 but not NST act as selective antagonists of the NC receptor and the effects of NC on EFS-induced constrictions of guinea pig isolated bronchus.     

The relaxant effect of nociceptin on porcine coronary arterial ring segments

Nociceptin (NC), alias orphanin FQ, has been identified as the endogenous ligand of the opioid receptor-like 1 receptor (ORL1). The purpose of this study was to assess the effect of nociceptin on porcine coronary arteries and to investigate the mechanism of its action, if any. Rings of coronary arteries from porcine hearts were suspended in baths containing Krebs solution, and isometric tension was measured. The response to nociceptin (10(-1)2-10(-5) mol/L) was investigated in porcine coronary arterial rings and also in such rings contracted with prostaglandin F2alpha (PGF2alpha). The effects of endothelium, nitroxide (NO), methylene blue, cyclic GMP (cGMP), naloxone, [Nphe1]NC(1-13)NH2, and propranolol on nociceptin-induced relaxation were also assessed. Our study showed nociceptin relaxed the porcine coronary arterial rings and inhibited the vasocontractivity to PGF2alpha. The relaxing response of nociceptin in coronary arteries was significantly reduced by removal of endothelium and by the presence of L-NNA, cGMP, and [Nphe1]NC(1-13)NH2, the selective nociceptin receptor antagonist, but not by naloxone, the nonselestive opioid receptor blocker or propranolol, which blocks the adrenergic beta-receptor. Our results suggest that nociceptin induces relaxation of isolated coronary artery through NO, cGMP, and ORL1.     

GABA receptor antagonists and insecticides: common structural features of 4-alkyl-1-phenylpyrazoles and 4-alkyl-1-phenyltrioxabicyclooctanes

Fipronil [5-amino-3-cyano-1-(2,6-dichloro-4-trifluoromethylphenyl)-4-trifluoromethylsulfinylpyrazole] is one of the most important insecticides. Structure-activity studies described here reveal that fipronil retains its very high binding potency at the human beta3 and house fly gamma-aminobutyric acid (GABA) receptors and toxicity to house flies on replacing the pyrazole trifluoromethylsulfinyl moiety with tert-butyl or isopropyl and the phenyl trifluoromethyl substituent with ethynyl, trifluoromethoxy, bromo or chloro. Among the compounds studied, those with other alkyl groups at the 4-position of the pyrazole, as well as phenyl substitution without one or both of the 2,6-dichloro groups, are less effective. 5-Amino-4-tert-butyl-3-cyano-1-(2,6-dichloro-4-ethynylphenyl)pyrazole is highly effective and almost isosteric with 4-tert-butyl-3-cyano-1-(4-ethynylphenyl)-2,6,7-trioxabicyclo[2.2.2]octane (the most potent 4-alkyl-1-phenyltrioxabicyclooctane) as a noncompetitive GABA antagonist and insecticide. These findings are interpreted as three binding subsites in the GABA receptor: a hydrophobic site undergoing steric interaction with the tert-butyl or equivalent group; a hydrogen bonding site to pyrazole N-2; a pi bonding site to the face of the phenyl moiety; with supplemental enhancement by the 3-cyano and 4-ethynyl substituents.     

Discovery and SAR development of 2-(phenylamino) imidazolines as prostacyclin receptor antagonists [corrected

On the basis of screening hits (1a,b), a series of selective, high affinity prostacyclin receptor antagonists was developed. The optimized lead compound 25d [(4,5-dihydro-1H-imidazol-2-yl)-[4-(4-isopropoxybenzyl)phenyl]amine] had analgesic activity in the rat.     

An atom efficient, solvent-free, green synthesis and antimycobacterial evaluation of 2-amino-6-methyl-4-aryl-8-[(E)-arylmethylidene]-5,6,7,8-tetrahydro-4H-pyrano[3,2-c]pyridine-3-carbonitriles

An atom efficient, green protocol for the synthesis of fifteen 2-amino-6-methyl-4-aryl-8-[(E)-arylmethylidene]-5,6,7,8-tetrahydro-4H-pyrano[3,2-c]pyridine-3-carbonitriles in quantitative yields from the reaction of 1-methyl-3,5-bis[(E)-arylmethylidene]-tetrahydro-4(1H)-pyridinones with malononitrile in presence of solid sodium ethoxide under solvent-free condition is described. The compounds were tested for their in vitro activity against Mycobacterium tuberculosis H37Rv (MTB), multi-drug resistant tuberculosis (MDR-TB), and Mycobacterium smegmatis using agar dilution method. 2-Amino-4-[4-(dimethylamino)phenyl]-8-(E)-[4-(dimethylamino)phenyl]methylidene-6-methyl-5,6,7,8-tetrahydro-4H-pyrano[3,2-c]-pyridine-3-carbonitrile was found to be the most potent compound (MIC: 0.43microM) against MTB and MDR-TB, being 100 times more active than standard, isoniazid against MDR-TB.     

Highly potent nociceptin analog containing the Arg-Lys triple repeat

One of the structural characteristics of a neuropeptide nociceptin is the existence of Arg-Lys (RK) residues at positions 8-9 and 12-13; both RKs have been suggested to bind to the acidic amino acid cluster in the second extracellular loop of the seven transmembrane domain receptor ORL1. With a design strategy of attempting to obtain an analog that binds more strongly to the receptor's acidic cluster, we synthesized a series of nociceptin analogs in which the RK dipeptide unit was placed at positions 6-7, 10-11, or 14-15 adjacent to the parent RKs. Among these nociceptin analogs containing the RK triple repeat, [Arg-Lys(6-7)]- and [Arg-Lys(10-11)]nociceptins exhibited weak activities (6-9 and 60-90% of nociceptin, respectively) both in the receptor binding assay and in the [(35)S]GTPgammaS binding functional assay. In contrast, [Arg-Lys(14-15)]nociceptin was found to be very potent in both assays (3-fold in binding and 17-fold in GTPgammaS functional assay). [Arg-Lys(14-15)]nociceptin was the first peptide analog found to be stronger than the parent nociceptin, and structure-activity studies have suggested that the incorporated Arg-Lys(14-15) interacts with either the receptor acidic amino acid cluster or the receptor aromatic amino acid residues.     

Nociceptin receptor activation produces nitric oxide-mediated systemic hypotension

The purpose of the present study was to investigate the effects of L-N5-(1-iminoethyl)ornithine hydrochloride (L-NIO), an inhibitor of nitric oxide (NO) formation, and [Phe1-psi(CH2NH)-Gly2]Nociceptin(1-13)-NH2 (Phe-NOC), a nociceptin receptor antagonist, on the systemic vasodepressor response to nociceptin in the anesthetized rat. The systemic vasodepressor response to bolus intravenous (i.v.) injections of nociceptin was significantly reduced by L-NIO and Phe-NOC. The present data suggest activation of nociceptin receptors dilates the systemic vascular bed through a NO-dependent pathway. These data also demonstrate Phe-NOC is an efficacious and selective nociceptin receptor antagonist in vivo.