Tachykinin Receptor Antagonists Research Articles

Microbial Synthesis of Three Metabolites of a Tachykinin Receptor Antagonist, TAK-637.

The compound TAK-637 ((aR,9R)-7-[3,5-bis(trifluoromethyl)benzyl]-8,9,10,11-tetrahydro-9-methyl-5-(4-methylphenyl)-7H-[1,4]diazocino[2,1-g][1,7]naphthyridine-6,13-dione), a tachykinin receptor antagonist, has been shown to be converted into three metabolites in rats and guinea pigs. It was difficult to isolate the metabolites from rats and guinea pigs administered TAK-637 and elucidate the structures. A total of 100 actinomycete strains were screened for the ability to convert TAK-637 into its metabolites. Three strains, Streptomyces subrutilus IFO13388, Streptomyces tanashiensis subsp. cephalomyceticus IFO13929 and Streptomyces lavenduligriseus IFO13405, were found to convert TAK-637 into the metabolites consistent with the metabolites formed in rats and guinea pigs as determined by HPLC analyses. The metabolites were synthesized by microbial conversion using the actinomycetes. The structures of the metabolites were elucidated by spectral analyses. It was found that the methyl group at the C(5)-phenyl group of TAK-637 was hydroxylated and the resulting alcohol was converted to carboxylic acid via aldehyde. One of the metabolites (hydroxylated TAK-637) was obtained using a 200-l fermentor in a large-scale cultivation to evaluate its biological activity.

Microbial synthesis of three metabolites of a tachykinin receptor antagonist, TAK-637

The compound TAK-637 (( aR,9R)-7-[3,5-bis(trifluoromethyl)benzyl]-8,9,10,11-tetrahydro-9-methyl-5-(4-methylphenyl)- 7H-[1,4]diazocino[2,1- g][1,7]naphthyridine-6,13-dione), a tachykinin receptor antagonist, has been shown to be converted into three metabolites in rats and guinea pigs. It was difficult to isolate the metabolites from rats and guinea pigs administered TAK-637 and elucidate the structures. A total of 100 actinomycete strains were screened for the ability to convert TAK-637 into its metabolites. Three strains, Streptomyces subrutilus IFO13388, Streptomyces tanashiensis subsp. cephalomyceticus IFO13929 and Streptomyces lavenduligriseus IFO13405, were found to convert TAK-637 into the metabolites consistent with the metabolites formed in rats and guinea pigs as determined by HPLC analyses. The metabolites were synthesized by microbial conversion using the actinomycetes. The structures of the metabolites were elucidated by spectral analyses. It was found that the methyl group at the C (5)-phenyl group of TAK-637 was hydroxylated and the resulting alcohol was converted to carboxylic acid via aldehyde. One of the metabolites (hydroxylated TAK-637) was obtained using a 200- l fermentor in a large-scale cultivation to evaluate its biological activity.

Cooperation of NMDA and tachykinin NK 1 and NK 2 receptors in the medullary transmission of vagal afferent input from the acid-threatened rat stomach

Noxious challenge of the rat gastric mucosa by hydrochloric acid (HCl) is signaled to the nucleus tractus solitarii (NTS) and area postrema (AP). This study examined the participation of glutamate and tachykinins in the medullary transmission process. Activation of neurons was visualized by in situ hybridization autoradiography of c- fos messenger RNA (mRNA) 45 min after intragastric (IG) administration of 0.5 M HCl or saline. IG HCl caused many neurons in the NTS and some neurons in the AP to express c- fos mRNA. The NMDA glutamate receptor antagonist MK-801 (2 mg/kg), the NK 1 tachykinin receptor antagonist GR-205,171 (3 mg/kg) and the NK 2 receptor antagonist SR-144,190 (0.1 mg/kg) failed to significantly reduce the NTS response to IG HCl, whereas the triple combination of MK-801, GR-205,171 and SR-144,190 inhibited it by 45–50%. Only in rats that had been preexposed IG to HCl 48 h before the experiment was MK-801 alone able to depress the NTS response to IG HCl. In contrast, the c- fos mRNA response in the AP was significantly augmented by MK-801, an action that was prevented by coadministration of GR-205,171 plus SR-144,190. Inhibition of neuronal nitric oxide synthase with 7-nitroindazole (45 mg/kg) was without effect on the IG HCl-evoked c- fos mRNA expression in the NTS and AP. Our data show that glutamate acting via NMDA receptors and tachykinins acting via NK 1 and NK 2 receptors cooperate in the vagal afferent input from the acid-threatened stomach to the NTS and participate in the processing of afferent input to the AP in a different and complex manner. These opposing interactions in the AP and NTS and the increase in NMDA receptor function in the NTS after a gastric acid insult are likely to have a bearing on the neuropharmacology of dyspepsia.

A family of depsi-peptide fungal metabolites, as selective and competitive human tachykinin receptor (NK2) antagonists: fermentation, isolation, physico-chemical properties, and biological activity.

Four tachykinin (NK2) receptor inhibitors, SCH 378161 (1), SCH 217048 (2), SCH 378199 (3), and SCH 378167 (4) were isolated from the fermentation broth of a taxonomically unidentified fungus. These compounds were separated from the fermentation broth by ethyl acetate extraction. Purification and separation of the individual compounds were achieved by NK2 assay-guided fractionation using gel filtration, reverse phase chromatography and HPLC. They were identified to be a family of depsipeptides by spectroscopic and degradation studies. Compounds 1 and 3 contain proline and differ as an amide and acid whereas 2 and 4 contain pipecolic acid and differ in being an amide and acid. All of these compounds contain an identical hydroxy acid. They are selective NK2 inhibitors with Ki values ranging from 27-982 nM and demonstrate no activity at 10 microM in the NK1 and NK3 assays. In addition, compounds 1 and 2 inhibited NKA-induced increases in the concentration of intracellular Ca2+, [Ca2+]i, in a CHO cell expressing the human NK2 receptor; this inhibition was competitive in nature with pA2 values of 7.2 and 7.5, respectively. These data demonstrate that these natural products are selective and competitive receptor antagonists of the human NK2 receptor.

Projection Neurons with Shared Cotransmitters Elicit Different Motor Patterns from the Same Neural Circuit

Specificity in the actions of different modulatory neurons is often attributed to their having distinct cotransmitter complements. We are assessing the validity of this hypothesis with the stomatogastric nervous system of the crab Cancer borealis. In this nervous system, the stomatogastric ganglion (STG) contains a multifunctional network that generates the gastric mill and pyloric rhythms. Two identified projection neurons [modulatory proctolin neuron (MPN) and modulatory commissural neuron 1 (MCN1)] that innervate the STG and modulate these rhythms contain GABA and the pentapeptide proctolin, but only MCN1 contains Cancer borealis tachykinin-related peptide (CabTRP Ia). Selective activation of each projection neuron elicits different rhythms from the STG. MPN elicits only a pyloric rhythm, whereas MCN1 elicits a distinct pyloric rhythm as well as a gastric mill rhythm. We tested the degree to which CabTRP Ia distinguishes the actions of MCN1 and MPN. To this end, we used the tachykinin receptor antagonist Spantide I to eliminate the actions of CabTRP Ia. With Spantide I present, MCN1 no longer elicited the gastric mill rhythm and the resulting pyloric rhythm was changed. Although this rhythm was more similar to the MPN-elicited pyloric rhythm, these rhythms remained different. Thus, CabTRP Ia partially confers the differences in rhythm generation resulting from MPN versus MCN1 activation. This result suggests that different projection neurons may use the same cotransmitters differently to elicit distinct pyloric rhythms. It also supports the hypothesis that different projection neurons use a combination of strategies, including using distinct cotransmitter complements, to elicit different outputs from the same neuronal network.

Effects of tachykinin receptor agonists and antagonists on the guinea-pig isolated oesophagus.

1. Vagal nerve stimulation of the guinea-pig isolated oesophagus produced a triphasic tetrodotoxin (TTX)-sensitive contractile response. The third phase, which was resistant to ganglion blocking drugs, was selectively abolished by capsaicin, suggesting the involvement of one or more neuropeptides released from afferent neurons. Receptors on cholinergic neurons were subsequently activated because the response was atropine sensitive. Contractile responses resulting from exogenous substance P were abolished by atropine and TTX and enhanced by physostigmine. These findings suggest that the third phase may be mediated by the action of a substance P-like neuropeptide released from sensory nerve endings that subsequently activated cholinergic neurons. 2. The tachykinin receptors in the body of the guinea-pig oesophagus were characterized by determining the relative agonist potencies of natural tachykinins as well as tachykinin receptor-selective analogues. Antagonist affinities were also determined. The results indicated the presence of both NK2 and NK3 receptors. In addition, the effects of a cocktail of peptidase inhibitors (captopril, thiorphan and amastatin) on responses to various tachykinins and synthetic analogues were determined. The results indicate that one or more peptidases are present in this preparation. 3. Experiments using various tachykinin receptor antagonists were performed to determine whether the activation of tachykinin receptors played a role in the mediation of the third phase of the response to vagal nerve stimulation. While this response was unaffected by NK1 and NK2 receptor-selective antagonists, it was only partially inhibited (23%) by the NK3 receptor antagonist SR 142801. Thus, in the guinea-pig oesophagus, it appears that NK3 receptors play only a minor role in mediating a contractile response when afferent neurons are excited by vagal nerve stimulation.

Hemokinin is a hematopoietic-specific tachykinin that regulates B lymphopoiesis.

We report here the molecular cloning of a newly identified preprotachykinin gene, Pptc, which specifies the sequence for a new preprotachykinin protein and bioactive peptide designated hemokinin 1 (HK-1). PPT-C mRNA was detected primarily in hematopoietic cells in contrast to the previously described Ppta and Pptb genes, which are predominantly expressed in neuronal tissues. HK-1 has several biological activities that are similar to the most studied tachykinin, substance P, such as induction of plasma extravasation and mast cell degranulation. However, HK-1 also has properties that are indicative of a critical role in mouse B cell development. HK-1 stimulated the proliferation of interleukin 7-expanded B cell precursors, whereas substance P had no effect. HK-1, but not substance P, promoted the survival of freshly isolated bone marrow B lineage cells or cultured, lipopolysaccharide-stimulated pre-B cells. N-acetyl-L-trytophan-3,5-bistrifluromethyl benzyl ester, a tachykinin receptor antagonist, increased apoptosis of these cells and in vivo administration of this antagonist led to specific reductions of the B220lowCD43 population (the pre-B cell compartment) in the bone marrow and the IgMhighIgDlow population (the newly generated B cells) in the spleen. Thus, HK-1 may be an autocrine factor that is important for the survival of B cell precursors at a critical phase of development.

Role of substance P and tachykinin receptor antagonists in citric acid-induced cough in pigs

The purpose of this work was to investigate the role of tachykinins in cough induced by citric acid (0.8 M) in pigs. With this object, we have studied the effect of citric acid on substance P content in the tracheo-bronchial tree and the effects of substance P and of tachykinin receptor antagonists on citric acid-induced cough. Citric acid exposure significantly increased substance P concentration in both broncho-alveolar and tracheal lavage fluids, while it decreased significantly the substance P content in tracheal mucosa. Substance P did not elicit cough, but significantly potentiated the citric acid-induced cough frequency. Tachykinin NK 1, NK 2 or NK 3 receptor antagonists, SR 140333 (nolpitantium), SR 48968 (saredutant) and SR 142801 (osanetant), respectively, significantly inhibited citric acid-induced cough. The same inhibitory effect of tachykinin receptor antagonists was observed, when substance P was nebulised before citric acid challenge. We conclude that citric acid induces in pigs a release of substance P in the tracheo-bronchial tree, which plays a sensitising role on the cough reflex. The involvement of tachykinin NK 1, NK 2, NK 3 receptors are also demonstrated in this reflex.

Peripheral actions of tachykinins

Tachykinins mediate a variety of physiological processes in the gastrointestinal, pulmonary and genito-urinary tract mainly through the stimulation of NK1 and NK2 receptors. Preclinical evidence obtained through the use of selective tachykinin receptor antagonists indicates that endogenous tachykinins are involved in augmented smooth muscle contraction, vasodilatation, chemotaxis and activation of immune cells, mucus secretion, water absorption/secretion. Recent evidence also suggests that endogenous tachykinins released at the peripheral level may play a role in visceral inflammation, hyperreflexia and hyperalgesia. Possible mechanisms underlying the stimulation of primary afferent neurons by tachykinins may involve a direct excitation of these neurons and the release of mediators which sensitise or stimulate sensory nerves. Tachykinin receptor antagonists could have a clinical utility in several human diseases such as irritable bowel syndrome, asthma, and in micturition disturbances characterized by a hyperactive bladder.

Correolide, a nor-triterpenoid blocker of Shaker-type Kv1 channels elicits twitches in guinea-pig ileum by stimulating the enteric nervous system and enhancing neurotransmitter release.

Correolide (1 - 10 microM), a nortriterpene purified from Spachea correae and a selective blocker of Kv1 potassium channels, elicits repetitive twitching in guinea-pig ileum. This effect is not seen in guinea-pig duodenum, portal vein, urinary bladder or uterine strips, nor in rat or mouse ileum. The time course and amplitude of the correolide-induced twitches in guinea-pig ileum are similar to those elicited by electrical stimulation of the enteric nervous system. The correolide-induced twitching is not affected by pre-treatment with capsaicin (1 microM), but is facilitated by the NO synthase inhibitor, N(G)-nitro-L-arginine methyl esther (L-NAME, 200 microM). The correolide-induced twitching is abolished by tetrodotoxin (1 microM) or hexamethonium (100 microM), and is markedly inhibited by nifedipine (0.3 microM) or atropine (0.2 microM). The atropine-resistant component is inhibited by selective antagonists of NK1 and NK2 tachykinin receptors, namely GR 82334 and GR 94800 (1 microM each). The former compound is more effective in inhibiting the correolide-induced, atropine-resistant activity. Correolide intensified the twitching of ileum segments exposed to saturating concentrations of margatoxin (MgTX), which suggests that Kv1 sub-types other than Kv1.1 (Kv1.4 or Kv1.5) are involved in the relatively greater degree of stimulation of the enteric nervous system by correolide, as compared to MgTX. We propose that blockade of Kv1 channels by correolide increases the excitability of intramural nerve plexuses promoting release of acetylcholine and tachykinins from excitatory motor neurons. This, in turn, leads to Ca(2+)-dependent action potentials and twitching of the muscle fibres.

Combined tachykinin receptor antagonist: synthesis and stereochemical structure–activity relationships of novel morpholine analogues

We report herein the synthesis and stereochemical structure–activity relationships of novel morpholine analogues 12 and 13 with regards to NK 1, NK 2 and NK 3 tachykinin receptor binding affinity. An essential requirement for more potent binding affinities was controlled by absolute configuration. ( S,R)- 12 and ( S,R)- 13 exhibited high binding affinities for NK 1, NK 2 and NK 3 receptors.

Evidence for an involvement of tachykinins in allodynia in streptozocin-induced diabetic rats

A better knowledge of the pathophysiology of chronic pain could help to improve the treatment of patients with such syndrome. The aim of the present work was to elucidate the possible involvement of spinal substance P and neurokinin A in the mechanical and thermal allodynia observed in streptozocin-induced diabetic rats. A tachykinin NK 1 receptor antagonist, RP-67,580 ((3aR,7aR) -7,7-diphenyl-2-(1-imino-2(2-methoxy phenyl)-ethyl) perhydroisoindol-4-one hydrochloride), a tachykinin NK 2 receptor antagonist, SR-48,968 (( S)- N-methyl (4-(acetylamino-4phenylpiperidino)-2-(3, 4-dichlorophenyl) butyl) benzamide) and their respective enantiomers were intrathecally administered 4 weeks after the induction of diabetes. Mechanical and thermal allodynia were evaluated before and up to 60 min after injection. The tachykinin receptor antagonists at the highest doses (10 and 25 μg) significantly reduced allodynia, their enantiomers being inactive. Both of these data suggest the involvement of substance P and neurokinin A in the neuropathy-induced allodynia and offer a novel hypothesis to treat chronic pain due to diabetes.

Neural mechanisms in asthma

Advances in the understanding of neural mechanisms in asthma may provide novel therapeutic approaches in the treatment of asthma. Excessive activity of cholinergic nerves may be important in asthma. Dysfunction of M2 muscarinic receptors in asthma may lead to excessive bronchoconstriction and mucus secretion and can be induced in animal models by a range of stimuli including allergen, viral infection, ozone, eosinophil products and cytokines. Cholinergic mechanisms may be especially important in certain types of patients and anticholinergic agents provide protection against bronchospasm due to psychogenic factors or beta2-blockers. Non-adrenergic non-cholinergic (NANC) mechanisms, both inhibitory (i-NANC) and excitatory (e-NANC), may play a significant role in the pathophysiology of asthma. The putative neurotransmitters, vasoactive interstinal polypeptide (VIP) and nitric oxide (NO), mediate neural bronchodilation in human airways. There does not appear to be a defect in the i-NANC system in moderate or severe asthma. e-NANC is mediated by the sensory neuropeptides substance P (SP) and the more potent bronchoconstrictor neurokinin A (NKA). Various studies suggest that the SP content of human airways is increased in asthma. Tachykinins are not only present in sensory nerves, but also are produced by inflammatory cells such as alveolar macrophages, dendritic cells, eosinophils, lymphocytes and neutrophils. They can be released into the airways by stimuli such as allergen and ozone. Evidence suggests that in addition to smooth muscle contraction, which is mediated mainly by NK2 receptors, tachykinins also cause mucus secretion, plasma extravasation and stimulate inflammatory and immune cells. These effects are mediated by NK1 receptors. Recent studies have shown that NK2 receptor antagonists such as saredutant partially inhibit NKA-induced bronchoconstriction in asthmatics. Thus, tachykinin receptor antagonists have potential as therapies for asthma.

Effects of TAK-637, a tachykinin receptor antagonist, on the micturition reflex in guinea pigs

The effects of a new tachykinin NK 1 receptor antagonist, ( aR,9 R)-7-[3,5-bis(trifluoromethyl)benzyl]-8,9,10,11-tetrahydro-9-methyl-5-(4-methylphenyl)-7 H-[1,4]diazocino[2,1- g][1,7]naphthyridine-6,13-dione (TAK-637), on the micturition reflex were compared with those of drugs used for abnormally frequent micturition or incontinence. TAK-637 showed a characteristic effect on the distension-induced rhythmic bladder contractions in guinea pigs. The systemic administration of TAK-637 decreased the number but not the amplitude of the distension-induced rhythmic bladder contractions. A similar effect was observed in animals in which the spinal cord had been severed. TAK-637 also inhibited the micturition reflex induced by topical application of capsaicin onto the surface of bladder dome. From these results, it is concluded that TAK-637 inhibits sensory transmissions from the bladder evoked by both physiological and nociceptive stimuli by blocking tachykinin NK 1 receptors, possibly at the level of the spinal cord. On the other hand, the other drugs such as oxybutynin, tolterodine, propiverine, and inaperisone showed no effects on the frequency of the distension-induced rhythmic bladder contractions but decreased the contraction amplitude. Therefore, TAK-637 may represent a new class of drugs, which would be effective for abnormally frequent micturition without causing voiding difficulties due to decreased voiding pressure.

Inhibitory effect of PACAP(6-38) on relaxations induced by PACAP, VIP and non-adrenergic, non-cholinergic nerve stimulation in the guinea-pig taenia caeci.

The effect of the pituitary adenylate cyclase activating polypeptide (PACAP) receptor antagonist PACAP(6-38) on the relaxant response to exogenous PACAP, vasoactive intestinal polypeptide (VIP) and nonadrenergic, non-cholinergic (NANC) nerve stimulation was tested in the guinea-pig taenia caeci, in the presence of atropine (10(-6) M) and guanethidine (3x10(-6) M). PACAP(6-38) (3x10(-6) M) strongly inhibited sub-maximal relaxations evoked by exogenous PACAP (1-3x 10(-8) M) or VIP (10(-8) M), but not those due to isoprenaline (4-8x10(-8) M) or ATP (10(-6) M). PACAP(6-38) caused a small but significant (approximately 20%) inhibition of the NANC relaxation due to electrical field stimulation (1 Hz or 10 Hz for 20 s). At these frequencies PACAP(6-38) caused no inhibition of the NANC relaxation in the presence of the P2 purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS; 5x10(-5) M), or PPADS plus the NO-synthase blocker NG-nitro-L-arginine (L-NOARG; 10(-4) M); in preparations pretreated with L-NOARG (10(-4) M) alone PACAP(6-38) retained its inhibitory effect. The PPADS- and L-NOARG-resistant NANC relaxation with 10 Hz electrical stimulation was blocked by apamin (10(-7) M); it was not significantly modified by the tachykinin receptor antagonist spantide (10(-5) M). Tachyphylaxis to PACAP(1-27) (10(-7) M for 10 min) strongly inhibited the relaxation due to PACAP(1-38) (1-3x10(-8) M) and reduced electrical stimulation-evoked relaxations by half. The putative VIP antagonist VIP(10-28) (10(-5) M) failed to significantly reduce the relaxant action of exogenous VIP (1-3x10(-8) M). Relaxation induced by PACAP(1-38) (1-2x10(-8) M) was not influenced by a mixture of PPADS (5x10(-5) M) and L-NOARG (10(-4) M). It is concluded that: (a) PACAP(6-38) is a VIP/PACAP antagonist in the guinea-pig taenia caeci; (b) a release of a VIP/PACAP-like substance from enteric nerves is involved in the NANC relaxation in this preparation, but its contribution is relatively small and seems to depend on the functional integrity of the PPADS-sensitive inhibitory mechanism; (c) the PPADS- plus L-NOARG-resistant NANC relaxation probably involves apamin-sensitive K+ channels.

Role of tachykinins in asthma.

The sensory neuropeptides substance P (SP) and neurokinin A (NKA) are localized to sensory airway nerves, from which they can be released by a variety of stimuli, including allergen, ozone, or inflammatory mediators. Sensory nerves containing these peptides are relatively scarce in human airways, but it is becoming increasingly evident that inflammatory cells such as eosinophils, macrophages, lymphocytes, and dendritic cells can produce the tachykinins SP and NKA. Moreover, immune stimuli can boost the production and secretion of SP and NKA. SP and NKA have potent effects on bronchomotor tone, airway secretions, and bronchial circulation (vasodilation and microvascular leakage) and on inflammatory and immune cells. Following their release, tachykinins are degraded by neutral endopeptidase (NEP) and angiotensin-converting enzyme. The airway effects of the tachykinins are largely mediated by tachykinin NK1 and NK2 receptors. Tachykinins contract smooth muscle mainly by interaction with NK2 receptors, while the vascular and proinflammatory effects are mediated by the NK1 receptor. In view of their potent effects on the airways, tachykinins have been put forward as possible mediators of asthma, and tachykinin receptor antagonists are a potential new class of antiasthmatic medication.

Tachykinins in the porcine pancreas: potent exocrine and endocrine effects via NK-1 receptors.

The localization, release, and effects of substance P and neurokinin A were studied in the porcine pancreas and the localization of substance P immunoreactive nerve fibers was examined by immunohistochemistry. The effects of electrical vagus stimulation and capsaicin infusion on tachykinin release and the effects of substance P and neurokinin A infusion on insulin, glucagon, somatostatin, and exocrine secretion were studied using the isolated perfused porcine pancreas with intact vagal innervation. NK-1 and NK-2 receptor antagonists were used to investigate receptor involvement. Substance P immunoreactive nerve fibers were localized to islets of Langerhans, acini, ducts, and blood vessels. Vagus stimulation had no effect on substance P and neurokinin A release, whereas capsaicin infusion stimulated release of both. Substance P and neurokinin A infusion increased release of insulin, glucagon, and exocrine secretion, whereas somatostatin secretion was unaffected. The effect of substance P on insulin, glucagon, and exocrine secretion was blocked by the NK-1 receptor antagonist. The effect of electrical stimulation of vagus nerves on insulin and exocrine secretion was not influenced by tachykinin receptor antagonists. We conclude that tachykinins stimulate both endocrine and exocrine pancreatic functions through NK-1 receptors. Tachykinins are not involved in vagal regulation of pancreatic secretion in pigs but could constitute part of an alternative stimulatory system.

Pro-inflammatory effects of substance P: new perspectives for the treatment of airway diseases?

Non-adrenergic, non-cholinergic (i.e. NANC) neuronal transmission has been implicated in the pathophysiology of asthma. Attention has focused on both inhibitory NANC transmission mediated by its putative neurotransmitters vasoactive intestinal peptide (VIP) and nitric oxide (NO) and excitatory NANC transmission mediated by the sensory neuropeptides. Studies on rodent airway and non-airway tissue have demonstrated that activation of non-cholinergic excitatory nerves by mechanical or chemical stimuli can generate local axon reflexes that lead to bronchoconstriction and neurogenic inflammation. The sensory neuropeptides substance P (SP) and neurokinin A (NKA) have various effects that could contribute to changes observed in asthmatic airways, including smooth muscle contraction, submucosal gland secretion, vasodilatation, an increase in vascular permeability, stimulation of cholinergic nerves and stimulation of immune cells 1 Bertrand C. Geppetti P. Tachykinin and kinin receptor antagonists: therapeutic perspectives in allergic airway disease. Trends Pharmacol. Sci. 1996; 17: 255-259 Abstract Full Text PDF PubMed Scopus (81) Google Scholar , 2 Joos G.F. et al. Sensory neuropeptides and the human lower airways: present state and future directions. Eur. Respir. J. 1994; 7: 1161-1171 PubMed Google Scholar . Most of these effects have been observed in both human and animal tissue and are mediated by specific tachykinin receptors; stimulation of the NK2 receptor mediates a major part of the tachykinin-induced airway smooth muscle contraction, whereas stimulation of NK1 receptors induces vasodilatation, plasma protein extravasation, mucus secretion and stimulation of inflammatory and immune cells 3 Advenier C. et al. Role of tachykinins as contractile agonists of human airways in asthma. Clin. Exp. Allergy. 1999; 29: 579-584 Crossref PubMed Scopus (31) Google Scholar . The effects of tachykinins on the airways can be terminated by enzymatic degradation, mainly by the action of the ectoenzyme neutral endopeptidase 2 Joos G.F. et al. Sensory neuropeptides and the human lower airways: present state and future directions. Eur. Respir. J. 1994; 7: 1161-1171 PubMed Google Scholar . (2s-cis)-2-(diphenylmethyl)-N-[(2-methoxyphenyl)methyl]-1-azabicyclo[2.2.2]octan-3-amine ((+)-(2s,3s)-3-methoxybenzyl amino)-2-phenylpiperidine N-[N2-[N-[N-[N-[2,3-didehydro-N-methyl-N-[N-[3-(2-pentylphenyl)-propionyl]-l-threonyl]tyrosyl-l-leucynyl]-d-phenylalanyl]-l-allothreonyl]-l-asparaginyl]-l-serine-n-lactone] N2-[(4r)-4-hydroxy-1-(1-methyl-1H-indol-3-yl)carbonyl-l-prolyl]-N-phenylmethyl-3-(2-naphthyl)-l-alaninamide (s)-N-methyl-N[4-(4-acetylamino-4-phenyl piperidino)-2-(3,4-dichlorophenyl)butyl] benzamide

A versatile method for the preparation of 2,2-disubstituted morpholine analogues

We describe a versatile synthetic method for the preparation of 2,2-disubstituted morpholine analogues. Iodoetherification of 1,1-disubstituted olefin with N-Boc-aminoethanol using NIS proceeded smoothly in a regioselective manner and the following cyclization was accomplished in good yield. We successfully applied this method for the preparation of the key intermediate 2 of tachykinin receptor antagonist.

Evidence for the involvement of ATP, but not of VIP/PACAP or nitric oxide, in the excitatory effect of capsaicin in the small intestine

The contractile effect of capsaicin in the guinea-pig small intestine involves an activation of enteric cholinergic neurons. Our present data show that the P 2 purinoceptor antagonist pyridoxal-phosphate-6-azophenyl-2′,4′-disulphonic acid (PPADS, 30 μM) significantly reduces the contractile response to capsaicin (2 μM) in the presence, but not in the absence, of the tachykinin receptor antagonists [O-Pro 9, (Spiro-γ-lactam)Leu 10, Trp 11]physalaemin (1–11) (GR 82334; 3 μM) and ( S)-( N)-(1-(3-(1-benzoyl-3-(3,4-dichlorophenyl)piperidin-3-yl)propyl)-4-phenylpiperidine-4-yl)- N-methylacetamide (SR 142801; 100 nM) (for blocking tachykinin NK 1 and NK 3 receptors, respectively). PPADS (30 μM) fails to influence submaximal cholinergic contractions evoked by cholecystokinin octapeptide (CCK-8; 2–3 nM) or senktide (1 nM), or the direct smooth muscle-contracting effect of histamine (100–200 nM). A higher concentration (300 μM) of PPADS is also without effect against the stimulatory action of cholecystokinin octapeptide. This means that PPADS can probably be safely used as a purinoceptor antagonist in intestinal preparations. The putative pituitary adenylate cyclase activating peptide (PACAP) receptor antagonist PACAP-(6–38) (3 μM) significantly reduces the contractile effect of PACAP-(1–38) (10 nM) and abolishes that of vasoactive intestinal polypeptide (VIP; 10 nM). PACAP-(6–38) (3 μM) fails to influence the effect of capsaicin (2 μM) both in the absence and in the presence of tachykinin receptor antagonists. The nitric oxide (NO) synthase inhibitor N G-nitro- l-arginine ( l-NOARG; 100 μM) also fails to inhibit the capsaicin-induced motor response. We conclude that an endogenous ligand of PPADS-sensitive P 2 purinoceptors (possibly ATP), but not a VIP/PACAP-like peptide or NO, is involved in the nontachykininergic activation of cholinergic neurons in the course of the capsaicin-induced contraction.