Cigarette smoke increases mucosal permeability in guinea pig trachea via tachykinin NK2 receptor activation

We investigated whether exposure to cigarette smoke increases the mucosal permeability in guinea pig trachea and if this effect could be mediated by tachykinin NK2 receptor activation. Guinea pigs were exposed to either three different doses of cigarette smoke or room air. Mucosal permeability was measured by monitoring the rate of appearance in the circulation of horseradish peroxidase (HRP) that had been instilled into the isolated tracheal segment. Exposure to 20 and 30 puffs but not 10 puffs of cigarette smoke increased the tracheal mucosal permeability. Pretreatment with the tachykinin NK2 receptor antagonist SR48,968 [(S)-N-methyl-N[4-(4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl)butyl]benzamide] completely inhibited the increase in the permeability of the tracheal mucosa induced by exposure to cigarette smoke, whereas the tachykinin NK1 receptor antagonist SSR240,600 [(R)-2-(1-{2-[4-{2-[3,5-bis(trifluoromethyl)phenyl]acetyl}-2-(3,4-dichlorophenyl)-2-morpholinyl]ethyl}-4-piperidinyl)-2-methylpropanamide] and the tachykinin NK3 receptor antagonist SR142,801 [(S)-(N)-(1-[3-(1-benzoyl-3(3,4-dichlorophenyl)piperidine-3-yl)propyl]-4-phenylpiperidin-4-yl)-N-methyl-acetamide] had no effect. It is concluded that endogenous tachykinins via NK2 receptor activation mediate the increase in the permeability of the tracheal mucosa induced by exposure to cigarette smoke in guinea pigs.     

Tachykinin NK2 receptor antagonists. A patent review (2006 - 2010)

INTRODUCTION: Tachykinins are endogenous peptide neurotransmitters, acting through the NK1, NK2 and NK3 receptors, at central and peripheral level. At peripheral level, they are involved in contraction of smooth muscle, secretion of water and ion from epithelia, as well as modulation of visceral pain sensitivity. Tachykinin NK2 receptor antagonists have the potential to be useful in the treatment of various gastrointestinal, genitourinary and CNS diseases. AREAS COVERED: In this review, an overview of the patenting activity in the last 5 years is provided. Patents from different companies and research groups are discussed for their novelty and evaluated in relation to proposed indications and clinical studies. Relevant biological data are also presented. Patents claiming new therapeutic indications are included in a dedicated section. EXPERT OPINION: Although there is still no tachykinin NK2 receptor antagonist approved for use in human therapy, research in the field is still proposing new compounds and possible uses. A number of candidates are being evaluated in Phase II clinical studies, in indications ranging from gastrointestinal disorders to inflammatory diseases. The results of these studies will indicate the role of tachykinin NK2 receptor antagonists in human therapy.     

Tachykinin NK(2) receptor mediates contraction and ion transport in rat colon by different mechanisms

We have characterized the tachykinin NK(2) receptor-mediated contraction and vectorial ion transport responses in the muscularis mucosae and mucosa of the rat isolated distal colon, respectively. The tachykinin NK(2) receptor-selective antagonist nepadutant (c([(beta-D-GlcNAc)Asn-Asp-Trp-Phe-Dpr-Leu]c(2beta-5beta))) produced competitive antagonism of [betaAla(8)]neurokinin A-(4-10)-induced contraction (pK(B) = 9.3) in the muscularis mucosae, and insurmountable blockade of increases in short-circuit current (I(sc)) responses (pK(B) = 8.6) in the mucosa. However, this latter effect was completely reversed by washout of the antagonist. [betaAla(8)]Neurokinin A-(4-10)-induced contractions were unaffected by indomethacin (3 microM). In sharp contrast, I(sc) responses induced by [betaAla(8)]neurokinin A-(4-10) (100 nM) were inhibited (>70%) by indomethacin (3 microM), while I(sc) responses to substance P (3 microM) were unchanged. Our study provides the first evidence that in the same organ stimulation of tachykinin NK(2) receptors leads to two independent responses mediated by different effector mechanisms both of which are blocked (albeit with different kinetics) by the potent and selective tachykinin NK(2) receptor antagonist, nepadutant.     

Tachykinin NK2 receptor antagonists for the treatment of irritable bowel syndrome

Tachykinin NK2 receptors are expressed in the gastrointestinal tract of both laboratory animals and humans. Experimental data indicate a role for these receptors in the regulation of intestinal motor functions (both excitatory and inhibitory), secretions, inflammation and visceral sensitivity. In particular, NK2 receptor stimulation inhibits intestinal motility by activating sympathetic extrinsic pathways or NANC intramural inhibitory components, whereas a modulatory effect on cholinergic nerves or a direct effect on smooth muscle account for the NK2 receptor-mediated increase in intestinal motility. Accordingly, selective NK2 receptor antagonists can reactivate inhibited motility or decrease inflammation- or stress-associated hypermotility. Intraluminal secretion of water is increased by NK2 receptor agonists via a direct effect on epithelial cells, and this mechanism is active in models of diarrhoea since selective antagonists reverse the increase in faecal water content in these models. Hyperalgesia in response to intraluminal volume signals is possibly mediated through the stimulation of NK2 receptors located on peripheral branches of primary afferent neurones. NK2 receptor antagonists reduce the hyper-responsiveness that occurs following intestinal inflammation or application of stressful stimuli to animals. Likewise, NK2 receptor antagonists reduce intestinal tissue damage induced by chemical irritation of the intestinal wall or lumen. In healthy volunteers, the selective NK2 antagonist nepadutant reduced the motility-stimulating effects and irritable bowel syndrome-like symptoms triggered by intravenous infusion of neurokinin A, and displayed other characteristics that could support its use in patients. It is concluded that blockade of peripheral tachykinin NK2 receptors should be considered as a viable mechanism for decreasing the painful symptoms and altered bowel habits of irritable bowel syndrome patients.     

Tachykinin NK1 but not NK2 receptors mediate non-cholinergic excitatory junction potentials in the circular muscle of guinea-pig colon.

1. The effect of tachykinin NK1 and NK2 receptor antagonists on noncholinergic excitatory junction potentials (e.j.ps) evoked by electric field stimulation (EFS) in the circular muscle of the guinea-pig proximal colon was investigated by means of a sucrose-gap technique. 2. In the presence of 1 microM atropine, submaximal EFS (10 Hz, 20-30 V, 0.5 ms pulse width, 1 s train duration) evoked an inhibitory junction potential (i.j.p.) followed by e.j.p. with superimposed action potentials (APs) and contraction. Addition of either NG-nitro-L-arginine (L-NOARG, 0.1 mM) or apamin (0.1 microM) inhibited the evoked i.j.p. and the combined administration of the two agents almost abolished it. In the presence of both L-NOARG and apamin, an atropine-resistant e.j.p. was the only electrical response evoked by EFS in 50% of cases and a small i.j.p. (10% of original amplitude) followed by e.j.p. was evident in the remainder. 3. In the presence of L-NOARG and apamin, the tachykinin NK1 receptor antagonists, (+/-)-CP 96,345 and GR 82,334 (10 nM-3 microM) concentration-dependently inhibited the atropine-resistant e.j.p. and accompanying contraction evoked by EFS. EC50 values were: 0.77 microM (e.j.p. inhibition) and 0.22 microM (inhibition of contraction) for (+/-)-CP 96,345; 0.61 microM (e.j.p. inhibition) and 0.20 microM (inhibition of contraction) for GR 82,334. The tachykinin NK2 receptor antagonists, MEN 10,376 (up to 3 microM) and SR 48,968 (up to 1 microM) had no effect on the atropine-resistant e.j.p. MEN 10,376 (3 microM) but not SR 48,968 produced a slight inhibition of the evoked contraction.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tachykinin NK(3) receptor agonists induced microvascular leakage hypersensitivity in the guinea-pig airways.

Microvascular leakage hypersensitivity is a main component of neurogenic inflammation and of tachykinin effects.The aim of this study was to examine the ability of neurokinin B and of the tachykinin NK(3) receptor agonists, [MePhe(7)]neurokinin B or senktide, to potentiate when given by aerosol the microvascular leakage induced by histamine in guinea-pig airways and to compare their effects to those of tachykinin NK(1) (substance P, [Sar(9),Met(O(2))(11)]substance P) or tachykinin NK(2) (neurokinin A, [betaAla(8)]neurokinin A (4-10)) receptor agonists. Guinea-pigs were pretreated successively for 10 min with aerolized salbutamol and phosphoramidon; 15 min later, they were exposed for 30 min to an aerosolized solution of tachykinin receptor agonists; 24 h later, the animals were anaesthetized and vascular permeability was quantified by extravasation of Evans blue dye. Neurokinin B, [MePhe(7)]neurokinin B and senktide (3 x 10(-6)-3 x 10(-5)M) induced a potentiation of the effects of histamine on the vascular permeability in the trachea and main bronchi. Compared to other tachykinin NK(1) and NK(2) receptor agonists, the order of potency was: senktide>neurokinin B=[Sar(9),Met(O(2))(11)]substance P=[betaAla(8)]neurokinin A (4-10)=[MePhe(7)]neurokinin B>neurokinin A>substance P. The potentiation by [MePhe(7)]neurokinin B of histamine-induced microvascular leakage was abolished by the tachykinin NK(1) receptor antagonist SR140333 ([(S)1-(2-[3-(3,4-dichlorophenyl)-1-(3-iso-propoxyphenylacetyl)piperidin-3-yl]etyl)-4-phenyl-1-azoniabicyclo[2.2.2]octane, chloride]) or the tachykinin NK(3) receptor antagonists SR 142801 ([(R)-(N)-(1-(3-(l-benzoyl-3-(3,4-dichlorophenyl)piperidin-3-yl) propyl)-4-phenylpiperidin-4-yl)-N-methylacetamide]) and SB 223412 ([(S)-(-)-N-(alpha-ethylbenzyl)-3-hydroxy-2-phenylquinoline-4-carboxamide]). In conclusion, these results suggest that tachykinin NK(3) receptors might be involved in the potentiation of histamine-induced increase in microvascular permeability.     

Tachykinin NK1 and NK2 receptors mediate inhibitory vs excitatory motor responses in human isolated corpus cavernosum and spongiosum

Motor effects produced by tachykinins were studied in human isolated corpus spongiosum and cavernosum. In quiescent preparations neurokinin A caused potent contractions (pD(2)=8.3 - 7.9 respectively) prevented by the NK(2) receptor-selective antagonist nepadutant, whereas [Sar(9)]SP sulfone and senktide (NK(1) and NK(3) receptor-selective agonists) produced no effect or spare contractions. In KCl-precontracted corpus spongiosum septide (pD(2)=7.1) and [Sar(9)]SP sulfone (pD(2)=7.7) produced tetrodotoxin-resistant relaxations, abolished by the tachykinin NK(1) receptor-selective antagonist SR 140333. [Sar(9)]SP sulfone (1 microM) produced similar relaxations in precontracted corpus cavernosum. Electrical field stimulation (EFS) elicited tetrodotoxin-sensitive relaxations, which were additive to those produced by [Sar(9)]SP sulfone. N(omega)-nitro-L-arginine (L-NOARG) totally prevented both [Sar(9)]SP sulfone- and EFS-induced relaxations. These results show that tachykinin NK(1) and NK(2) receptors mediate opposite motor effects in human penile tissues, suggesting a possible modulatory role of tachykinins on smooth muscle tone in these organs.     

Tachykinin NK(2) receptors facilitate acetylcholine release from guinea-pig isolated trachea

The release of newly synthesised [3H]acetylcholine was evoked by electrical field stimulation (5 Hz, 600 pulses) of epithelium-deprived guinea-pig trachea strips after sensory neuropeptides depletion with 3 microM capsaicin. The selective tachykinin NK(2) receptor agonist [betaAla(8)]neurokinin A-(4-10) increased in a concentration-dependent manner the electrically-induced release of [3H]acetylcholine. The facilitatory effect was antagonised by the selective non-peptide tachykinin NK(2) receptor antagonist, SR 48968 (apparent pK(B) 8.9). The tachykinin NK(1) and NK(3) receptor agonists substance P methyl ester and senktide (both 10 and 100 nM), respectively, did not affect the evoked release of [3H]acetylcholine. It is concluded that the cholinergic nerves of guinea-pig trachea are endowed with prejunctional facilitatory tachykinin receptors of the NK(2) subtype.     

Tachykinin NK1 receptor subtypes in the rat urinary bladder.

1. Following the recent proposal that the selective agonist septide, ([pGlu6,Pro9]SP(6-11)), acts on a novel tachykinin receptor distinct from the ''classical'' NK1 receptor, the aim of the study was to investigate the possible heterogeneity of tachykinin NK1 receptors in the rat urinary bladder. 2. The synthetic tachykinin receptor agonists, septide (pD2 7.87) and [Sar9]substance P (SP) sulphone (pD2 7.64) produced concentration-dependent contractions of the rat isolated urinary bladder. 3. The NK1 receptor antagonists GR82,334, (+/-)-CP96,345, and RP67,580 competitively antagonized (slopes of Schild plot not significantly different from unity) the response to septide with the rank order of potency (pKB values in parentheses): RP 67,580 (7.57) > GR 82,334 (7.01) > (+/-)-CP 96,345 (6.80). The same antagonists were significantly less potent when tested against [Sar9]SP sulphone, while maintaining the same rank order of potency: RP 67,580 (7.00) > GR 82,334 (5.93) > (+/-)-CP 96,345 (< 6). The antagonists did not affect the concentration-response curve to bombesin. 4. To exclude the involvement of the NK2 receptor, a second series of experiments was performed in the presence of the potent nonpeptide NK2 receptor antagonist, SR 48,968. SR 48,968 (1 microM) produced a rightward shift of the concentration-response curve to the NK2 receptor selective agonist, [beta Ala8]neurokinin A (NKA) (4-10). SR 48,968 did not significantly modify the response to SP, NKA, neurokinin B (NKB), neuropeptide K (NPK), neuropeptide gamma (NP gamma), SP(4-11), SP(6-11), septide or [Sar9]SP sulphone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Participation of neuropeptides in antigen-induced contraction of guinea pig bronchi via NK(2) but not NK(1) receptor stimulation

We evaluated the contribution of neuropeptides to antigen-induced contractions of isolated bronchi and tracheae of passively sensitized guinea pigs using CP-96345 and SR 48968, specific antagonists of NK(1) and NK(2) receptors, respectively, in combination with treatment by an antihistaminic and a cysteinyl leukotriene antagonist. SR-48968 but not CP-96345, significantly inhibited the late phase of the bronchial contraction. Phosphoramidon, a neutral endopeptidase inhibitor, tended to potentiate bronchial contraction. Posttreatment with SR-48968 decreased the enhanced contraction induced by the inhibitor as well as the nonenhanced contraction to similar levels of tension. On the other hand, antigen-induced tracheal contraction was not altered by either neuropeptide antagonist. These results suggest that neuropeptides mediate the antigen-induced contractile response of the guinea pig bronchus partly through NK(2) receptor stimulation.     

Tachykinin NK1 and NK2 receptor antagonists and atropine-resistant ascending excitatory reflex to the circular muscle of the guinea-pig ileum.

1. The aim of this study was to investigate the effect of various antagonists, selective for the tachykinin NK1 or NK2 receptor, on the atropine-resistant ascending excitatory reflex (AER) to the circular muscle of the guinea-pig ileum elicited by radial stretch (balloon distension) or electrical field stimulation. 2. Submaximal and maximal atropine- (1 microM) resistant AER elicited by balloon distension averaged about 40-50% and 70-90% of maximal circular spasm to 80 mM KCl, respectively. The NK1 receptor antagonist, (+/)-CP 96,345 (1 microM) inhibited both maximal and submaximal AER. FK 888 (1-3 microM) inhibited submaximal AER only. RP 67,580 (1 microM) was ineffective. The NK2 receptor antagonist, GR 94,800, inhibited both maximal and submaximal AER at all concentrations tested (0.1-3.0 microM), while SR 48,968 was effective only at 1.0 microM. The NK2 receptor antagonists, MEN 10,376 and MEN 10,573 inhibited both submaximal and maximal AER at 10 and 1.0 microM, respectively. 3. In other experiments, an NK1 receptor antagonist, (+/-)-CP 96,345 or FK 888 (1.0 microM in each case) was administered first and the effect of GR 94,800 (1.0 microM) on the residual AER response was determined; or GR 94,800 was administered first and the effect of (+/-)-CP 96,345 or FK 888 was determined. The results of these experiments indicated an additive effect produced by the combined treatment with NK1 and NK2 receptor antagonists.(ABSTRACT TRUNCATED AT 250 WORDS)     

Tachykinin NK1 receptor antagonists for the control of chemotherapy-induced nausea and vomiting

The treatment of neoplastic disease with chemotherapeutic cytotoxic drugs has long been associated with profound nausea and vomiting (emesis). This became the most feared side effect of this type of treatment and was so severe that some patients would withdraw from further treatment, thus jeopardising their clinical outcome and possibly life expectancy. The introduction of the 5-HT₃ receptor antagonists had a significant impact in this area, offering substantial reductions in emesis, largely through prophylactic treatment. Unfortunately, some forms of emesis were resistant to treatment with these drugs, so the search has continued to identify new chemical entities with a higher level of efficacy and a broader spectrum of activity. Data generated in animals has identified tachykinin NK₁ receptors as highly important in the emetic reflex and experimental evidence strongly supports NK₁ receptor antagonists as highly efficacious anti-emetic agents, with unparalleled broad spectrum activity. Several novel antagonists have recently entered clinical development and data are emerging to support their anti-emetic activity. This area continues to attract substantial medicinal chemical research effort. Most major pharmaceutical companies are seeking new matter through structural refinement of early leads or discovery of novel compounds from library screening. The scope of chemical lead matter has advanced from early piperidine and quinuclidines to a spectrum of templates that improve expectations for a well-tolerated therapeutic agent. Recent success in combining 5-HT₃ and NK₁ antagonists in emesis treatment is expected to greatly advance clinical outcomes with newer and safer agents.     

Tachykinin NK(2) receptors and enhancement of cholinergic transmission in the inflamed rat colon: an in vivo motility study

In the gastrointestinal tract, tachykinin NK(2) receptors are localized both on smooth muscle and nerve fibres. NK(2) receptor antagonists reduce exaggerated intestinal motility in various diarrhoea models but the site of action contributing to this effect is unknown. In this study we investigated the effects of atropine (1.4 micromol kg(-1), i.v.), hexamethonium (13.5 micromol kg(-1), i.v.), and nepadutant (0.1 micromol kg(-1), i.v.), a selective tachykinin NK(2) receptor antagonist, on distension (0.5 and 1 ml)-, or irritation (acetic acid, 0.5 ml of 7.5% v v(-1))-induced motility in the rat distal colon in vivo. The effects of atropine, hexamethonium or N(omega)-nitro-L-argininemethylester (L-NAME, 1.85 micromol kg(-1), i.v.) on [betaAla(8)]NKA(4-10) (10 nmol kg(-1), i.v.)-induced colonic contractions were also investigated. When the colonic balloon was filled with a subthreshold volume (0.5 ml), the intraluminal instillation of acetic acid triggered a high-amplitude phasic colonic motility which was partially reduced by nepadutant and suppressed by either hexamethonium or atropine. Filling of the balloon with 1 ml evoked reflex (hexamethonium-sensitive), atropine-sensitive phasic colonic motility: nepadutant had no significant effect on the distension-evoked motility. Neither hexamethonium nor atropine significantly reduced [betaAla(8)]NKA(4-10)-induced colonic contractions, whereas nepadutant suppressed them. Following L-NAME pretreatment, [betaAla(8)]NKA(4-10)-induced colonic contractions were inhibited by both atropine and hexamethonium. In hexamethonium-pretreated animals, an atropine-sensitive component of [betaAla(8)]NKA(4-10)-induced colonic contractions was also evident. These results indicate that the application of irritants onto the colonic mucosa induces the release of endogenous tachykinins which enhance excitatory cholinergic mechanisms through the stimulation of NK(2) receptors.     

Inhibition of guinea-pig and human sensory nerve activity and the cough reflex in guinea-pigs by cannabinoid (CB2) receptor activation

1. There is considerable interest in novel therapies for cough, since currently used agents such as codeine have limited beneficial value due to the associated side effects. Sensory nerves in the airways mediate the cough reflex via activation of C-fibres and RARs. Evidence suggests that cannabinoids may inhibit sensory nerve-mediated responses. 2. We have investigated the inhibitory actions of cannabinoids on sensory nerve depolarisation mediated by capsaicin, hypertonic saline and PGE2 on isolated guinea-pig and human vagus nerve preparations, and the cough reflex in conscious guinea-pigs. 3. The non-selective cannabinoid (CB) receptor agonist, CP 55940, and the selective CB2 agonist, JWH 133 inhibited sensory nerve depolarisations of the guinea-pig vagus nerve induced by hypertonic saline, capsaicin and PGE2. These responses were abolished by the CB2 receptor antagonist SR144528, and unaffected by the CB1 antagonist SR141716A. Similarly, JWH 133 inhibited capsaicin-evoked nerve depolarisations in the human vagus nerve, and was prevented by SR144528. 4. Using a guinea-pig in vivo model of cough, JWH 133 (10 mg kg-1, i.p., 20 min) significantly reduced citric acid-induced cough in conscious guinea pigs compared to those treated with the vehicle control. 5. These data show that activation of the CB2 receptor subtype inhibits sensory nerve activation of guinea-pig and human vagus nerve, and the cough reflex in guinea-pigs, suggesting that the development of CB2 agonists, devoid of CB1-mediated central effects, will provide a new and safe antitussive treatment for chronic cough.     

Tachykinin NK1 and NK3 receptors in the prefrontal cortex of the human brain

1. The tachykinins are neuropeptides found in both the central and peripheral nervous systems that play a role in inflammation and pain mechanisms and some autonomic reflexes and behaviours. 2. Although the distribution of the tachykinin receptors has been described in the brains of various animal species, little is known about the distribution of the NK1 and NK3 receptors in the human brain. 3. The present paper examines the distribution of the NK1 and NK3 receptors in the prefrontal cortex of formalin-fixed postmortem human brain tissue by immunohistochemical techniques. 4. The majority of NK1 receptor immunoreactivity appeared as a thin band of punctate staining at the pial surface, with dark brown dots of NK1 receptor immunoreactivity predominantly scattered across the mid to upper cortical layers. 5. The NK3 receptor immunoreactivity was found in the glia limitans at the pial surface, where astrocytes and beaded fibres were intensely stained. Dots of NK3 receptor immunoreactivity were scattered across all cortical layers. In the white matter, astrocytes and beaded fibres displayed NK3 receptor immunoreactivity, particularly in areas surrounding blood vessels.     

Tachykinin NK1 receptor in the guinea-pig isolated proximal urethra: characterization by receptor selective agonists and antagonists.

1. The tachykinin receptor mediating contraction of the guinea-pig isolated proximal urethra has been characterized by use of receptor selective agonists and antagonists. All experiments were performed in the presence of peptidase inhibitors (bestatin, captopril and thiorphan, 1 microM each) in order to reduce peptide degradation. 2. The natural tachykinins, substance P and neurokinin A produced a concentration-dependent contraction of rings of the proximal urethra which approached the same maximum (about 50% of the response to 80 mM KCl). Substance P (EC50 155 nM) was slightly (3.6 times) more potent than neurokinin A (EC50 560 nM). 3. The tachykinin NK1 receptor selective agonist, [Sar9]substance P sulphone (EC50 62 nM), was slightly more potent than substance P and produced the same maximal response of natural tachykinins. The NK2 receptor selective agonist, [beta Ala8] neurokinin A(4-10), was active only at microM concentrations and its maximal effect did not exceed 20% of that to substance P or neurokinin A. The NK3 receptor selective agonist, senktide, was ineffective up to 30 microM. 4. The response to [Sar9]substance P sulphone was antagonized in a competitive manner by either (+/-)-CP 96,345 (pA2 7.75, slope - 1.10) or GR 82,334 (pA2 7.31, slope - 1.26), which are selective NK1 receptor antagonists, while it was unaffected (up to 10 microM) by MEN 10,376, a selective NK2 receptor antagonist. 5. The response to 10 microM [beta Ala8]neurokinin A (4-10) was abolished by either 0.2 microM (+/-)-CP 96,345 or 1 microM GR 82,334, suggesting the involvement of NK1 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intra-amygdala injection of the substance P [NK(1) receptor] antagonist L-760735 inhibits neonatal vocalisations in guinea-pigs.

The involvement of the basolateral amygdala in mediating the inhibition of neonatal vocalisation by substance P (NK(1) receptor) antagonists was examined. These studies determined whether the time course for separation-induced vocalisations in guinea-pig pups coincided with NK(1) receptor internalisation (a marker of substance P release) in the amygdala, and whether vocalisations could be blocked by focal injection of the NK(1) receptor antagonist L-760735 into this brain region. The peak period for neonatal vocalisations occurred 5-10 min following maternal separation. This coincided with the peak increase in the number of cells in the basolateral amygdala exhibiting NK(1) receptor endocytosis, consistent with the proposal that substance P is released in the amygdala as a result of isolation stress. Focal injection of L-760735 (15 nmol per side) but not L-770765 (an analogue of L-760735 which has low NK(1) receptor affinity) into the basolateral amygdala attenuated separation-induced vocalisations. In contrast, injection of L-760735 (15 nmol per side) into the dorsal ventricular nucleus of the thalamus, a region with relatively low density of NK(1) receptors, had no effect on neonatal vocalisations. These findings are consistent with other evidence that the amygdala is one possible site of action for the inhibition of neonatal vocalisations by substance P antagonists.     

Effect of the long-acting tachykinin NK(1) receptor antagonist MEN 11467 on tracheal mucus secretion in allergic ferrets

1. We investigated the effect of MEN 11467 ((1R,2S)-2-N[1(H)indol-3-yl-carbonyl]-1-N-[N(alpha)(p-tolylacetyl)-N(alpha)(methyl)-D-3-(2-naphthyl)alanyl]diaminocyclohexane) on tachykinin-induced mucus secretion in ferret trachea in vitro and determined its effect on secretion by tracheae from allergic ferrets in response to allergen challenge. 2. Repeated administration of [Sar(9),Met(O(2))(11)]-substance P ([Sar(9)]SP, 1 microM) maintained mucus output above control values for at least 1.75 h. MEN 11467 inhibited secretion in a concentration-dependent manner with maximal inhibition at 10 microM and an approximate IC(50) of 0.3 microM. Inhibition by MEN 11467 (0.1--10 microM) was maintained, to varying degree, for at least 1.75 h after washout in the continued presence of [Sar(9)]SP. 3. In electrically stimulated tracheae, tachykininergic neural secretion was virtually abolished by 1 microM MEN 11467. 4. In tracheae from ovalbumin-sensitised animals, repeated administration of ovalbumin maintained mucus output above controls for 1.5 h. MEN 11467 inhibited ovalbumin-induced secretion in a concentration-dependent manner, with complete inhibition at 1 microM. Inhibition by MEN 11467 (1 and 10 microM) was maintained, to varying degree, after drug washout for the 1.5 h of ovalbumin stimulation. 5. MEN 11467 1 microM did not affect secretion induced by either acetylcholine or histamine, whereas 10 microM MEN 11467 did inhibit agonist-induced secretion. 6. We conclude that, in ferret trachea in vitro, MEN 11467 at concentrations of 0.1--1 microM is a long acting and selective inhibitor of tachykininergic-induced mucus secretion, and may have therapeutic potential for bronchial hypersecretion associated with allergic conditions, for example in asthma.     

The first de novo-designed antagonists of the human NK(2) receptor

The de novo molecular design program SPROUT has been used in conjunction with a molecular model to produce a molecular template for a new class of NK(2) receptor antagonist. An efficient, stereocontrolled synthesis of a small series of molecules, designed to test the validity of this template, was developed. Competition assays using recombinant human NK(2) receptor support the structural requirements of this new designed molecular template.