Neurogenic plasma leakage in mouse airways

1. This study sought to determine whether neurogenic inflammation occurs in the airways by examining the effects of capsaicin or substance P on microvascular plasma leakage in the trachea and lungs of male pathogen-free C57BL/6 mice. 2. Single bolus intravenous injections of capsaicin (0.5 and 1 micromol kg(-1), i.v.) or substance P (1, 10 and 37 nmol kg(-10, i.v.) failed to induce significant leakage in the trachea, assessed as extravasation of Evans blue dye, but did induce leakage in the urinary bladder and skin. 3. Pretreatment with captopril (2.5 mg kg(-1), i.v.), a selective inhibitor of angiotensin converting enzyme (ACE), either alone or in combination with phosphoramidon (2.5 mg kg(-1), i.v.), a selective inhibitor of neutral endopeptidase (NEP), increased baseline leakage of Evans blue in the absence of any exogenous inflammatory mediator. The increase was reversed by the bradykinin B2 receptor antagonist Hoe 140 (0.1 mg kg(-1), i.v.). 4. After pretreatment with phosphoramidon and captopril, capsaicin increased the Evans blue leakage above the baseline in the trachea, but not in the lung. This increase was reversed by the tachykinin (NK1) receptor antagonist SR 140333 (0.7 mg kg(-1), i.v.), but not by the NK2 receptor antagonist SR 48968 (1 mg kg(-1), i.v.). 5. Experiments using Monastral blue pigment as a tracer localized the leakage to postcapillary venules in the trachea and intrapulmonary bronchi, although the labelled vessels were less numerous in mice than in comparably treated rats. Blood vessels of the pulmonary circulation were not labelled. 6. We conclude that neurogenic inflammation can occur in airways of pathogen-free mice, but only after the inhibition of enzymes that normally degrade inflammatory peptides. Neurogenic inflammation does not involve the pulmonary microvasculature.     

Evidence of a role for NK1 and CGRP receptors in mediating neurogenic vasodilatation in the mouse ear

The aims of this study were to develop a technique to measure blood flow in the mouse ear and to investigate the nature of the vasodilator mediator(s) involved in the response to capsaicin. The response to capsaicin, applied topically, was investigated in anaesthetized CD1 or Sv129+C57BL/6 wild-type (+/+) or NK(1) receptor knockout mice (-/-). Blood flow was assessed by laser Doppler flowmetry and oedema formation by (125)I-albumin accumulation. Capsaicin induced significant increases in blood flow (0.2 - 200 microg in 20 microl) and oedema (2 - 200 microg in 20 microl). The oedema response was absent in NK(1)-/- mice and NK(1)+/+mice treated with the selective NK(1) receptor antagonist SR140333 (480 nmol kg(-1)) as expected. Furthermore, the capsaicin-evoked increase in blood flow was significantly potentiated in the knockout mice (203% of wild-type response, P<0.05) and wild-type mice treated with SR140333 (201%, P<0.05). The CGRP receptor antagonist CGRP(8 - 37) (400 nmol kg(-1)) had no effect on capsaicin-induced blood flow in NK(1)+/+mice but abolished the increased blood flow to capsaicin in NK(1)-/-, and NK(1)+/+wild-type mice pre-treated with SR140333. The results indicate that neurogenic vasodilatation can be measured in the mouse ear. The capsaicin-induced increased blood flow involves activation of, and possible interactions between, both NK(1) and CGRP(1) receptors.     

Involvement of sensory neuropeptides in the development of plasma extravasation in rat dorsal skin following thermal injury.

1. The involvement of the neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP) in plasma extravasation following thermal injury of rat dorsal skin was investigated. 2. Heat applied to the dorsal skin of anaesthetized rats by a temperature-controlled skin heater (1 cm diameter) for 5 min induced temperature-dependent plasma protein extravasation at 46 degrees C to 50 degrees C measured over the 20 min following initiation of heat. 3. The NK1-receptor antagonist, SR140333, at doses above 36 nmol kg-1, significantly (P < 0.05) inhibited plasma extravasation by up to 79 +/- 3% (120 nmol kg-1) after heat application at 48 degrees C and by up to 53 +/- 10% (120 nmol kg-1) after heat application at 50 degrees C. 4. The CGRP1-receptor antagonist, CGRP8-37, at doses of 200 and 400 nmol kg-1, significantly inhibited (P < 0.01) plasma extravasation by 55 +/- 9 and 60 +/- 12%, respectively, after heat application at 48 degrees C. At a dose of 200 nmol kg-1 CGRP8-37 inhibited plasma extravasation by 41 +/- 8% after heat application at 50 degrees C. 5. SR140333, 120 nmol kg-1, and CGRP8-37, 200 nmol kg-1 together significantly (P < 0.01) inhibited plasma extravasation by 84 +/- 15% after heating at 48 degrees C for 5 min. 6. In experiments where the response was measured for 0-5, 5-10, 10-15 or 15-20 min, SR140333, 120 nmol kg-1, significantly (P < 0.05) inhibited plasma extravasation which had accumulated during all the time periods measured. In comparison, CGRP8-37, 200 nmol kg-1, was significantly (P < 0.05) effective at time-points up to 15 min after initiation of injury. 7. In longer term experiments plasma protein extravasation continued for at least 95 min after initiation of thermal injury. SR140333, at a dose of 120 nmol kg-1, significantly inhibited plasma extravasation for up to 65 min after initiation of injury. 8. In conclusion, the data from the present study demonstrate that both SP and CGRP are likely to have a role in the acute plasma extravasation after thermal injury. In addition, evidence suggests SP may have a role in plasma extravasation for up to 65 min.     

Effects of STA(2), a thromboxane A(2) mimetic, in inducing airflow obstruction and airway microvascular leakage in guinea pigs

BACKGROUND: U-46619, a thromboxane A(2) (TXA(2)) mimetic, is shown to cause airway microvascular leakage, although the effects is weak when comparing with that to induce bronchoconstriction in guinea pigs. OBJECTIVE: In order to know the airway effect of TXA(2) more accurately, we have examined the effects of STA(2), a TXA(2) mimetic with higher affinity to TXA(2) (TP) receptors than U-46619, to induce airway microvascular leakage and airflow obstruction. METHODS: Anesthetized and ventilated guinea pigs were i.v. given STA(2) (3-30 nmol/kg) or U-46619 (3-100 nmol/kg) 1 min after i.v. Evans blue dye. STA(2)- and U-46619-induced increases in lung resistance (R(L)) was measured for 6 min. The amount of extravasated Evans blue dye in the lower airways was, then, examined as an index of leakage. In selected animals, specific TP receptor antagonists (10 microg/kg S-1452 or 10 mg/kg ONO-3708) were pretreated i.v. RESULTS: Both STA(2) and U-46619 induced significant increases in leakage and airflow obstruction. However, STA(2) induced a slow and significantly less increase in R(L) but caused a significantly greater increase in extravasation of Evans blue dye compared to U-46619. Specific TP receptor antagonists completely abolished both airway effects induced by STA(2) and U-46619. CONCLUSION: Our present results have supported a possibility that TXA(2) induces microvascular leakage as well as bronchoconstriction in the airways.     

Reduced inflammation in genetically hypertensive rat airways is associated with reduced tachykinin NK(1) receptor numbers

The airways of the genetically hypertensive rat (GH) are hyperinnervated by substance P-containing sensory nerves and exhibit reduced inflammatory responsiveness to substance P and to capsaicin. The present study measured tracheal inflammation to resiniferatoxin (1.0 microgram/kg i.v.), a capsaicin analogue, which lacks the hypotensive action of capsaicin itself, alone or after the neuronal nitric oxide synthase inhibitor 1-(2-trifluoromethylphenyl)imidazole (TRIM) (50 mg/kg i.p.). The inflammatory response to resiniferatoxin alone was 50% lower in untreated GH than in control rats, a similar strain difference to that seen previously with capsaicin. Pre-treatment with TRIM had no effect on inflammation in either strain. Binding kinetics of the tachykinin NK(1) receptor antagonist [3H](S)-1-(2-[3-(3, 4-dichlorophenyl)-1-(3-isopropoxyphenylacetyl)piperidin-3-yl]ethyl)-4- phenyl-l-azoniabicyclo[2,2,2,]octane chloride ([3H]SR140333)(0.125-16.0 nM) showed 50% reduction of B(max) in GH versus control tracheae (74+/-13 cf.165+/-26 fmol/mg protein). Our results indicate that the reduced neurogenic inflammatory responsiveness in GH rats can be attributed entirely to reduced tachykinin NK(1) receptor numbers.     

Leukotriene D4- and prostaglandin F2 alpha-induced airflow obstruction and airway plasma exudation in guinea-pig: role of thromboxane and its receptor.

1. We studied the effects of a thromboxane A2 receptor (TP receptor) antagonist, ICI-192,605 (0.5 mg kg-1, i.v.) and a selective thromboxane (Tx) synthetase inhibitor, OKY-046 (30 mg kg-1, i.v.), on airway responses induced by leukotriene D4 (LTD4; 0.2 nmol) or prostaglandin F2 alpha (PGF2 alpha; 20 nmol) instilled via the airways route to anaesthetized guinea-pigs. For a comparison, airway responses to a TxA2-mimetic, U-46619 (0.02 nmol) were also studied. We measured both lung resistance (RL) to monitor airflow obstruction, and extravasation of Evans Blue dye to quantify airway plasma exudation. 2. Instilled LTD4 into the tracheal lumen induced an immediate peak and subsequently persistent increase in RL and produced a large amount of extravasation of Evans Blue dye at all airway levels. Both ICI-192,605 and OKY-046 significantly attenuated the persistent increase in RL following the immediate response and reduced LTD4-induced extravasation of Evans Blue dye in the trachea and proximal intrapulmonary airway. Instilled LTD4 produced significant increases in immunoreactive TxB2 in bronchoalveolar lavage fluid obtained 1.5 min after instillation of LTD4. 3. Instilled PGF2 alpha into the tracheal lumen induced an immediate increase in RL which peaked at approximately 15 s. We also observed a delayed sustained increase in RL, reaching a second peak at approximately 4 min. PGF2 alpha produced small but significant increases in the amount of Evans Blue dye at all airway levels. As with PGF2 alpha, instillation of U-46619 produced a biphasic increase in RL and extravasation of Evans Blue dye.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects and interactions of sensory neuropeptides on airway microvascular leakage in guinea-pigs.

1. We have studied the effect of the sensory neuropeptides substance P (SP), neurokinin A (NKA), neurokinin B (NKB) and calcitonin gene-related peptide (CGRP) on microvascular permeability in guinea-pig airways in vivo and investigated whether CGRP would potentiate the effect of SP. We used the extravasation of intravenously-injected Evans blue dye as an index of permeability. 2. The tachykinins SP, NKA and NKB (0.025-5.0 nmol kg-1, i.v.) significantly (P less than 0.05) increased extravasation of dye in a dose-related manner and with a similar pattern of distribution; they were most potent in the trachea and main bronchi, less potent in the larynx and intrapulmonary airways, and had little significant effect in the bladder. 3. SP was significantly more potent in causing extravasation of dye than NKA or NKB with ED50 values (nmol kg-1) in the range 0.04-0.1, depending on the airway level, compared with values in the range 0.3-0.7 for the neurokinins. 4. CGRP (0.0025-2.5 nmol kg-1, i.v.) had no significant effect on microvascular permeability and did not potentiate SP-induced extravasation of dye. 5. Each neuropeptide decreased mean arterial blood pressure, indicating vasodilatation, in a dose-related manner. Co-injection of CGRP and SP produced additive decreases in arterial pressure. 6. We conclude that, in guinea-pig airways, tachykinins increase microvascular permeability via tachykinin receptors of the NK-1 sub-type (indicated by an order of potency of SP greater than NKA = NKB) on endothelial cells. The response appears to be related to mechanisms in addition to vasodilatation. The relevance of the responses to the tachykinins in asthma is discussed.     

BradykMn-induced airway microvasciilar leakage is potentiated by captopril and phosphoramidon

Bradykinin can be inactivated by the peptidases angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP), both of which are present in the airways. We evaluated the role of these enzymes in bradykinin-induced airway microvascular leakage and lung resistance in anesthetized and mechanically ventilated guinea pigs. We studied the effects of captopril (inhaled; 350 nmol), a specific ACE inhibitor, and phosphoramidon (inhaled; 7.5 nmol), a specific NEP inhibitor. Airway microvascular leakage was measured with the albumin marker Evans Blue dye (20 mg/kg i.v.), and airflow obstruction was measured as lung resistance (R_L). Bradykinin was given by inhalation (0.1, 0.3 and 1 mM; 45 breaths), and caused a dose-dependent increase in both R_L and airway microvascular leakage. Inhibition of NEP or ACE potentiated the bradykinin-induced microvascular leakage in main bronchi and proximal and distal intrapulmonary airways. However, only NEP inhibition significantly potentiated the extravasation of Evans Blue dye into the tracheal wall and lumen. The combined inhibition of NEP and ACE significantly potentiated plasma leakage at all airway levels, as well as the increase in R_L induced by inhaled bradykinin. Recovery R_L after one lung inflation significantly correlated with the extravasation of Evans Blue dye in the tissue at all airway levels, indicating that airway edema may have contributed to airway narrowing. We conclude that in the guinea pig, both NEP and ACE modulate bradykinin-induced airway microvascular leakage.     

Attenuation of tachykinin-induced airflow obstruction and microvascular leakage in immature airways.

1. To study the effect of maturation on substance P (SP)- and neurokinin A (NKA)-induced airflow obstruction and airway microvascular leakage (MVL), we have measured changes in both lung resistance (RL) and extravasation of Evans blue dye in anaesthetized immature (aged 14 +/- 1 days) and adult guinea-pigs (aged 80 +/- 3 days). 2. RL and its recovery after hyperinflation at 5 min were measured for 6 min after i.v. SP (0.2, 1 and 30 nmol kg-1), NKA (1 and 10 nmol kg-1) or vehicle (0.9% NaCl). After measurement of RL, MVL in trachea, main bronchi and intrapulmonary airways was also examined. 3. The order of potency in inducing airflow obstruction did not change with age (NKA > SP) but immature animals required a larger dose of SP or NKA than adults to cause a significant increase in RL. 4. The order of potency in inducing airway microvascular leakage was SP > NKA in both immature and adult animals. The amount of extravasated dye after SP was significantly less in immature airways, especially in central airways. 5. Phosphoramidon (2.5 mg kg-1), a neutral endopeptidase (NEP) inhibitor, significantly increased RL after 0.2 nmol kg-1 SP only in adult airways. Phosphoramidon enhanced the dye extravasation after 0.2 nmol kg-1 SP in both immature and adult airways with a significantly greater amount of dye in adult animals, suggesting that mechanisms other than changes in NEP activity may be responsible for this age-related difference.(ABSTRACT TRUNCATED AT 250 WORDS)     

Involvement of tachykinins in plasma extravasation induced by bradykinin and low pH medium in the guinea-pig conjunctiva.

1. The effect of bradykinin, capsaicin, substance P and low pH medium on plasma extravasation in the guinea-pig conjunctiva has been studied. Evans blue dye was measured in the conjunctiva after local instillation of the agents into the conjunctival sac. 2. Bradykinin (2-50 nmol), capsaicin (20-50 nmol) and substance P (0.5-5 nmol) caused a dose-dependent increase in plasma extravasation with the following order of potency: substance P > bradykinin = capsaicin. The effect of capsaicin (50 nmol) and substance P (5 nmol) was abolished by the tachykinin NK1 receptor antagonist, CP-99,994 (8 mumol kg-1, i.v.) (P < 0.01), whereas CP-100,263 (8 mumol kg-1, i.v.) the inactive enantiomer of CP-99,994 was without effect. CP-99,994 inhibited by 70% (P < 0.01) the effect of bradykinin. 3. The kinin B2 receptor antagonist, Hoe 140 (icatibant, 10 nmol kg-1, i.v.) abolished the response to bradykinin (50 nmol) (P < 0.01), but did not affect the responses to capsaicin (50 nmol) or substance P (5 nmol). Plasma extravasation induced by low pH medium (pH 1) was abolished by CP-99,994 (P < 0.01) and by Hoe 140 (P < 0.01). 4. The present findings suggest that: endogenous or exogenous tachykinins increase plasma extravasation in the guinea-pig conjunctiva by activation of NK1 receptors; bradykinin-induced plasma extravasation is mediated by tachykinin release from sensory nerve endings; low pH media cause plasma extravasation via release of kinins that by activation of B2 receptors release tachykinins from sensory nerve endings.     

The non-peptide NK1 receptor antagonist SR140333 produces long-lasting inhibition of neurogenic inflammation,but does not influence acute chemo- or thermonociception in rats

In anaesthetized rats, the neurokinin (NK)₁ receptor antagonist SR140333 (10–1000 g/kg) stereoselectively inhibited mustard oil-induced plasma protein extravasation in the dorsal skin of the hind paw. After s.c. administration of SR140333, inhibition of plasma protein extravasation was maximal 3 h after injection. A dose of 0.1 mg/kg i.v. or 1.0 mg/kg s.c. produced long-lasting inhibition which was still significant 24 h after treatment.Since systemic administration of SR140333 has been shown to inhibit nociceptive responses in anaesthetized rats, we wanted to evaluate a possible effect of SR140333 on chemo- and thermonociception in conscious rats. SR140333 (100 g/kg s.c) did not reduce the behavioral response of rats to the irritant effect of capsaicin in the wiping test, nor did it affect the thermal nociceptive threshold in the plantar test. Furthermore, the decrease in thermal nociceptive threshold which was produced by intraplanter injection of PGE₂, and which has been shown to be entirely dependent on capsaicin-sensitive afferents, was not affected by treatment with this NK₁ receptor antagonist.These results show that systemic administration of SR140333, at doses which cause inhibition of neurogenic inflammation, has no detectable effect on acute chemo- or thermonociception in conscious rats.     

Inflammatory oedema induced by phospholipases A2 isolated from Crotalus durissus sp. in the rat dorsal skin: a role for mast cells and sensory C-fibers.

The ability of the phospholipases A(2) (PLA(2)s) from Crotalus durissus cascavella, Crotalus durissus collilineatus and Crotalus durissus terrificus venoms and crotapotin to increase the vascular permeability in the rat skin as well as the contribution of both mast cells and sensory C-fibers have been investigated in this study. Vascular permeability was measured as the plasma extravascular accumulation at skin sites of intravenously injected 125I-human serum albumin. Intradermal injection of crotalic PLA(2)s (0.05-0.5 microg/site) in the rat skin resulted in dose-dependent increase in plasma extravascular whereas crotapotin (1 microg/site) failed to affect this response. Co-injection of crotapotin (1 microg/site) did not modify the increased vascular permeability induced by the PLA(2)s (0.05-0.5 microg/site). Previous treatment (30 min) of the animals with cyproheptadine (2 mg/kg, i.p.) markedly reduced PLA(2) (0.5 microg/site)-induced oedema. In rats treated neonatally with capsaicin to deplete neuropeptides, the plasma extravasation induced by all PLA(2)s (0.5 microg/site) was also significantly reduced. Similarly, the tachykinin NK(1) receptor antagonist SR140333 (1nmol/site) significantly reduced the PLA(2)-induced oedema. In addition, the combination of SR140333 with cyproheptadine further reduced the increased plasma extravasation by PLA(2) from C. d. cascavella venom, but not by PLA(2) from C. d. terrificus and C. d. collilineatus venoms. Our results suggest that increase in skin vascular permeability by crotalic PLA(2)s is mediated by activation of sensory C-fibers culminating in the release of substance P, as well as by activation of mast cells which in turn release amines such as histamine and serotonin.     

Hydrogen sulfide causes vanilloid receptor 1-mediated neurogenic inflammation in the airways

Hydrogen sulfide (H(2)S) is described as a mediator of diverse biological effects, and is known to produce irritation and injury in the lung following inhalation. Recently, H(2)S has been found to cause contraction in the rat urinary bladder via a neurogenic mechanism. Here, we studied whether sodium hydrogen sulfide (NaHS), used as donor of H(2)S, produces responses mediated by sensory nerve activation in the guinea-pig airways. NaHS evoked an increase in neuropeptide release in the airways that was significantly attenuated by capsaicin desensitization and by the transient receptor potential vanilloid 1 (TRPV1) antagonist capsazepine. In addition, NaHS caused an atropine-resistant contraction of isolated airways, which was completely prevented by capsaicin desensitization. Furthermore, NaHS-induced contraction was reduced by TRPV1 antagonism (ruthenium red, capsazepine and SB366791), and was abolished by pretreatment with the combination of tachykinin NK(1) (SR140333) and NK(2) (SR48968) receptor antagonists. In anesthetized guinea-pigs, intratracheal instillation of NaHS increased the total lung resistance and airway plasma protein extravasation. These two effects were reduced by TRPV1 antagonism (capsazepine) and tachykinin receptors (SR140333 and SR48968) blockade. Our results provide the first pharmacological evidence that H(2)S provokes tachykinin-mediated neurogenic inflammatory responses in guinea-pig airways, and that this effect is mediated by stimulation of TRPV1 receptors on sensory nerves endings. This novel mechanism may contribute to the irritative action of H(2)S in the respiratory system.     

The plasma protein extravasation induced by adenosine and its analogues in the rat dorsal skin: evidence for the involvement of capsaicin sensitive primary afferent neurones and mast cells

1. The contribution of sensory neurons and mast cells to the oedema evoked by adenosine A1 (N(6)-cyclopentyladenosine, CPA, 3 - 30 nmol site(-1)), A2 (5'N-ethylcarboxamidoadenosine, NECA, 1 - 10 nmol site(-1)) and A3 receptor agonists (N6-[3-iodobenzyl]-N-methyl-5'-carboxiamidoadenosine, IB-MECA, 0.01 - 3 nmol site(-1)) was investigated in the rat skin microvasculature, by the extravascular accumulation of intravenously-injected (i.v.) 125I-albumin. 2. Intradermal (i.d.) injection of adenosine and analogues induced increased microvascular permeability in a dose-dependent manner (IB-MECA > NECA > CPA > adenosine). The non-selective adenosine receptor antagonist theophylline (5 - 50 nmol site(-1)) markedly inhibited adenosine, CPA or NECA but not IB-MECA-induced plasma extravasation. The A1 receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX, 0.3 - 3 micromol kg(-1), i.v.) significantly reduced CPA-induced plasma extravasation whereas responses to adenosine, NECA or IB-MECA were unchanged. The A2 receptor antagonist 3,7-dymethyl-1-proprargylxanthine (DMPX, 0.5 - 50 nmol site(-1)) significantly reduced NECA-induced plasma extravasation without affecting responses to adenosine, CPA and IB-MECA. 3. The tachykinin NK1 receptor antagonist (S)-1-[2-[3-(3,4-dichlorphenyl)-1 (3-isopropoxyphenylacetyl) piperidin-3-yl] ethyl]-4-phenyl-1 azaniabicyclo [2.2.2]octane chloride (SR140333), but not the NK2 receptor antagonist (S)-N-methyl-N[4-acetylamino-4-phenyl piperidino)-2-(3,4-dichlorophenyl)butyl]-benzamide (SR48968), significantly inhibited the plasma extravasation evoked by higher doses of adenosine (100 nmol site(-1)), CPA (100 nmol site(-1)), NECA (1 nmol site(-1)) and IB-MECA (0.1 - 1 nmol site(-1)). In rats treated with capsaicin to destroy sensory neurons, the response to higher doses of adenosine, CPA and NECA, but not IB-MECA, was significantly inhibited. 4. The effects of adenosine and analogues were largely inhibited by histamine and 5-hydroxytryptamine (5-HT) antagonists and by compound 48/80 pretreatment. 5. In conclusion, our results provide evidence that adenosine A1 and A2, but not A3, receptor agonists may function as cutaneous neurogenic pro-inflammatory mediators; acting via microvascular permeability-increasing mechanisms that can, depending on dose of agonist and purine receptor under study, involve the tachykinin NK1 receptor and mast cell amines.     

Nociceptin inhibits airway microvascular leakage induced by HCl intra-oesophageal instillation

1. Gastro-oesophageal acid reflux may cause airway responses such as cough, bronchoconstriction and inflammation in asthmatic patients. Our previous results suggest that microvascular leakage induced, in the guinea-pig airways, by intra-oesophageal hydrochloric acid (HCl) infusion was mainly dependent on the release of tachykinins. Nociceptin, an endogenous ligand of the opioid receptor NOP, has been shown to inhibit bronchoconstriction and cough in guinea-pig or cat by inhibiting tachykinin release. 2. The purpose of this study was to investigate the effects of nociceptin on the intra-oesophageal HCl-induced airway microvascular leakage evaluated by Evans blue dye extravasation measurement in anaesthetised guinea-pigs pretreated with propranolol, atropine and phosphoramidon. 3. Infusion of intra-oesophageal HCl led to a significant increase in plasma extravasation in the main bronchi and trachea. This increase was abolished when animals underwent a bilateral vagotomy. 4. Airway microvascular leakage was inhibited by nociceptin (3-30 microg x kg(-1) i.v.) in a dose-dependent manner (maximal inhibition at the dose of 30 microg x kg(-1): 19.76+/-1.13 vs 90.92+/-14.00 ng x mg(-1) tissue for nociceptin and HCl infusion, respectively, in the main bronchi, P<0.01). The NOP receptor agonist [Arg(14),Lys(15)]N/OFQ mimicked the inhibitory effect of nociceptin, but at a 10-fold lower dose (3 microg x kg(-1) i.v). The NOP receptor antagonist J-113397 had no effect on plasma protein extravasation by itself, but was able to block the inhibitory effect of nociceptin. 5. Morphine (1 mg x kg(-1)) had a similar inhibitory effect as that of nociceptin. Naloxone pretreatment abolished the effect of morphine, but was enable to block the inhibitory effect of nociceptin. 6. Under similar conditions, nociceptin, in the previous range of concentration, was unable to counteract the airway microvascular leakage induced by substance P (SP). 7. These results suggest that airway plasma extravasation induced by intra-oesophageal HCl instillation might be inhibited by specific stimulation of the NOP receptor with nociceptin. Nociceptin is likely to act at a pre-junctional level, by inhibiting tachykinin release, since it was unable to prevent SP-induced airway plasma extravasation.     

Substance P in sensory nerve fibres contributes to the development of oedema in the rat hind paw after thermal injury.

Immersion of the hind paws of anesthetized rats in hot water for 5 min induced massive plasma protein leakage as indicated by extravasation of Evans blue dye in the skin. The threshold temperature which caused noticeable plasma extravasation was 45 degrees C, a maximal response was obtained between 55 degrees C and 60 degrees C. Pretreatment of rats 2 days after birth with 50 mg kg-1 capsaicin significantly reduced the Evans blue extravasation induced by hot water at 50 degrees C and 60 degrees C, whereas guanethidine pretreatment 24 h before the experiment caused a significantly increased response at 40 degrees C, 45 degrees C and 50 degrees C. When Evans blue was injected between 10 and 120 min after immersion of the paw in hot water, a significant extravasation of the dye was no longer detectable. However, the weight of the paw as well as the weight of the piece of skin taken for Evans blue quantification increased during this period indicating the progressive development of oedema in the skin and underlying tissues. In rats treated with capsaicin as neonates, the increase in paw weight after immersion in water of 50 degrees C for 5 min was significantly delayed during the first hour, but there was no difference after two hours. In rats pretreated with D-Arg1,D-Pro2-,D- Trp7 ,9, Leu11 -substance P, a substance P (SP) antagonist, the Evans blue extravasation was significantly reduced. However, the response, which remained in rats treated with capsaicin as neonates was not blocked by the SP-antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)     

AM404, an anandamide transport inhibitor, reduces plasma extravasation in a model of neuropathic pain in rat: role for cannabinoid receptors

Neuropathic pain consequent to peripheral nerve injury has been associated with local inflammation. Following noxious stimulation afferent fibres release substance P (SP) and calcitonin-gene related peptide (CGRP), which are closely related to oedema formation and plasma leakage. The effect of the anandamide transport blocker AM404 has been studied on plasma extravasation after chronic constriction injury (CCI) which consists in a unilateral loose ligation of the rat sciatic nerve (Bennett and Xie, 1988). AM404 (1-3-10 mg kg(-1)) reduced plasma extravasation in the legated paw, measured as mug of Evans Blue per gram of fresh tissue. A strong effect on vascular permeability was also produced by the synthetic cannabinoid agonist WIN 55,212-2 (0.1-0.3-1 mg kg(-1)). Using specific antagonists or enzyme inhibitors, we demonstrate that cannabinoids act at several levels: data on the 3rd day suggest a strong involvement of substance P (SP) and calcitonin gene-related peptide (CGRP) in the control of vascular tone, whereas at the 7th and 14th days the major role seems to be played by prostaglandins (PGs) and nitric oxide (NO). Capsaicin injection in ligated paws of AM404- or WIN 55,212-2-treated rats resulted in an increase of Evans Blue extravasation, suggesting the involvement of the cannabinergic system in the protective effect of C fibres of ligated paws. Taken together, these data demonstrate the efficacy of cannabinoids in controlling pain behaviour through the modulation of several pain mediators and markers of vascular reactivity, such as SP, CGRP, PGs and NO.     

Effects of the orally active non-peptide bradykinin B2 receptor antagonist, FR173657, on plasma extravasation in guinea pig airways

We investigated the effect of the orally active non-peptide bradykinin B2 receptor antagonist, FR173657 (E)-3-(6-acetamido-3-pyridyl)-N-[N-[2.4-di-chloro-3-[(2-methyl-8-quinoli nyl)oxymethyl]phenyl]-N-methy-laminocarbonylmethyl] acrylamide), on plasma extravasation mediated by activation of sensory nerves in guinea pig airways. Plasma extravasation was assessed by the photometric measurement of the extravasated Evans blue after formamide extraction. We found that the increase in Evans blue dye extravasation evoked by an aerosol of bradykinin (0.1 mM, 2 min) in the presence of phosphoramidon (2.5 mg/kg, i.v.) was abolished completely by FR173657 (20 mg/kg, p.o.) in the trachea and main bronchi. In sensitized guinea pigs pretreated with phosphoramidon, FR173657 (20 mg/kg, p.o.) inhibited plasma extravasation evoked by ovalbumin aerosol (5%, 2 min) by 77+/-14.2% in the trachea and 65+/-11.2% in the main bronchi. FR173657 (20 mg/kg, p.o.) did not affect the plasma extravasation caused by aerosolised capsaicin. These findings suggest that FR173657 is an orally active, promising anti-inflammatory agent for kinin-dependent inflammation following antigen challenge.     

An examination of neurogenic mechanisms involved in mustard oil-induced inflammation in the mouse

The mechanisms by which topical mustard oil causes vasodilatation in the mouse were investigated using the tachykinin NK1 receptor antagonist SR140333 and the calcitonin gene-related peptide (CGRP) antagonist BIBN4096BS, alongside alphaCGRP or NK1 receptor knockout mice. Blood flow was assessed by laser Doppler flowmetry and plasma extravasation by 125I-albumin accumulation. Mustard oil produced significant plasma extravasation and vasodilatation in wild type mice, although the plasma extravasation was less than that seen with capsaicin whilst the vasodilatation was greater. The plasma extravasation was abolished in tachykinin NK1 knockout mice, whilst the vasodilatation was enhanced. BIBN4096BS was unable to inhibit the vasodilatation in wild type mice but abolished it in the NK1 knockout mice. In alphaCGRP knockout mice, mustard oil also caused plasma extravasation and vasodilatation, which were both inhibited by treatment with SR140333. These data suggest that both a tachykinin NK1 receptor agonist and a CGRP agonist are active as vasodilators, producing redundancy, requiring blockade of both mediators to prevent vasodilatation.     

Inhibition by viozan of extravasation induced in rat trachea by capsaicin is mediated exclusively by β2-adrenoceptors

The mechanism by which 2(3H)-benzothiazolone, 4-hydroxy-7-[2-[[2-[[3-(2-phenylethoxy)propyl]-sulphonyl]ethyl]amino]ethyl]-monohydrochloride (AR-C68397AA; viozan), a dual dopamine D2/beta2-adrenoceptor agonist which has shown promise in the treatment of chronic obstructive pulmonary disease (COPD), inhibits the extravasation of plasma protein induced by capsaicin in the tracheas of Brown Norway rats has been re-evaluated. Viozan (10-30 microg/kg given intratracheally; i.t.) inhibited dose-dependently the extravasation of plasma protein tagged with Evans Blue into rat trachea induced by capsaicin (10 microg/kg i.t.). Similar effects were seen with the selective beta2-adrenoceptor agonist, salbutamol (3-10 microg/kg i.t.), but the selective dopamine D2 receptor agonist, quinagolide (10-30 microg/kg i.t.), was inactive. The effects of viozan and salbutamol were abolished by propranolol (3 mg/kg) given intraperitoneally (i.p.) but unaffected by sulpiride (3 mg/kg i.p.). Thus, in c,ontrast to claims in the literature, a functional response to dopamine D2 receptor activation in a preclinical model of oedema arising from sensory nerve fibre activation in the rat lung could not be demonstrated. Moreover, no qualitative difference could be demonstrated between the response to a dual D2/beta2-adrenoceptor agonist and a selective beta2-adrenoceptor agonist. The observations call into question whether a dual D2/beta2-adrenoceptor agonist such as viozan would bring added benefit over established selective beta2-adrenoceptor agonists in the therapy