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1. Nerve growth factor induces an airway hyperresponsiveness in vivo in guinea-pigs, as we have shown previously. Since antagonizing the neurokinin-1 (NK(1)) receptor can prevent this NGF-induced airway hyperresponsiveness and since sensory nerves release tachykinins, we investigated the role of sensory nerves in the NGF-induced airway hyperresponsiveness. 2. We used isolated tracheal rings from guinea-pigs to measure tracheal contractility. In these rings sensory nerve endings are present, but these endings lack any contact with their cell bodies. 3. In this in vitro system, NGF dose-dependently induced a tracheal hyperresponsiveness to histamine. The NK(1) receptor antagonist SR140333 could block the induction of tracheal hyperresponsiveness. 4. To further investigate the involvement of sensory nerve endings we used the cannabinoid receptor 1 (CB(1)) agonist R-methanandamide to inhibit excitatory events at the nerve terminal. The CB(1) receptor agonist was capable of blocking the tracheal hyperresponsiveness to NGF in the isolated system, as well as the airway hyperresponsiveness to NGF in vivo. 5. This indicates that NGF can induce an increase in airway responsiveness in the absence of sensory nerve cell bodies. NGF may act by increasing substance P release from sensory nerve endings, without upregulation of substance P in the neurons. Substance P in its turn is responsible for the induction of the NGF-induced airway hyperresponsiveness.

1. The contribution of reactive nitrogen species to the development of airway hyperresponsiveness in a mouse model of allergic inflammation was investigated by the use of selective inhibitors of nitric oxide and superoxide formation. 2. Sensitized mice, repeatedly challenged with ovalbumin showed a significant (P<0.001, n=9) increase in airway responsiveness measured using whole body plethysmography. This hyperresponsiveness was accompanied by an influx of eosinophils into the airway lumen and increased levels of ovalbumin-specific serum IgE. 3. Treatment of mice with the iNOS inhibitor 1400 W or the NADPH-oxidase inhibitor apocynin did not significantly alter cellular influx into the airway lumen nor serum ovalbumin specific IgE. In contrast, apocynin as well as 1400 W inhibited ovalbumin-induced airway hyperresponsiveness (P<0.001 and P<0.05 respectively, n=9). Furthermore, the airways of allergen challenged animals showed clear 3-nitrotyrosine staining, which was mainly located in eosinophils. Remarkably, treatment with apocynin or 1400 W did not alter 3-nitrotyrosine staining. 4. These data suggest that the development of airway hyperresponsiveness during the airway inflammation upon ovalbumin challenge is dependent on the release of both superoxide and nitric oxide and is therefore likely to be dependent on reactive nitrogen species. This mechanism, however, is not reflected by 3-nitrotyrosine formation in the airways.

1. Motor responses to des-Arg9-bradykinin and bradykinin were studied in the isolated mouse trachea (precontracted with carbachol, 10 microM) and the urinary bladder of either Swiss, C57B1/6J or bradykinin B2 receptor knockout (Bk2r(-/-)) mice after 1-6 h in vitro. The expression of mRNA for the mouse B1 receptor in tracheal and urinary bladder tissues was also studied by using Northern blot analysis. 2. In isolated tracheae, des-Arg9-bradykinin produced a relaxant response that increased over time: no response was observed after 1 h of incubation, whereas after 6 h the maximum response (1 microM) was 68-84% of the relaxation produced by isoproterenol (1 microM) in the three mouse strains. The relaxant response to bradykinin (1 microM) observed at 1 h (38-51% of isoproterenol) was increased (62-65% of isoproterenol) after 6 h in Swiss and C57B1/6J mice, but was absent in Bk2r(-/-) mice. In the presence of cycloheximide, des-Arg9-bradykinin did not cause any response at 6 h. 3. Similar findings were obtained in the urinary bladder: at 1 h des-Arg9-bradykinin (1 microM) did not cause any motor effect, whereas at 6 h it caused a contraction that was 28-59% of that produced by carbachol (1 microM) in the three mouse strains. Cycloheximide blocked the response to des-Arg9-bradykinin. Bradykinin (1 microM) contracted urinary bladders at 1 h (34-35% of carbachol), as well as at 6 h (66-77% of carbachol) in Swiss and C57B1/6J strains, but was without effect in Bk2r(-/-) mice. 4. Northern blot hybridization with a specific cDNA probe against mouse B1 receptor mRNA using total RNA extracted from tracheae and urinary bladders freshly removed from Swiss and Bk2r(-/-) mice revealed minimal expression. However, marked hybridization was detected 150 min after in vitro exposure in both tissues. 5. Evidence is provided that in vitro exposure of mouse trachea and urinary bladder causes a time-dependent induction of B1 receptors that cause relaxation and contraction, respectively.

1. The endothelin (ET) receptor subtype that mediates niric oxide (NO)-dependent airway relaxation in tracheal tube preparations precontracted with carbachol and pretreated with indomethacin was investigated. The release of NO induced by ET from guinea-pig trachea using a recently developed porphyrinic microsensor was also measured. 2. ET-1 (1 pM-100 nM) contracted tracheal tube preparations pretreated with the NO-synthase inhibitor, L-NMMA, and relaxed, in an epithelium-dependent manner, preparations pretreated with the inactive enantiomer D-NMMA. The effect of L-NMMA was reversed by L-Arg, but not by D-Arg. 3. The selective ET(B) receptor agonists, IRL 1620 or sarafotoxin S6c, both (1 pM-100 nM) contracted tracheal tube preparations in a similar manner either after treatment with D-NMMA or with L-NMMA. In the presence of the ET(A) receptor antagonist, FR139317 (10 microM), ET-1 administration resulted in a contraction that was similar after either L-NMMA or D-NMMA. In the presence of the ET(B) receptor antagonist, BQ788 (1 microM), ET-1 relaxed and contracted tracheas pretreated with D-NMMA and L-NMMA, respectively. 4. Exposure of tracheal segments to ET-1 (1-1000 nM) caused a concentration-dependent increase in NO release that was reduced by L-NMMA. IRL1620 (1 microM) did not cause any significant NO release. FR139317 (10 microM), but not, BQ788 (1 microM), inhibited the NO release induced by ET-1. 5. These results demonstrate that in the isolated guinea-pig trachea activation of ET(B) receptors results in a contractile response, whereas activation of ET(A) receptors cause both a contraction, and an epithelium-dependent relaxation that is mediated by NO release.

1. Mice were sensitized by 7 intraperitoneal injections of ovalbumin without adjuvant (10 micrograms in 0.5 ml of sterile saline) on alternate days and after 3 weeks exposed to either ovalbumin (2 mg ml-1 in sterile saline) or saline aerosol for 5 min on 8 consecutive days. One day before the first challenge, animals were injected intraperitoneally on a daily basis with vehicle (0.25 ml sterile saline), dexamethasone (0.5 mg kg-1) or metyrapone (30 mg kg-1). 2. In vehicle-treated ovalbumin-sensitized animals ovalbumin challenge induced a significant increase of airway responsiveness to metacholine both in vitro (27%, P < 0.05) and in vivo (40%, P < 0.05) compared to saline-challenged mice. Virtually no eosinophils could be detected after saline challenge, whereas the numbers of eosinophils were significantly increased (P < 0.01) at both 3 and 24 h after the last ovalbumin challenge (5.48 +/- 3.8 x 10(3) and 9.13 +/- 1.7 x 10(3) cells, respectively). Furthermore, a significant increase in ovalbumin-specific immunoglobulin E level (583 +/- 103 units ml-1, P < 0.05) was observed after ovalbumin challenge compared to saline challenge (201 +/- 38 units ml-1). 3. Plasma corticosterone level was significantly reduced (-92%, P < 0.001) after treatment with metyrapone. Treatment with metyrapone significantly increased eosinophil infiltration (17.4 +/- 9.93 x 10(3) and 18.7 +/- 2.57 x 10(3) cells, P < 0.05 at 3 h and 24 h, respectively) and potentiated airway hyperresponsiveness to methacholine compared to vehicle-treated ovalbumin-challenged animals. Dexamethasone inhibited both in vitro and in vivo hyperresponsiveness as well as antigen-induced infiltration of eosinophils (0, P < 0.05 and 0.7 +/- 0.33 x 10(3) cells, P < 0.05 at 3 h and 24 h, respectively). Metyrapone as well as dexamethasone did not affect the increase in ovalbumin-specific immunoglobulin E levels after ovalbumin challenge (565 +/- 70 units/ml-1; P < 0.05; 552 +/- 48 units ml-1, P < 0.05 respectively). 4. From these data it can be concluded that exogenously applied corticosteroids can inhibit eosinophil infiltration as well as airway hyperresponsiveness. Vise versa, endogenously produced corticosteroids play a down-regulating role on the induction of both eosinophil infiltration and airway hyperresponsiveness.

1. Recently, we developed a murine model to investigate toluene diisocyanate (%DI)-induced occupational asthma. After skin-sensitization and intranasal challenge with TDI (1%) mice exhibited tracheal hyperreactivity 24 h after the challenge. 2. The aim of the present study was to investigate the possible role for sensory neuropeptides in the development of this tracheal hyperreactivity. 3. First, we demonstrated that direct application of TDI in vitro induced the release of tachykinins from the sensory nerves in the mouse isolated trachea. Second, capsaicin pretreatment, resulting in the depletion of sensory neuropeptides, completely abolished the TDI-induced tracheal hyperreactivity 24 h after the challenge. Third, the selective neurokinin1 (NK1)-receptor antagonist RP 67580 (0.2 mumol kg-1) also inhibited tracheal hyperreactivity when it was administered before the challenge. However, administration of RP 67580 during the sensitization phase did not result in a suppression of the TDI-induced tracheal hyperreactivity 24 after the challenge. 4. When TDI-sensitized mice were topically challenged with TDI a marked ear swelling response was observed. The cutaneous response after TDI application was not affected by capsaicin pretreatment or RP 67580 administration. 5. These results clearly show that sensory neuropeptides, particularly tachykinins, are essential for the development of TDI-induced tracheal hyperreactivity during the effector phase. The differences between the airways and skin with respect to the sensory neuropeptides is intriguing and could suggest a local action for the tachykinins in the airways.

1. Sodium nitroprusside (SNP) completely relaxed the guinea-pig isolated, perfused trachea in a concentration-dependent manner. Although SNP was less potent by about 2 orders of magnitude, its maximal effect was 25% higher compared to isoprenaline. 2. SNP (3.2 microM) increased cyclic GMP levels by 300% and relaxed guinea-pig isolated, perfused trachea by 54%. The SNP-induced relaxations of the preparations were not affected by the guanylate cyclase inhibitor, methylene blue. Moreover, zaprinast, a cyclic GMP-specific phosphodiesterase inhibitor which was supposed to enhance SNP-induced relaxations, decreased the maximal relaxation by 22% (P < 0.001). 3. In contrast, 8Br-cyclic GMP (10 microM) increased the cyclic GMP levels by 1100% without inducing a marked relaxation. 4. SNP (10 microM) and S-nitroso-N-acetylpenicillamine (SNAP; a direct donor of nitric oxide; 10 microM), relaxed the tissues by 75% and 25%, respectively, without any nitric oxide (NO) release by SNP (< 1 pmol 100 microliters-1), but a substantial NO release by SNAP (560 pmol 100 microliters-1). 5. It is concluded that the SNP-induced tracheal relaxations are probably not mediated by cyclic GMP and NO.

1. An experimental set up is used whereby the serosal (out)side or mucosal (in)side of the guinea-pig isolated tracheal tube can be stimulated selectively with drugs and reactivity measured. 2. Potassium induces a concentration-dependent (5-70 mM) monophasic contraction of tracheal tubes when added on the outside. In contrast, on the inside, potassium induces a concentration-dependent relaxation at low concentrations (5-40 mM) which was reversed into a contraction up to approximately basal tone at higher concentrations (50-70 mM). 3. Epithelium denudation reversed the potassium-induced relaxation into a contraction. Interestingly, in the 'half' epithelium-denuded trachea the contractions were significantly (P < 0.01) reduced by 46% compared to complete epithelium-denuded tissues. 4. Incubation with the nitric oxide (NO) synthase inhibitor N omega-nitro-L-arginine methyl ester (L-NAME, 120 microM) for 30 min on the inside of the tracheal tube completely prevented the relaxation. However, L-NAME did not reverse the potassium-induced relaxation into a contraction. This indicates that potassium does not penetrate through the epithelial layer. 5. It is concluded that depolarization of smooth muscle cells leads to a monophasic contraction and that depolarization of the epithelium leads to a relaxation of tracheal smooth muscle. The epithelial layer has an important barrier function and can release relaxing factors like NO.

1. We investigated whether virus-induced airway hyperresponsiveness in guinea-pigs could be modulated by pretreatment with capsaicin and whether viral respiratory infections could potentiate ovalbumin-aerosol-induced tracheal hyperresponsiveness. 2. Animals were inoculated intratracheally with bovine parainfluenza-3 virus or control medium 7 days after treatment with capsaicin (50 mg kg-1, s.c.). Four days after inoculation, tracheal contractions were measured to increasing concentrations of substance P, histamine and the cholinoceptor agonist, arecoline. 3. In tracheae from virus-infected guinea-pigs, contractions in response to substance P, histamine and arecoline were significantly enhanced (P < 0.01) by 144%, 46% and 77%, respectively. Capsaicin pretreatment inhibited the hyperresponsiveness to substance P partly (62%) and to histamine and arecoline completely. 4. In another series of experiments animals were first sensitized with ovalbumin (20 mg kg-1, i.p.). After 14 days animals were exposed to either saline or ovalbumin aerosols for 8 days. After 4 aerosol exposures (4 days) animals were inoculated with either parainfluenza-3 virus or control medium. One day after the last ovalbumin aerosol, tracheal contraction in response to increasing concentrations of substance P, histamine and arecoline was measured. 5. Tracheae from ovalbumin-aerosol-exposed control inoculated animals showed a similar degree of airway hyperresponsiveness to saline-aerosol-exposed virus-treated guinea-pigs. Virus inoculation of ovalbumin-treated animals significantly potentiated the tracheal contractions to substance P compared to either of the treatments alone. The contractions in response to histamine and arecoline were only slightly enhanced. 6. In conclusion, sensory nerves and/or tachykinins are involved in virus-induced airway hyperresponsivenessin guinea-pigs and viral respiratory infections can potentiate the increase in tracheal responsiveness to bronchoconstrictor agonists after ovalbumin exposure.

1. The effect of 13-hydroxylinoleic acid (13-HODE) on changes in blood pressure in the rat was measured. 2. 13-HODE (0.1 - 100 micrograms kg-1) had no direct effect on blood pressure in the rat and had no effect on histamine (0.1 - 1000 micrograms kg-1)-induced changes in blood pressure. In contrast, it was found that 13-HODE itself induced a decrease in diastolic arterial blood pressure when it was injected intravenously after either a single dose of histamine (10, 100 or 1000 micrograms kg-1) or after a dose-response curve of histamine (0.1 - 1000 micrograms kg-1). 3. This hypotensive effect of 13-HODE was not observed after administration of the endothelium-dependent vasodilator, acetylcholine (0.1 - 10 micrograms kg-1), the endothelium-independent vasodilator, sodium nitroprusside (0.1 - 100 micrograms kg-1) or the inflammatory mediator, leukotriene B4 (0.1 - 300 micrograms kg-1). However, prior injection of bradykinin (0.1 - 100 micrograms kg-1) allowed a dose-dependent hypotensive effect of 13-HODE to be revealed. 4. The hypotensive effect of 13-HODE after histamine and bradykinin could be inhibited by neonatal capsaicin treatment of the rats (50 mg kg-1, s.c. on day 1 and 2 after birth). 5. Ruthenium red (120 micrograms kg-1 min-1), an inhibitor of excitatory effects on sensory nerves, and the CGRP antagonist, CGRP8-37 (1-3 micrograms kg-1 min-1) also inhibited the hypotensive effect of 13-HODE. 6. It is concluded that the hypotensive effect of 13-HODE in the rat after histamine and bradykinin is due to the release of a CGRP-like substance from sensory nerves. These results highlight the possibility that endogenous 13-HODE could be involved in the neurogenic regulation of blood pressure.

1. This study investigates the effects of capsaicin-induced depletion of sensory neuropeptides and of neurokinin1 (NK1) receptor blockade on delayed-type hypersensitivity (DTH)-induced changes of vascular permeability in the small intestine of the mouse. 2. The DTH reaction in the small intestine was elicited by dinitrofluorobenzene (DNFB)-contact sensitization followed by oral dinitrobenzene sulphonic acid (DNBS) challenge. To assess vascular leakage the accumulation of the plasma marker, Evans blue (EB), was measured 2, 24 and 48 h after the challenge. 3. The small intestinal DTH reaction was characterized by a significant increase in vascular permeability 24 h after the challenge of previously sensitized mice when compared to vehicle-sensitized mice (P < 0.05, ANOVA). Capsaicin-induced depletion of sensory neuropeptides, two weeks before the sensitization, completely inhibited the DTH-induced increase in small intestinal vascular permeability at 24 h (P < 0.05, ANOVA). Vehicle/control: 108.2 +/- 8.6 ng EB mg-1 dry weight; vehicle/DTH 207.8 +/- 25.1 ng EB mg-1 dry weight; capsaicin/control: 65.8 +/- 11.9 ng EB mg-1 dry weight; capsaicin/DTH: 84.3 +/- 7.6 ng EB mg-1 dry weight. 4. The tachykinins, substance P and neurokinin A (1.5 to 50 x 10(-11) mol per mouse, i.v.), induced an increase in vascular leakage in the small intestine of naive mice. The specific NK1 receptor antagonist, RP67580 (10(-9) mol per mouse, i.v.) was the most effective in reducing the substance P-induced plasma extravasation when compared with other NK receptor antagonists, FK224 and FK888. 5. Treatment of DNFB-sensitized mice with RP67580 (10-9 mol per mouse, i.v.) immediately before and 1 h after the DNBS challenge resulted in a significant reduction of the DTH-induced increase in vascular permeability at 24 h (vehicle/control: 107.5 +/- 8.8 ng EB mg-1 dry weight; RP67580/control:95.4 +/- 5.4 ng EB mg-1 dry weight; vehicle/DTH: 206.6 +/- 22.6 ng EB mg-1 dry weight; RP67580/DTH:132.6 +/- 13.6 ng EB mg-1 dry weight, P<0.05, ANOVA).6. These results suggest that sensory nerves are involved in the development of small intestinal DTH reactions in the mouse. NK1 receptors could play an important role in the initiation of the DTH-induced changes in vascular leakage.

1. The circulation of natural killer (NK) cells in vivo is influenced by physical exercise, mental stress, and infusion of beta-adrenoceptor agonists. We have previously presented in vitro data, showing that beta 2-adrenoceptor agonists induce detachment of NK cells from endothelial cells (EC), supporting the hypothesis that NK cells can be recruited from the marginating pool in blood vessels. 2. Because NK cells as well as EC express beta 2-adrenoceptors, the present study was conducted to investigate whether stimulation of the beta-adrenoceptors on NK cells, EC or both cell types is required to induce detachment from EC. 3. Cells were pretreated (15 min) with a selective beta 2-adrenoceptor antagonist, GR81706, at various concentrations. The duration of beta-adrenoceptor blockade was tested by determining the adenosine 3',5'-cyclic monophosphate (cyclic AMP) production induced by terbutaline (a beta 2-adrenoceptor specific agonist). This receptor-mediated response was effectively inhibited for at least 4 h, whereas the cyclic AMP production in response to forskolin (a direct activator of adenylate-cyclase) was not affected. 4. Functional adhesion assays were then performed to determine the role of beta-adrenoceptors on the different cell types involved (NK and EC) in catecholamine-induced detachment. Peripheral blood mononuclear cells were allowed to adhere for 1 h to monolayers of unstimulated EC in the presence or absence of cyclic AMP inducing agents, and the percentage of NK cells in the adhering lymphocyte fraction was determined by flow cytometry. 5. Both adrenaline (10(-5) M) and forskolin (10(-5) M) caused detachment of NK cells from EC. After blockade of the P2-adrenoceptors on NK cells by pretreatment with GR81706 (10-6 M), the effect of adrenaline on NK cells adhesion was pretented; after blockade of the beta2-adrenoceptors on EC, NK cell adhesion was still significantly reduced by adrenaline. In all cases, forskolin caused detachment of NKcells.6. To establish further that stimulation of beta-adrenoceptors on NK cells is sufficient to cause detachment,we showed that adrenaline also reduced adhesion of NK cells to monolayers of Chinese hamster ovary cells, which do not express beta-adrenoceptors.7. Together, these results show that stimulation of beta2-adrenoceptors on NK cells negatively influences their capacity to adhere to EC, and that beta2-adrenoceptors on EC play a negligible role in this phenomenon.

1. The endothelium plays a critical role in maintaining vascular tone via generation of potent vasoconstrictor and dilator substances. We examined the effect of bovine purified polymorphonuclear leukocytes (PMN) on the endothelium-dependent relaxation to acetylcholine in isolated mesenteric arteries. 2. In the presence of PMN (2.5 x 10(6) cells ml-1) the maximal relaxation to acetylcholine was decreased from 76.1 +/- 2.4% to 44.9 +/- 7.4% of the precontraction (P < 0.001). This effect was inhibited by superoxide dismutase and NG-mono-methyl-L-arginine, but not by catalase or indomethacin. 3. PMN were not able to influence significantly the endothelium-independent relaxation to nitroprusside. 4. Removal of PMN after preincubation and prior to precontraction and relaxation did not influence the acetylcholine-induced relaxation, indicating that no irreversible vascular damage had occurred. 5. Superoxide anion production by unstimulated PMN was less than 10% compared to phorbol myristate acetate-activated PMN, measured by chemiluminescence and reduction of ferricytochrome c. 6. We conclude that small amounts of superoxide anions produced by unstimulated PMN contribute to a decrease in relaxation to acetylcholine by interfering with endothelium-derived nitric oxide.

1. The effects of muscarinic receptor antagonists considered to be selective for M1 receptors (pirenzepine; PZ), M2 receptors (AFDX-116), and for M3 receptors (4-diphenyl acetoxy N-methyl-piperidine (4-DAMP)) were used to investigate the existence of muscarinic receptors subtypes in murine airways. Atropine was used as a nonselective antagonist. The effects of these antagonists were studied upon tracheal contractions induced either by EFS (electric field stimulation) or by application of an exogenous cholinoceptor agonist (arecoline). 2. The muscarinic receptor antagonists tested inhibited arecoline-induced tracheal contractions with the following rank order of potency: 4-DAMP = atropine > pirenzepine = AFDX-116. The rank order of potency of the muscarinic antagonists used in inhibiting EFS-induced tracheal contractions was: 4-DAMP = atropine > PZ > AFDX-116. The pA2 values for these antagonists were similar when compared to the pA2 values determined in guinea-pig and bovine airway smooth muscle. 3. In addition to in vitro studies, the effects of inhalation of the different muscarinic antagonists on lung function parameters in vivo were investigated. Inhalation of 4-DAMP induced a decrease in airway resistance and an increase in lung compliance. In contrast, inhalation of AFDX-116 induced an increase in airway resistance and almost no change in lung compliance. Apart from some minor effects of atropine on airway resistance, atropine, PZ, and pilocarpine failed to induce changes in lung mechanics as determined by in vivo lung function measurements. 4. The results provide evidence for the existence of M3 receptors on murine tracheae that are involved in the contraction of tracheal smooth muscle. This is in agreement with other animal species such as the guinea-pig and bovine. In vivo experiments also demonstrated that in the mouse, M3 receptors play an important role in bronchial smooth muscle contraction and thus in bronchoconstriction. Interestingly we have also demonstrated that M2 receptors can play a role in bronchodilatation. Inhalation of an M2 receptor antagonist induced an increase in airway resistance whereas inhalation of an M3 receptor antagonist induced a decrease in airway resistance. It is therefore likely that an M3/M2 receptor balance plays an important role in the regulation of airway function.

1. Guinea-pig tracheal contractions by histamine and by the cholinoceptor agonist, arecoline, are significantly enhanced (30% and 20%, respectively), 96 h after intra-tracheal inoculation with Parainfluenza-3 (PI-3) virus. 2. The airway hyperresponsiveness in animals inoculated with virus coincides with a significant increase in the number of broncho-alveolar cells (82%), and in the albumin concentration (121%) in lung lavage fluid, relative to values obtained in guinea-pigs challenged with control solution. 3. The chemiluminescence production by isolated broncho-alveolar cells, obtained from virus-infected guinea-pigs 96 h after inoculation stimulated with PI-3 virus in vitro, is significantly reduced by 42% relative to broncho-alveolar cells obtained from animals inoculated with control solution. This diminution was not specific for stimulation by PI-3 virus since the chemiluminescence production was also significantly reduced by 30% in response to zymosan. 4. Pretreatment of the guinea-pigs with the anti-allergic drugs, oxatomide (2.5 mg kg-1) or nedocromil (2.5 mg kg-1), or the specific H1-histamine receptor antagonist, levocabastine (0.25 mg kg-1), administered intra-peritoneally twice a day for five successive days, inhibits the virus-induced airway hyperresponsiveness, suppresses the influx of broncho-alveolar cells and increase in albumin content, and corrects the reduced chemiluminescence production by broncho-alveolar cells in response to zymosan. 5. In contrast, the cyclo-oxygenase inhibitor, suprofen (5.0 mg kg-1), the 5-HT2 receptor antagonist, ketanserin (0.63 mg kg-1), or the Ca2+ overload blocker, flunarizine (2.5 mg kg-1) do not modify the above mentioned processes. 6. The platelet-activating factor receptor antagonist, WEB 2170 (10 mg kg-1), reduces virus-induced airway hyperresponsiveness and influx of broncho-alveolar cells into the lungs but does not attenuate the increase of albumin in the bronchial lavage fluid. 7. Guinea-pigs nebulized with histamine, twice a day (30 min) during 4 successive days, do not demonstrate an increased airway responsiveness, but instead show tachyphylaxis in response to histamine in vitro. In addition, no influx of inflammatory cells is found in these animals. 8. These results suggest that histamine does not directly increase the responsiveness of the guinea-pig trachea; however, histamine may be involved in a cascade of events leading to airway hyperresponsiveness after a viral infection, a process that could be related to an influx and/or an activation of broncho-alveolar cells after PI-3 virus stimulation.

1. [3H]-prazosin homogeneously labels alpha 1-adrenoceptors in guinea-pig cerebral cortex and rat spleen membranes with dissociation constants of 1.28 and 1.49 x 10(-10) M respectively. 2. Phentolamine and WB 4101 displacement studies show that guinea-pig cerebral cortex contains 30% alpha 1A- and 70% alpha 1B-adrenoceptor subtypes, whereas rat spleen contains a virtually homogeneous alpha 1B-adrenoceptor subtype population. The alpha 1-adrenoceptor population of rat thoracic aorta is predominantly of the alpha 1A-adrenoceptor subtype, and in guinea-pig thoracic aorta it is mainly of the alpha 1B-adrenoceptor subtype. 3. Half of the compounds displacing [3H]-prazosin bound to guinea-pig cerebral cortex membranes display alpha 1A-adrenoceptor selectivity. Among these compounds, WB 4101 and methoxamine are most selective, displaying selectivity ratios of approximately 38 and approximately 26 respectively. 4. The affinity constants of the non-selective compounds for the alpha 1-adrenoceptor in guinea-pig cerebral cortex membranes correlate well with the affinity constants obtained for alpha 1B-adrenoceptors in rat spleen membranes. The affinities of selective compounds for the alpha 1B-adrenoceptor subtype in guinea-pig cerebral cortex correlate very well with their affinity for alpha 1B-adrenoceptor in the rat spleen homogenate. Both regression lines coincide with the line of identity. The affinity constants of selective compounds for the alpha 1A-adrenoceptors in guinea-pig cerebral cortex only apparently correlate with the affinity for either the alpha 1B-adrenoceptors in guinea-pig cerebral cortex or in the rat spleen. Regression analyses indicate a straight line relationship (r2>0.9) between pKEA and Pk1B but the regression lines deviate from the line of identity.

1. The effects of polymorphonuclear leukocytes (PMN) on vascular function to (-)-noradrenaline were examined in vitro. Purified bovine PMN were incubated in siliconized organ baths containing rings of bovine mesenteric arteries, after which a concentration-effect curve in response to (-)-noradrenaline was obtained. 2. PMN-derived products induced a long lasting concentration-dependent contraction of the blood vessels generating 24.4 +/- 6.8% of the maximal tension to (-)-noradrenaline at a cell concentration of 2.5 x 10(6) ml-1. The contractile response was also found in endothelium-denuded vascular rings. 3. PMN present in the organ bath caused an increase in the sensitivity of vascular rings to (-)-noradrenaline. At a cell number of 2.5 x 10(6) PMN ml-1 the pD2-value for (-)-noradrenaline was augmented 0.40 +/- 0.05 (P less than 0.001), while total contraction at the highest concentration (-)-noradrenaline was not affected. This increase in sensitivity was dependent on an intact endothelium. 4. The increase in sensitivity to (-)-noradrenaline by PMN was inhibited by superoxide dismutase, but not by catalase, dimethylthiourea, indomethacin or nordihydroguaiaretic acid. The non-stimulated bovine PMN produced oxygen radicals as measured by chemiluminescence. 5. Simultaneous incubation of PMN and (-)-noradrenaline with arterial rings induced an increase in the release of prostacyclin, measured by an elevated concentration of 6-keto-prostaglandin F1 alpha in the supernatant. 6. It is concluded that PMN can increase vascular tone directly or indirectly probably via the interaction of PMN-derived superoxide anions with endothelium-derived relaxing factor.

1. It has been shown that opioid peptides modulate airway function. In the present study, the effect of beta-endorphin on antigen-induced contractions of isolated tracheal rings from actively sensitized guinea-pigs has been studied. 2. beta-Endorphin had a concentration-dependent bimodal effect on anaphylactic contractions of the trachea. Low concentrations of beta-endorphin (10(-10) and 10(-8) M) significantly potentiated anaphylactic contractions, whereas higher concentrations (10(-7) and 10(-6) M) significantly suppressed anaphylactic contractions of guinea-pig trachea. 3. beta-Endorphin in concentrations of 10(-8) M and 10(-7) M did not affect the responsiveness of the tracheal rings to histamine or leukotriene D4. This indicates that beta-endorphin does not influence the responsiveness of tracheal smooth muscle to anaphylactic mediators. 4. In the presence of the non-selective opioid receptor antagonist naloxone, 10(-8) M beta-endorphin still potentiated the anaphylactic contractions of the trachea. In addition, an equimolar concentration of des-Tyr1-beta-endorphin, a fragment of beta-endorphin without opioid-like activity, also potentiated anaphylactic contractions. The potentiation of anaphylactic contraction by 10(-8) M beta-endorphin is not therefore mediated by classical opioid-receptors. 5. In the presence of naloxone, 10(-7) M, beta-endorphin did not suppress anaphylactic contractions of the trachea. Thus, the suppression of anaphylactic contraction is mediated via a classical opioid-receptor. 6. In epithelium-denuded trachea, both 10(-8) and 10(-7) M beta-endorphin suppressed the anaphylactic contractions, whereas 10(-8) and 10(-7) M des-Tyr1-beta-endorphin did not affect anaphylactic contractions. It is concluded that the potentiation of the anaphylactic contraction in intact trachea is epithelium-dependent whereas the suppression of the anaphylactic contraction is epithelium-independent.

Administration to guinea-pigs of 15-hydroperoxy-arachidonic acid (0.2 mg kg-1 i.p.) caused a 20% reduction of lung beta-adrenoceptor number. Furthermore, in vivo, a hyperreactivity of the airways to nebulized histamine was observed. In contrast, administration of 15-hydroxy-arachidonic acid (0.2 mg kg-1 i.p.) did not cause a significant change in either of these parameters.

1 In renal hypertensive rats (one-clip, two-kidney type) blood pressure returned to a normotensive level within 24 h after the removal of the renal artery clip (unclipping). 2 The decrease in blood pressure caused by intravenous administration of arachidonic acid, prostaglandin E2 and prostaglandin I2 was significantly reduced in these unclipped rats. 3 The hypotensive response to bradykinin and acetylcholine was the same in unclipped rats and in control rats. 4 Nephrectomy abolished the difference in blood pressure response to arachidonic acid and the two prostaglandins between unclipped and control rats. 5 An enhanced secretion of renin, as indicated by the absence of an increase in plasma renin activity, did not seem to be involved in the attenuated blood pressure response to arachidonic acid in unclipped rats.

1 A simple double-isotope assay for phospholipase A2 activity of perfused organs is described; Guinea-pig lungs perfused through the pulmonary circulation exhibit a low background enzyme activity. This activity is blocked by dexamethasone, betamethasone and hydrocortisone, mepacrine, procaine or chlorpromazine. Aspirin and indomethacin are without effect. 3 Mechanical trauma, antigen challenge or injections of bradykinin, rabbit aorta contracting substance-releasing factor (RCS-RF) or histamine increase "basal" phospholipase activity. The effect of these agents, except that of bradykinin, is blocked by dexamethasone or mepacrine. 4 The blocking effect of steroids is cumulative and dose-dependent. They do not work in cell-free systems. Inhibition by mepacrine is rapid and is effective in cell-free lung homogenates. 5 It is suggested that agents which liberate prostaglandin endoperoxides and thromboxane A2 from perfused lungs do so by activating phospholipase A2.

1. In the present study the effects of anterior hypothalamic (AHA) lesions and sham-operations were investigated on the endotoxin-induced airway hyperreactivity in guinea-pigs. Unoperated, sham-operated and AHA-lesioned guinea-pigs were injected intraperitoneally with Escherichia coli endotoxin and the airway reactivity tested four days later in isolated tracheal spirals and in spontaneously breathing anaesthetized animals. Control animals were given sterile saline. 2. Sham-operated control animals demonstrated a diminished responsiveness of the tracheal spirals in vitro and of the lung resistance (delta R1) in vivo to histamine receptor and cholinoceptor-muscarinic agonists as compared to unoperated control animals. 3. AHA-lesioned control animals showed a responsiveness of the respiratory airways in vitro and in vivo between the values of unoperated and sham-operated control animals, suggesting that lesions partially restored the diminished responsiveness. 4. In unoperated and sham-operated guinea-pigs, endotoxin administration induced hyperreactivity of the tracheal spirals and delta R1 to histamine receptor and cholinoceptor-muscarinic agonists with respect to the control groups. 5. In AHA-lesioned animals, the endotoxin-induced airway hyperreactivity in vitro and in vivo to histamine receptor and cholinoceptor-muscarinic agonists was absent.