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PubMed1993

Involvement of neurogenic inflammation in antigen-induced bronchoconstriction in guinea pigs.

The role of tachykinins released from sensory nerves in bronchoconstriction induced by antigen was studied in sensitized guinea pigs anesthetized with pentobarbital sodium and pretreated with atropine. The combination of NK2 (SR-48968) and NK1 (CP-96,345) tachykinin-receptor antagonists abolished the increase in total pulmonary resistance (RL) evoked by intravenous capsaicin but did not affect the response evoked by intravenous histamine. A small dose of aerosolized ovalbumin (OVA, 0.1%) produced a small increase in RL that was further increased and markedly prolonged by the neutral endopeptidase (NEP) inhibitor phosphoramidon; this bronchoconstrictor effect of OVA was markedly reduced by the NK2-receptor antagonist and was abolished by the combination of the NK1 and NK2-receptor antagonists together. When a larger dose of OVA (0.5%) was used, a maximal bronchoconstrictor response was obtained. Phosphoramidon did not potentiate this response significantly. The combination of NK1- and NK2-receptor antagonists blunted the response at 5 min only slightly but markedly attenuated the later (10-20 min) response. These results show that tachykinins released from sensory nerves play a significant role in antigen-induced bronchoconstriction in guinea pigs. This effect is exaggerated when the normal modulation of neuropeptides by NEP is inhibited and is mediated predominantly by NK2-receptor activation, with a smaller contribution by NK1 receptors.

Aerosols↗

PubMed1994

Adenosine receptor-mediated bronchoconstriction and bronchial hyperresponsiveness in allergic rabbit model.

Recently, there has been an increasing interest in adenosine as a potential mediator of allergic asthma. In the present study, we have employed an allergic rabbit model of late-phase asthma to characterize the adenosine receptor subtype in the asthmatic airways. The allergic rabbit model has physiological characteristics and pharmacological sensitivity comparable to human asthma. Adenosine causes a dose-dependent bronchoconstriction in allergic, but not in normal, rabbits. This adenosine-induced bronchoconstriction is significantly inhibited by theophylline, an adenosine receptor antagonist, thus suggesting the involvement of adenosine receptor(s). 5'-(N-ethylcarboxyamido) adenosine (NECA), a nonselective agonist, 2-[p-(2-carboxyethyl)-phenethylamino]-5'-(N-ethylcarboxamido)-aden osine (CGS-21680), an A2-selective receptor agonist, and cyclopentyl adenosine (CPA), an A1-selective agonist, were used to characterize the adenosine receptor subtype in the airways of allergic rabbits, respectively. The PC50 (concentration of agonist in mg/ml required to reduce the dynamic compliance 50% from the baseline) values for adenosine, CGS-21680, NECA, and CPA were 9.25 +/- 0.86, 6.8 +/- 0.69, 3.90 +/- 0.27, and 1.45 +/- 0.26 mg/ml, respectively. Thus the potency profile for the bronchoconstrictor of adenosine in this model is a typical A1-receptor subtype (CPA > NECA > CGS-21680 > adenosine). Adenosine also induced further bronchial hyperresponsiveness (BHR) at 1 but not at 24 h following aerosol challenge.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗

PubMed1993

Oxygen radicals in bronchoconstriction of guinea pigs elicited by isocapnic hyperpnea.

The role of oxygen radicals in isocapnic hyperpnea-induced bronchoconstriction (HIB) of guinea pigs was investigated using scavengers of the radicals. In series 1, 50 young guinea pigs were randomly divided into seven groups: control 1, control 2, chlorisondamine, tetrodotoxin (TTX), acute dimethylthiourea (DMTU), tachykinin depletion, and 5% CO2 in air. Animals of the control 2 group received vehicle (saline) infusion while those of the control 1 group did not. Chlorisondamine was used to block ganglionic transmission, TTX to interrupt nerve conduction, DMTU to scavenge hydroxyl radicals, and chronic capsaicin pretreatment to deplete tachykinins. The animals in the last group were ventilated with dry 5% CO2 in air during hyperpnea. In series 2, 13 additional animals were used to test the effects of intratracheal administration of superoxide dismutase and catalase (SOD + CAT) on HIB. Each animal was anesthetized with pentobarbital sodium, cannulated with a tracheal cannula and venous catheter, paralyzed with gallamine triethiodide, and mechanically ventilated. During the baseline period, each animal was ventilated normally with humidified air. Then it was hyperventilated 15 min with a dry gas mixture of 95% O2-5% CO2, except animals in the last group of series 1. Subsequently, all animals returned to normal ventilation with humidified air for 45 min (recovery period). The maximal expiratory flow and dynamic compliance were obtained periodically during the recovery period. The isocapnic hyperpnea using 95% O2-5% CO2, but not 5% CO2 in air, caused bronchoconstriction that was significantly blocked by acute DMTU, acute SOD + CAT, and tachykinin depletion. In an additional group of six animals, acute DMTU did not significantly alter acetylcholine-induced airway constriction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Morphometry of methacholine-induced bronchoconstriction in the rat.

It has been suggested that parenchymal viscoelasticity accounts for a large proportion of resistive pressure losses induced by smooth muscle agonists. We used morphometric methods to evaluate the relative contributions of parenchyma and airways to mechanical changes during methacholine- (MCh) induced bronchoconstriction. We measured tracheal pressure and tidal volume in 17 open-chest mechanically ventilated Sprague-Dawley rats (frequency = 1.5 Hz, tidal volume = 2 ml, positive end-expiratory pressure = 5 cmH2O) after saline (n = 7, C), 16 mg/ml MCh (n = 5, L), and 256 mg/ml MCh (n = 5, H) aerosols. We calculated pulmonary resistance (RL) and elastance (EL) by fitting the equation PL = VRL + VEL + K, where PL is transpulmonary pressure, V is flow, and V is volume. V was obtained numerically from V. Lungs were rapidly frozen in liquid N2 30 s after aerosolization and processed with freeze substitution. Using midsagittal slices of left lung, we measured airway narrowing as the ratio of lumen area (aBM) subtended by the basement membrane perimeter (LBM) to predicted maximal lumen area (ABM = LBM2/4 pi). Air space size was estimated as mean linear intercept (Lm) and parenchymal distortion as standard deviation of linear intercepts (SDi). Lm was increased in L and H animals, reflecting hyperinflation; aBM/ABM in 0.17- to 0.43-mm-diam airways decreased progressively from C to L to H animals, reflecting bronchoconstriction. By use of stepwise multiple linear regression, the contribution of Lm to variance in mechanics was found to consistently exceed or equal that of aBM/ABM. SDi contributed little once Lm was taken into account.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerosols↗

PubMed1995

Repeated measurement of respiratory function and bronchoconstriction in unanesthetized mice.

A noninvasive forced oscillation technique was used to determine respiratory function in unanesthetized and spontaneously breathing mice. Pseudorandom noise pressure variations in a frequency range of 16-208 Hz were applied to the body surface, and the flow response was measured at the nose. From the pressure-flow relationship, respiratory transfer impedance was calculated. Study of intra-animal variability on a short- and a long-term basis revealed that the real part of respiratory transfer impedance was reproducible within 9%. The imaginary part appeared less reproducible (within 22%). Furthermore, bronchoconstrictive responses were investigated and analyzed by evaluation of respiratory resistance as measured at 16 Hz (Rrs16). During the first 15 min after ovalbumin challenge in ovalbumin-sensitized mice, Rrs16 was significantly increased [49 +/- 7% (SE)]. Inhalation of methacholine in untreated mice induced an increase in Rrs16 of 75 +/- 16% (SE). In saline-challenged animals, no significant changes were observed. This method enables evaluation of long-term respiratory function in mice and appeared to be a sensitive measure for bronchoconstriction.

Administration, Inhalation↗

PubMed1996

Methacholine-induced bronchoconstriction and airway smooth muscle in the guinea pig.

We examined the role of airway smooth muscle (ASM) as a determinant of the site and extent of methacholine (MCh)-induced airway narrowing in anesthetized and mechanically ventilated guinea pigs. The sites of airway narrowing and ASM were determined in animals (n = 4) bronchoconstricted to 75, 60, 40, or 15% of the maximal lung resistance (RL,max) induced by aerosolized MCh and compared with a saline-challenged animal. The median luminal area of each animal was significantly inversely correlated to the percentage of RL,max (r = -0.95; P < 0.01). However, there was no correlation between the degree of narrowing of any given airway and the quantity of ASM of any given airway. The relationship between the amount of ASM and responsiveness to MCh was studied in different animals (n = 13). The range of the concentration of MCh required to reach 50% of RL,max (EC50) varied by 254-fold, but the RL,max had only a 3.6-fold range. There was no correlation between RL,max and ASM. However, there was a correlation between the log EC50 and ASM (r = -0.541; P<0.05) in intraparenchymal cartilaginous airways. In conclusion, morphometric measurements of airway narrowing are correlated with pulmonary resistance. Variability in the quantity of ASM does not appear to be a determinant of the heterogeneity of airway narrowing or of maximal bronchoconstriction among normal guinea pigs. However, the sensitivity to MCh is associated with differences in the amount of ASM in intraparenchymal cartilaginous airways.

Airway Resistance↗

PubMed1996

Eicosanoids modulate hyperpnea-induced bronchoconstriction in canine peripheral airways.

We examined the role of leukotrienes (LTs) in the development of dry air-induced bronchoconstriction (AIB) in canine peripheral airways. Airway reactivity to exogenous LTs was first tested by using an LTD4 aerosol challenge: peripheral airway resistance increased approximately 130 +/- 51% (n = 4) above baseline when compared with its vehicle control. AIB was then assessed by measuring peripheral airway resistance after, and airway wall temperature during, a dry air challenge (DAC). Treatment with a peptidoleukotriene biosynthesis inhibitor (MK-0591) attenuated AIB by approximately 65% without altering airway wall temperature. The fact that MK-0591 did not alter airway reactivity to aerosolized acetylcholine and completely inhibited Ca2+ ionophore-induced LTB4 generation in canine whole blood attests to the specificity of the drug. Treatment with MK-0591 did not affect the increased number of epithelial cells recovered in bronchoalveolar lavage fluid 5 min after DAC. Concentrations of LTs and other eicosanoids in bronchoalveolar lavage fluid from vehicle-treated DAC airways were increased above baseline values; only LTs were reduced by MK-0591. Before MK-0591, AIB was significantly correlated with the dry air-induced generation of LTC4, LTD4, and LTE4. After treatment with MK-0591, AIB was correlated with thromboxane B2, prostaglandin (PG) F2 alpha, and PGE2. We conclude that hyperpnea with dry air stimulates local production and release of LTs in canine bronchi and, alone with the generation of bronchoconstricting and bronchodilating PGs, plays a central role in the modulation of AIB.

Animals↗

PubMed1997

Temporal dynamics of acute isovolume bronchoconstriction in the rat.

The time course of lung impedance changes after intravenous injection of bronchial agonist have produced significant insights into the mechanisms of bronchoconstriction in the dog (J. H. T. Bates, A.-M. Lauzon, G. S. Dechman, G. N. Maksym, and T. F. Shuessler. J. Appl. Physiol. 76: 616-626, 1994). We studied the time course of acute induced bronchoconstriction in five anesthetized paralyzed open-chest rats injected intravenously with a bolus of methacholine. For the 16 s immediately after injection, we held the lung volume constant while applying small-amplitude flow oscillations at 1.48, 5.45, and 19.69 Hz simultaneously, which provided us with continuous estimates of lung resistance (RL) and elastance (EL) at each frequency. This procedure was repeated at initial lung inflation pressures of 0.2, 0.4, and 0.6 kPa. Both RL and EL increased progressively after methacholine administration; however, the rate of change of EL increased dramatically as frequency was increased, whereas RL remained relatively independent of frequency. We interpret these findings in terms of a three-compartment model of the rat lung, featuring two parallel alveolar compartments feeding into a central airway compartment. Model simulations support the notions that both central airway shunting and regional ventilation inhomogeneity developed to a significant degree in our constricted rats. We also found that the rates of increase in both RL and EL were greatly enhanced as the initial lung inflation pressure was reduced, in accord with the notion that parenchymal tethering is an important mechanism limiting the extent to which airways can narrow when their smooth muscle is stimulated to contract.

Airway Resistance↗

PubMed1997

ET-1-induced bronchoconstriction is mediated via ETB receptor in mice.

Endothelin (ET)-1 is one of the most potent agonists of airway smooth muscle and can act via two different ET receptor subtypes, i.e., ETA and ETB. To determine the effects of ET-1 on in vivo pulmonary function and which ET receptors are involved in murine lungs, we investigated 1) the effects of ET and sarafotoxin S6c (S6c), a selective ETB agonist, on pulmonary function and 2) the effects of BQ-123 and BQ-788, specific ETA- and ETB-receptor antagonists, on ET-1-induced bronchoconstriction. ICR mice were anesthetized and mechanically ventilated (frequency = 2.5 Hz, tidal volume = 8 ml/kg, positive end-expiratory pressure = 3 cmH2O). Intravenous ET-1, ET-2, and ET-3 increased lung resistance similarly and equipotently, whereas S6c elicited a greater degree of bronchoconstriction. Mice were then pretreated with saline (Sal), BQ-123 (0.2, 1, and 5 mg/kg), or BQ-788 (0.2, 1, and 5 mg/kg) before administration of ET-1 (10(-7) mol/kg iv). No dose of BQ-123 blocked ET-1-induced constriction, whereas pretreatment with each dose of BQ-788 significantly inhibited ET-1-induced responses. There were significant differences in morphometrically assessed airway constriction between Sal and BQ-788 and between BQ-123 and BQ-788, whereas no significant difference was observed between Sal and BQ-123. There were no significant morphometric differences in the airway wall area among the three groups. These observations suggest that the ETB- but not ETA-receptor subtype may mediate the changes in murine pulmonary function in response to ET-1. In addition, the ETB-receptor antagonist reduces ET-1-induced airway narrowing by affecting airway smooth muscle contraction in mice.

Animals↗

PubMed1999

Mucosal injury and eicosanoid kinetics during hyperventilation-induced bronchoconstriction.

Bronchoalveolar lavage (BAL) of canine peripheral airways was performed at various times after hyperventilation, and BAL fluid (BALF) cell and mediator data were used to evaluate two hypotheses: 1) hyperventilation-induced mucosal injury stimulates mediator production, and 2) mucosal damage is correlated with the magnitude of hyperventilation-induced bronchoconstriction. We found that epithelial cells increased in BALF immediately after a 2- and a 5-min dry air challenge (DAC). Prostaglandins D(2) and F(2alpha) and thromboxane B(2) were unchanged immediately after a 2-min DAC but were significantly increased after a 5-min DAC. Leukotriene C(4), D(4), and E(4) did not increase until 5 min after DAC. Hyperventilation with warm moist air did not alter BALF cells or mediators and caused less airway obstruction that occurred earlier than DAC. BALF epithelial cells were correlated with mediator release, and mediator release and epithelial cells were correlated with hyperventilation-induced bronchoconstriction. These observations are consistent with the hypothesis that hyperventilation-induced mucosal damage initiates peripheral airway constriction via the release of biochemical mediators.

Airway Resistance↗

PubMed2001

Airway resistance and tissue elastance from input or transfer impedance in bronchoconstricted monkeys.

Ascaris suum (AS) challenge in nonhuman primates is used as an animal model of human asthma. The primary goal of this study was to determine whether the airways and respiratory tissues in monkeys that are bronchoconstricted by AS inhalation behave similarly to those in asthmatic humans. Airway resistance (Raw) and tissue elastance (Eti) were estimated from respiratory system input (Zin) or transfer (Ztr) impedance. Zin (0.4-20 Hz) and Ztr (2-128 Hz) were measured in anesthetized cynomolgus monkeys (n = 10) under baseline (BL) and post-AS challenge conditions. Our results indicate that AS challenge in monkeys produces 1) predominantly an increase in Raw and not tissue resistance, 2) airway wall shunting at higher AS doses, and 3) heterogeneous airway constriction resulting in a decrease of lung parenchyma effective compliance. We investigated whether the airway and tissue properties estimated from Zin and Ztr were similar and found that Raw estimated from Zin and Ztr were correlated [r(2) = 0.76], not significantly different at BL (13.6 +/- 1.4 and 13.1 +/- 0.9 cmH(2)O. l(-1). s(-1), respectively), but significantly different post-AS (20.5 +/- 4.5 cmH(2)O. l(-1). s(-1) and 18.5 +/- 5.2 cmH(2)O. l(-1). s(-1)). There was no correlation between Eti estimated from Zin and Ztr. The changes in lung mechanical properties in AS-bronchoconstricted monkeys are similar to those recently reported in human asthma, confirming that this is a reasonable model of human asthma.

Airway Resistance↗

PubMed2002

Handgrip-induced airway dilation in asthmatic patients with bronchoconstriction induced by MCh inhalation.

We investigated the effects of static and rhythmic handgrip on the time course of recovery of airway resistance measured with the interrupter technique (Rint) following bronchoconstriction induced by methacholine (MCh) inhalation in 17 asthmatic patients. On three separate occasions, a 100 +/- 5% increase in baseline Rint was induced by MCh inhalation. Subsequently, patients either rested [control trials (CTs)] or performed 3-min bouts of static or rhythmic handgrip. Respiratory and cardiovascular variables were continuously monitored. Rint changes were assessed at 1-min intervals for 30 min after rest and both types of handgrip. Plasma catecholamine concentrations were also determined at scheduled intervals. Bronchoconstriction increased ventilation (P < 0.01) but did not affect cardiovascular variables and plasma catecholamine concentrations. Handgrip provoked an increase in cardiovascular variables (P < 0.01) and plasma norepinephrine concentrations (P < 0.05) but caused no additional changes in ventilation. Rint only partially recovered within 30 min after CTs, whereas it consistently decreased 1 min after both handgrip paradigms and remained lower than after CTs (P always <0.01) for the whole 30-min observation period. Sympathetic activation and withdrawal of cholinergic input to the airway smooth muscle reflexly induced by activation of skeletal muscle and carotid sinus receptors may be the primary events accounting for the bronchodilator response induced by handgrip. Mediators co-released in response to sympathetic activation may also have contributed.

Administration, Inhalation↗

PubMed2005

Separation of bronchoconstriction from increased ventilatory drive in a nonhuman primate model of chronic allergic asthma.

The relationship between allergen-induced ventilatory drive and bronchoconstriction was investigated in dust mite-sensitive cynomolgus macaques periodically exposed to low doses of aerosolized antigen for up to 5.5 yr. Initially, the animals responded to aerosolized dust mite allergen at a concentration of 350 arbitrary units (AU)/ml with simultaneous increases in lung resistance (RL) and respiratory rate (RR). With time, RL and RR became differentially sensitive to allergen provocation. At the end of the study period, aerosolized allergen at a concentration of 15 AU/ml doubled RR without increasing RL. When mechanically ventilated to maintain tidal volume, higher concentrations of allergen could be delivered, and RL increased. Inhaled disodium cromoglycate and intravenous diphenhydramine attenuated the increase in RR, indicating that allergen-induced release of histamine and activation of H(1) receptors mediated the response. Inhaled beta-adrenergic agonists attenuated the RR response to dust mite and to direct histamine provocation. These results demonstrate that chronic periodic allergen challenge increases the allergic sensitivity of histamine-dependent reflexes controlling ventilatory drive. Activation of these reflexes is independent of overt bronchoconstriction, but can be inhibited by beta-adrenergic agonists, indicating that beta-adrenergic agonists exert their effect independent of bronchodilation.

Animals↗

PubMed2004

Effects of posture and bronchoconstriction on low-frequency input and transfer impedances in humans.

We simultaneously evaluated the mechanical response of the total respiratory system, lung, and chest wall to changes in posture and to bronchoconstriction. We synthesized the optimal ventilation waveform (OVW) approach, which simultaneously provides ventilation and multifrequency forcing, with optoelectronic plethysmography (OEP) to measure chest wall flow globally and locally. We applied an OVW containing six frequencies from 0.156 to 4.6 Hz to the mouth of six healthy men in the seated and supine positions, before and after methacholine challenge. We measured mouth, esophageal, and transpulmonary pressures, airway flow by pneumotachometry, and total chest wall, pulmonary rib cage, and abdominal volumes by OEP. We computed total respiratory, lung, and chest wall input impedances and the total and regional transfer impedances (Ztr). These data were appropriately sensitive to changes in posture, showing added resistance in supine vs. seated position. The Ztr were also highly sensitive to lung constriction, more so than input impedance, as the former is minimally distorted by shunting of flow into alveolar gas compression and airway walls. Local impedances show that, during bronchoconstriction and at typical breathing frequencies, the contribution of the abdomen becomes amplified relative to the rib cage. A similar redistribution occurs when passing from seated to supine. These data suggest that the OEP-OVW approach for measuring Ztr could noninvasively track important lung and respiratory conditions, even in subjects who cannot cooperate. Applications might range from routine evaluation of airway hyperreactivity in asthmatic subjects to critical conditions in the supine position during mechanical ventilation.

Adult↗

PubMed2004

Attenuation of induced bronchoconstriction in healthy subjects: effects of breathing depth.

The effects of breathing depth in attenuating induced bronchoconstriction were studied in 12 healthy subjects. On four separate, randomized occasions, the depth of a series of five breaths taken soon (approximately 1 min) after methacholine (MCh) inhalation was varied from spontaneous tidal volume to lung volumes terminating at approximately 80, approximately 90, and 100% of total lung capacity (TLC). Partial forced expiratory flow at 40% of control forced vital capacity (V(part)) and residual volume (RV) were measured at control and again at 2, 7, and 11 min after MCh. The decrease in V(part) and the increase in RV were significantly less when the depth of the five-breath series was progressively increased (P < 0.001), with a linear relationship. The attenuating effects of deep breaths of any amplitude were significantly greater on RV than V(part) (P < 0.01) and lasted as long as 11 min, despite a slight decrease with time when the end-inspiratory lung volume was 100% of TLC. In conclusion, in healthy subjects exposed to MCh, a series of breaths of different depth up to TLC caused a progressive and sustained attenuation of bronchoconstriction. The effects of the depth of the five-breath series were more evident on the RV than on V(part), likely due to the different mechanisms that regulate airway closure and expiratory flow limitation.

Adult↗

PubMed2002

Noninvasive measurement of midexpiratory flow indicates bronchoconstriction in allergic rats.

This study was designed to evaluate the value and applicability of tidal breathing pattern analysis to assess bronchoconstriction in conscious rats. Using noninvasive, head-out body plethysmography and the decrease in tidal midexpiratory flow (EF(50)), we measured airway responsiveness (AR) to inhaled acetylcholine and allergen in conscious Brown-Norway rats, followed by invasive determination of pulmonary conductance (GL) and EF(50) in anesthetized rats. Dose-response studies to acetylcholine showed that noninvasively recorded EF(50) closely reflected the dose-dependent decreases observed with the invasive monitoring of simultaneously measured GL and EF(50). After sensitization and intratracheal boost to ovalbumin or saline, rats were assessed for early and late AR to aerosolized ovalbumin. Ovalbumin aerosol challenge resulted in early and late AR in allergen-sensitized rats, whereas controls were unresponsive. The allergen-specific AR, as measured noninvasively by EF(50), was similar in degree compared with invasively recorded EF(50) and GL and was associated with enhanced IgE and airway inflammation. We conclude that EF(50) is a noninvasive and physiologically valid index of bronchoconstriction in a rat model of asthma.

Acetylcholine↗

PubMed2005

Brain stem excitatory and inhibitory signaling pathways regulating bronchoconstrictive responses.

This review summarizes recent work on two basic processes of central nervous system (CNS) control of cholinergic outflow to the airways: 1) transmission of bronchoconstrictive signals from the airways to the airway-related vagal preganglionic neurons (AVPNs) and 2) regulation of AVPN responses to excitatory inputs by central GABAergic inhibitory pathways. In addition, the autocrine-paracrine modulation of AVPNs is briefly discussed. CNS influences on the tracheobronchopulmonary system are transmitted via AVPNs, whose discharge depends on the balance between excitatory and inhibitory impulses that they receive. Alterations in this equilibrium may lead to dramatic functional changes. Recent findings indicate that excitatory signals arising from bronchopulmonary afferents and/or the peripheral chemosensory system activate second-order neurons within the nucleus of the solitary tract (NTS), via a glutamate-AMPA signaling pathway. These neurons, using the same neurotransmitter-receptor unit, transmit information to the AVPNs, which in turn convey the central command to airway effector organs: smooth muscle, submucosal secretory glands, and the vasculature, through intramural ganglionic neurons. The strength and duration of reflex-induced bronchoconstriction is modulated by GABAergic-inhibitory inputs and autocrine-paracrine controlling mechanisms. Downregulation of GABAergic inhibitory influences may result in a shift from inhibitory to excitatory drive that may lead to increased excitability of AVPNs, heightened airway responsiveness, and sustained narrowing of the airways. Hence a better understanding of these normal and altered central neural circuits and mechanisms could potentially improve the design of therapeutic interventions and the treatment of airway obstructive diseases.

Animals↗

PubMed1992

Preventive effects of inhaled formoterol and salbutamol on histamine-induced bronchoconstriction--a placebo-controlled study.

The preventive effects of inhaled formoterol (a new beta 2-agonist) and salbutamol aerosols on histamine-induced bronchoconstriction were studied in 12 patients with mild or moderate asthma in a placebo-controlled, double-blind study. Three hours after the administration of 12 micrograms formoterol, 200 micrograms salbutamol (doses with equal bronchodilator effects) or placebo via aerosol, histamine challenge was undertaken, using a dosimetric jet nebulizer with controlled tidal breathing. The noncumulative dose of histamine diphosphate aerosol provoking a 15% fall in FEV1 (PD15) was calculated. The PD15 after inhalation of 12 micrograms formoterol was significantly higher than that after 200 micrograms salbutamol (median values 640 and 310 micrograms, respectively; p < 0.01). For both treatments, the PD15 was significantly higher than that after placebo (median 185 micrograms). The results indicate that the preventive effect against histamine-induced bronchoconstriction at 3 h after drug is significantly better with formoterol than with salbutamol when using inhaled doses with an equal acute bronchodilator effect.

Administration, Inhalation↗