Beta-adrenergic blockade in ponies with recurrent obstructive pulmonary disease

Ponies with recurrent airway obstruction have hyperresponsive airways during acute disease exacerbations but not during clinical remission. We examined the effect of beta-adrenergic blockade with propranolol on airway responsiveness to aerosol histamine in six ponies with recurrent airway obstruction and six age- and gender-matched controls. Measurements were made with principal ponies in clinical remission (period A) and during an acute period of airway obstruction (period B). beta-Adrenergic blockade did not change airway responsiveness, dynamic compliance (Cdyn), or pulmonary resistance (RL) in either group of ponies at period A or in the control ponies at period B. In principal ponies at period B, propranolol significantly increased RL but was without effect on Cdyn or airway responsiveness. We conclude that the beta-adrenergic system is involved in the control of central airway caliber in principal ponies at period B but that this system does not seem to be involved in the mechanism of airway hyperresponsiveness to histamine.     

Airway reactivity in ponies with recurrent airway obstruction (heaves)

We measured lung function and airway reactivity to histamine administered by aerosol in two groups of ponies. Principal ponies had a history of heaves, a disease characterized by recurrent airway obstruction when ponies are housed in a barn and fed hay; control ponies had no history of airway obstruction. Ponies were paired (principal and control) and measurements were made when principal ponies were at pasture and in clinical remission (period A), following barn housing when principal ponies had acute airway obstruction (period B), and after a further 1 and 2 wk at pasture (periods C and D). At periods A, C, and D dynamic compliance (Cdyn), pulmonary resistance (RL), arterial O2 tension (PaO2), and CO2 tension (PaCO2) of principals and controls did not differ. Barn housing (period B) decreased Cdyn and PaO2 and increased RL in principals but not controls. The ED65Cdyn (the dose of histamine to reduce Cdyn to 65% of base line) did not differ in principals and controls at periods A, C, and D. At period B, ED65Cdyn decreased by 2.5-log doses of histamine in principals while ED65Cdyn was not affected in controls. There was no correlation between changes in airway reactivity and changes in RL and Cdyn. We conclude that ponies in clinical remission from heaves are not hyperreactive to histamine aerosol. This model of lung disease is similar to some forms of industrial asthma in which hyperreactivity occurs only during acute airway obstruction. The lack of correlation between ED65Cdyn and the degree of airway obstruction suggests that the hyperreactivity of principal ponies to histamine aerosol cannot be explained solely by alterations in baseline airway caliber.     

Effects of atropine in ponies with recurrent airway obstruction

The effects of atropine on lung function and airway reactivity in two groups of ponies were measured. Principal ponies had a history of recurrent airway obstruction when housed in a barn and fed hay; control ponies had no history of airway obstruction. Principal and control ponies were paired, and measurements were made when principal ponies were in clinical remission (period A) and during an acute attack of airway obstruction (period B). Atropine did not alter pulmonary resistance (RL), dynamic compliance (Cdyn), or airway responsiveness in either group of ponies at period A or in the controls at period B. In principal ponies at period B, atropine did not alter Cdyn or the concentration of aerosol histamine required to decrease Cdyn to 65% of base line (ED65Cdyn) but reduced RL and the change in RL induced by 0.1 mg/ml histamine (delta RL0.1). It is likely that the latter observation was due to geometric changes in the airways, because the change in RL and in delta RL0.1 were significantly correlated. The results of this study show little resting bronchomotor tone in normal ponies, but a major portion of the increase in RL in principals at period B is mediated via muscarinic receptors. Little evidence exists for muscarinic receptor involvement in the response to aerosol histamine in either principal or control ponies.     

Effects of aerosol histamine and carbachol on central and peripheral airflow resistance in sheep

Sixteen anesthetized artificially ventilated open-chest sheep were prepared with retrograde catheters to allow for measurement of dynamic compliance of the lungs (Cdyn), total airflow resistance of the lungs (RL), and central (Rc) and peripheral (Rp) airflow resistance. Twelve sheep received aerosol histamine and 12 sheep received aerosol carbachol. Eight sheep received and responded to both aerosol histamine and aerosol carbachol. Three sheep received both aerosol histamine and aerosol carbachol but failed to respond to both agents. Under base-line conditions, for the 16 sheep, 69% of total RL was located in the peripheral component, Rp, and 31% in the central component, Rc. Aerosol histamine caused only peripheral small airway changes while aerosol carbachol predominantly effected the central large airways. When aerosol histamine responsiveness, defined using Cdyn or Rp, was compared to aerosol carbachol responsiveness using Rc, a correlation was demonstrable (r = 0.84, n = 8, P less than 0.05). It is possible in sheep to cause relatively pure peripheral small airway and relatively pure central large airway changes by using different bronchoconstrictor agents. Aerosol histamine and aerosol carbachol responsiveness correlated with each other in these artificially ventilated anesthetized sheep.     

Evaluation of the mechanism of decreased airway responsiveness in lambs

In this study we investigated three possible mechanisms for the decreased airway responsiveness (AR) found in young lambs. To evaluate aerosol delivery, 6 adult sheep (9 mo-3 yr old) and 12 lambs (4-8 wk old) were challenged with aerosol (aH) and intravenous histamine (ivH). Awake animals were intubated and studied in a plethysmograph, which measured dynamic compliance (Cdyn), resistance of the lung, and functional residual capacity. AR to histamine was measured by administration of increasing concentrations of histamine until a significant change in lung mechanics occurred or until the maximum dose of histamine was given. In all six adult sheep, the response to both aH and iVH was a decrease in Cdyn. In two lambs Cdyn was decreased with both aH and ivH, in five lambs with neither, in three lambs with aH only, and in two lambs with ivH only. To examine the role of beta-adrenergic activity in determining AR, six adult sheep and six lambs received ivH and on a separate day ivH with propranolol pretreatment (p + ivH). The median effective dose of histamine that caused a reduction in Cdyn to 65% of normal saline control (ED65Cdyn) for the adult sheep given ivH was 3.60 (range 0.23-4.85) and 0.70 (range 0.49-8.0) micrograms.kg-1.min-1 for p + ivH (P = NS). The median ED65Cdyn for the six lambs was 8.0 micrograms.kg-1.min-1 for both ivH alone and p + ivH. To evaluate the role of airway smooth muscle (SM), AR to aH was quantitated in six adult sheep and six lambs, and then an open-lung biopsy was performed.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vivo PAF-induced airway eosinophil accumulation reduces bronchial responsiveness to inhaled histamine

Chronic eosinophilic bronchitis and bronchial hyperresponsiveness have been considered to be the fundamental features of bronchial asthma. However, the role of airway eosinophils in bronchial responsiveness in vivo has not been fully discussed. The aim of this study was to investigate the direct effect of airway eosinophil accumulation on bronchial responsiveness in vivo. Guinea pigs were transnasally treated with platelet activating factor (PAF) or vehicle twice a week for a total of 3 weeks. Anesthetized guinea pigs were surgically cannulated and artificially ventilated 48 h after the last administration of PAF or vehicle. Ten minutes after the installation of artificial ventilation, ascending doses of histamine were inhaled. In a subsequent study, selective inhibitors of diamine oxidase and histamine N-methyltransferase were intravenously administered before the histamine inhalation in the PAF-treated animals. Next study was conducted 20 min after treatment with indomethacin in this study line. Finally, ascending doses of methacholine were inhaled in our animal model. Proportion of eosinophils and the number of nuclear segmentation in bronchoalveolar lavage fluid significantly increased in guinea pigs treated with PAF compared with vehicle and this finding was confirmed histologically. Nevertheless, bronchial responsiveness to inhaled histamine, but not methacholine, was significantly decreased by the PAF treatment. This bronchoprotective effect induced by PAF remained following aminoguanidine and histamine N-methyltransferase administration, but abolished by treatment of indomethacin. These results suggest that in vivo airway eosinophils may reduce nonspecific bronchial responsiveness through production of inhibitory or bronchoprotective prostanoids, but not through histaminase production.     

Prostaglandin F2 alpha increases responsiveness of pulmonary airways in dogs

We studied the effect of prostaglandin F2 alpha (PGF2 alpha) on the responsiveness of pulmonary airways in dogs. Airway responsiveness was assessed by determining the bronchoconstrictor response to increasing concentrations of acetylcholine aerosol delivered to the airways. In each of five dogs, we determined responsiveness during treatment with physiologic saline, histamine, or PGF2 alpha aerosols. The doses of histamine and PGF2 alpha were determined by establishing the largest dose of each which could be given to the dog without causing bronchoconstriction (subthreshold doses). We found that airway responsiveness was not significantly different during histamine treatment than after saline, however, responsiveness increased during treatment with PGF2 alpha. In addition, the hyperresponsiveness induced by PGF2 alpha was prevented by pretreatment with the ganglion blocking drug hexamethonium (5 mg/kg given intravenously). The results show that PGF2 alpha specifically increases the responsiveness of pulmonary airways in doses that do not cause bronchoconstriction, and suggest that the hyperresponsiveness involves a neural mechanism such as increased responsiveness of airway sensory nerves.     

Tachyphylaxis to inhaled aerosolized histamine in anesthetized dogs

Three consecutive dose-response curves to inhaled aerosolized histamine, separated by 1-h intervals, were obtained in 20 anesthetized mongrel dogs. In general, successive histamine dose-response curves shifted progressively rightward. Changes in pulmonary resistance (RL) and dynamic compliance (Cdyn) in response to low concentrations of histamine were reproducible, but responses to high concentrations (sufficient to at least double RL or decrease Cdyn by at least 30%) decreased on successive dose-response curves. The concentration of histamine required to double RL increased significantly (P less than 0.05) from 1.01 mg/ml on the first to 1.62 and 2.02 mg/ml on the second and third dose-response curves. In contrast, consecutive methacholine dose-response curves were not significantly different. Indomethacin pretreatment (5 mg/kg iv) prevented histamine tachyphylaxis, whereas atropine (4 mg iv) did not. However, indomethacin did not alter base-line pulmonary mechanics or histamine responsiveness as measured on the first dose-response curve. We conclude that tachyphylaxis to inhaled aerosolized histamine occurs in anesthetized dogs. Our results are consistent with an important role for endogenous prostaglandins in modulating the airway responses to repeated histamine exposures.     

Effects of pulmonary congestion on airway reactivity to histamine aerosol in dogs

We examined the effect of acute pulmonary vascular congestion on bronchial reactivity in dogs in a standard challenge protocol. Airway responsiveness to histamine whose concentration was varied in a stepwise incremental fashion was assessed from changes in pulmonary resistance (RL) and dynamic compliance (Cdyn) in 10 anesthetized dogs. Brief acute pulmonary congestion was created by inflating a balloon placed in the left atrium to raise left atrial pressure to 20-30 cmH2O for 1 min. Pulmonary congestion did not change RL in the control condition. However, after histamine inhalation, RL was further increased by pulmonary congestion, making the two effects synergistic. This phenomenon could not be observed with vagi cut. Pulmonary congestion decreased Cdyn in all dogs regardless of histamine concentration, with or without vagotomy. We conclude that pulmonary vascular congestion makes the bronchi hyperreactive through vagal reflexes. The reduction in Cdyn caused by pulmonary congestion appears to stem mainly from the narrowing of peripheral airways by adjacent vascular engorgement.     

Distribution of pulmonary responsiveness to aerosol histamine in dogs

Dose-response curves to aerosol histamine in 102 anesthetized, intubated, spontaneously breathing dogs revealed a spectrum of airway responsiveness with a greater than 40-fold difference between the most and the least sensitive animals. The frequency distribution of responses fits a log normal distribution. No correlation was found between sex, age, or control values of dynamic compliance (Cdyn) and lung resistance (RL) and the dose of histamine required to cause a response. Repetitive studies in 17 dogs observed for up to 20 mo showed that the dose at which an individual dog would respond was reproducible within a narrow range and that the differences between dogs were highly significant (P greater than 0.001). The long-term reproducibility of the response to aerosol histamine in individual dogs suggests that short-term reversible airway insults are not responsible for the range in responses noted between animals.     

Effect of urethan anesthesia on cigarette smoke-induced airway injury in guinea pigs

The effect of urethan anesthesia on cigarette smoke-induced airway responsiveness and permeability was studied in the guinea pig. Airway responsiveness was determined by measuring changes to airway resistance to graded doses of aerosolized histamine, and mucosal permeability was determined by measuring the appearance of fluorescein isothiocyanate-dextran (FITC-D) in the blood and examining its distribution in lung tissue after it had been delivered to the lung in an aerosol. The results confirm previous studies that smoke exposure increased airway responsiveness and mucosal permeability. They also show that urethan anesthesia administered before smoke exposure prevented the smoke-related changes in airway reactivity and mucosal permeability. In animals that remained conscious during the smoke exposure, there was increased deposition of the dextran in the regions of the bronchioloalveolar junctions with a more rapid uptake of FITC-D into the blood. We postulate that, when urethan anesthesia is administered before smoke exposure, the exudative phase of the inflammatory reaction produced by smoke exposure is suppressed.     

Airway hyperresponsiveness to bronchoconstrictor challenge after wood smoke exposure in guinea pigs.

Prior airway exposure to wood smoke induces an increase in airway responsiveness to subsequent smoke inhalation in guinea pigs (Life Sci. 63: 1513, 1998; 66: 971, 2000). To further characterize this airway hyperreactivity, we investigated and compared the airway responsiveness to bronchoconstrictor challenge before and 30 min after sham air exposure or wood smoke exposure in anesthetized and artificially ventilated guinea pigs. Various doses of substance P (0.8-6.4 microg/kg), capsaicin (0.2-3.2 microg/kg), prostaglandin F2alpha (30-3000 microg/kg), histamine (1-8 microg/kg), or acetylcholine (5-20 microg/kg) were intravenously injected at 2-min intervals in successively increasing doses to obtain the dose required to provoke a 200% increase in baseline total lung resistance (ED200). Wood smoke exposure significantly lowered the ED200 of substance P, capsaicin, and prostaglandin F2alpha whereas sham air exposure failed to do so. Furthermore, wood smoke exposure did not significantly alter the ED200 of histamine or acetylcholine. Pretreatment with phosphoramidon (2 mg/kg), an inhibitor of the neutral endopeptidase (the major degradation enzyme of substance P), before smoke exposure did not significantly affect the smoke-induced reduction in ED200 of substance P. Sectioning both cervical vagi before smoke exposure did not significantly alter the smoke-induced reduction in ED200 of capsaicin or prostaglandin F2alpha. These results suggest that airway exposure to wood smoke acutely produces airway hyperresponsiveness to substance P, capsaicin, and prostaglandin F2alpha, but not to histamine or acetylcholine. Since the combination of phosphoramidon and wood smoke exposure did not result in an additive potentiation of smoke-induced airway hyperresponsiveness to substance P, it is suggested that an inhibition of the degradation enzyme of substance P may contribute to this increase in airway reactivity. Furthermore, vagally-mediated bronchoconstriction does not play a vital role in enhanced airway responsiveness to capsaicin or prostaglandin F2alpha.     

Changes in lung mechanics and reactivity with age after viral bronchiolitis in beagle puppies

We measured changes with growth in lung function and airway reactivity after acute canine parainfluenza virus type 2 (CPI2, n = 5), canine adenovirus type 2 (CAV2, n = 7), and sequential CAV2-CPI2 (n = 6) infections or no infection (controls, n = 6) in beagle puppies (age approximately 79 days). In the CPI2 and CAV2 groups, a lower respiratory illness developed by day 3 postinfection with clinical recovery by day 14. In the CAV2-CPI2 group, puppies were inoculated initially with CAV2 and 12 days later with CPI2. In this group, illness persisted until day 14 after infection with CPI2. Lung resistance (RL), dynamic (Cdyn) and static (Cst) lung compliance, functional residual capacity (FRC), and responsiveness to aerosolized histamine were measured before infection and at periodic intervals until 239 +/- 43 days of age. Lung function data were analyzed using a longitudinal random effects model. In all groups, FRC, Cst, and Cdyn increased with age. In all infected groups, the regression slopes for Cdyn were steeper than in controls. RL decreased linearly with age without group slope differences. Histamine reactivity increased with age, but there were no differences in slope among groups. Lung pathological studies showed areas of obliterative bronchiolitis and chronic small airways inflammation particularly in the CAV2 and CAV2-CPI2 groups. Thus, viral bronchiolitis produces chronic small airways inflammation in beagle puppies and alters the changes in lung function occurring with growth. Histamine reactivity increases with age and is not modified by viral infection.     

Effects of granulocyte depletion on pulmonary responsiveness to aerosol histamine

The effects of granulocyte depletion with hydroxyurea on pulmonary responsiveness to aerosol histamine were studied in 10 chronically instrumented unanesthetized sheep. Sheep were studied when granulocyte counts were normal (B), after 3 days of hydroxyurea but before granulocyte counts had dropped below 700 cells/mm3 (H), and after granulocyte counts had fallen below 200 cells/mm3 (D). Hydroxyurea itself had no effect on aerosol histamine responsiveness and the results were unaffected by the order of experimentation. All 10 sheep were less responsive (P less than 0.05) to aerosol histamine when granulocyte depleted effective dose of histamine that caused a reduction to 65% of control dynamic compliance (ED65Cdyn = 23.98 +/- 4.70 mg/ml) compared with base line (ED65Cdyn = 7.06 +/- 1.86 mg/ml). Those sheep initially most responsive to aerosol histamine had the greatest attenuation in their airway responsiveness to aerosol histamine (P less than 0.05). There was a significant negative correlation between absolute granulocyte counts in peripheral blood and pulmonary responsiveness to aerosol histamine during base-line (B) condition (r = -0.74, P less than 0.05) and for the data as a whole [r = -0.69, P less than 0.05 (B + H + D)]. Circulating granulocytes and/or pulmonary inflammation may contribute to pulmonary responsiveness to bronchial challenge.     

Increased in vitro airway responsiveness in sheep following repeated exposure to antigen in vivo

We have studied the effect of repeated in vivo antigen exposure on in vitro airway responsiveness in sensitized sheep. Fourteen sheep underwent five biweekly exposures to aerosolized Ascaris suum antigen or saline. Following this exposure regimen, the animals were killed and tracheal smooth muscle and lung parenchymal strips were prepared for in vitro studies of isometric contraction in response to histamine, methacholine, prostaglandin F2 alpha, and a thromboxane A2 analogue. No alteration in tracheal smooth muscle responsiveness was observed between saline- and antigen-exposed tissue. In contrast, by use of lung parenchymal strips as an index of peripheral airway responsiveness, significant increases in responsiveness to histamine and a thromboxane A2 analogue (10(-6) and 10(-5) M) were observed in antigen-exposed tissue compared with saline controls. These results demonstrate that repeated antigen exposure in vivo selectively increase the responsiveness of peripheral lung smooth muscle to certain chemical mediators of anaphylaxis.     

Immunologic and nonimmunologic responsiveness in ragweed-sensitized dogs

The relationship between airway responsiveness to inhaled antigen and histamine, immunologic release of lung histamine, immunologic responsiveness of skin, and specific immunoglobulin E (IgE) antibodies were examined in 11 inbred allergic dogs immunized with extracts of ragweed and grass and 5 nonimmunized control dogs from the same colony. Airway responsiveness to antigen and histamine was characterized by the doses that increased the airflow resistance of the total respiratory system to twice the control values (ED200). Highly significant correlations were found between airway responsiveness and cutaneous responsiveness to antigen and other immunologic characteristics (e.g., IgE and histamine released from lung by inhaled antigen) in all dogs. In ragweed-sensitized dogs, there was an inverse correlation between immunologic responsiveness (reflected by the cutaneous response to antigen and histamine released from lung by inhaled antigen) and nonimmunologic responsiveness of airways (histamine ED200: r = 0.73, P less than 0.05 and r = 0.75, P less than 0.01, respectively). Antigen ED200 was also correlated with histamine release from lung after antigen inhalation (r = 0.74; P less than 0.01). We conclude that airway reactions to inhaled antigen in allergic dogs are dependent not only on immunologic factors but also on the degree of nonimmunologic airway responsiveness to histamine and that these factors are correlated inversely.     

Prostaglandin F2α increases responsiveness of pulmonary airways in dogs

We studied the effect of prostaglandin F_2α (PGF_2α) on the responsiveness of pulmonary airways in dogs. Airway responsiveness was assessed by determining the bronchoconstrictor response to increasing concentrations of acetylcholine aerosol delivered to the airways. In each of five dogs, we determined responsiveness during treatment with physiologic saline, histamine, or PGF_2α aerosols. The doses of histamine and PGF_2α were determined by establishing the largest dose of each which could be given to the dog without causing bronchoconstriction (subthreshold doses). We found that airway responsiveness was not significantly different during histamine treatment than after saline, however, responsiveness increased during treatment with PGF_2α. In addition, the hyperresponsiveness induced by PGF_2α was prevented by pretreatment with the ganglion blocking drug hexamethonium (5 mg/kg given intravenously). The results show that PGF_2α specifically increases the responsiveness of pulmonary airways in doses that do not cause bronchoncostriction, and suggest that the hyperresponsiveness involves a neural mechanism such as increased responsiveness of airway sensory nerves.     

Effect of tidal volume and anesthetic agent on airway responsiveness to histamine

Dose-response relationships for bronchoconstriction in response to aerosal histamine were assessed before and after vagotomy in 11 dogs anesthetized with barbiturates and in 9 dogs anesthetized with alpha-chloralose-urethan. The dose-response relationships following vagotomy were assessed during spontaneous ventilation and during muscular paralysis and mechanical ventilation with tidal volume (VT) similar to each animal's VT prior to vagotomy. After vagotomy the spontaneous VT of both groups increased but the VT of the alpha-chloralose-urethan group was significantly less than that of the barbiturate group. The histamine responsiveness of the animals anesthetized with barbiturates was significantly greater during mechanical ventilation when VT was reduced to prevagotomy levels compared with during spontaneous ventilation. In contrast, the histamine responsiveness of the alpha-chloralose-urethan group was not significantly changed by reducing VT to prevagotomy levels. In six other dogs anesthetized with pentobarbital sodium and studied after vagotomy, responsiveness to histamine aerosol during controlled ventilation with breaths of prevagotomy VT was greater than responsiveness during mechanical ventilation with large volume breaths given immediately afterward. Thus the magnitude of VT of dogs after vagotomy may influence airway responsiveness, and the influence of anesthetic agents on airway responsiveness after vagotomy may in part be due to their effects on VT. Furthermore, bronchodilation accompanying large volume ventilation persists after vagotomy, suggesting that it is not exclusively mediated by changes in parasympathetic activity.     

Chronic tobacco smoke exposure increases airway sensitivity to capsaicin in awake guinea pigs.

Tobacco smoke (TS) exposure induces airway hyperreactivity, particularly in sensitive individuals with asthma. However, the mechanism of this airway hyperreactivity is not well understood. To investigate the relative susceptibility of atopic and nonatopic individuals to TS-induced airway hyperreactivity, we exposed ovalbumin (OA)-sensitized and nonsensitized guinea pigs to TS exposure (5 mg/l air, 30-min exposure, 7 days/wk for 120-156 days). Two similar groups exposed to compressed air served as controls. Airway reactivity was assessed as an increase in enhanced pause (Penh) units using a plethysmograph that allowed free movement of the animals. After 90 days of exposure, airway reactivity increased in OA-TS guinea pigs challenged with capsaicin, bradykinin, and neurokinin A fragment 4--10 aerosols. In addition, substance P content increased in lung perfusate of OA-TS guinea pigs in response to acute TS challenge compared with that of the other groups. Airway hyperirritability was not enhanced by phosphoramidon but was attenuated by a cocktail of neurokinin antagonists, nor was airway hyperreactivity observed after either methacholine or histamine challenge in OA-TS guinea pigs. Chronic TS exposure enhanced neither airway reactivity to histamine or methacholine nor contractility of isolated tracheal rings. In conclusion, chronic TS exposure increased airway reactivity to capsaicin and bradykinin aerosol challenge, and OA-TS guinea pigs were most susceptible to airway dysfunction as the result of exposure to TS compared with the other groups. Increased airway reactivity to capsaicin suggests a mechanism involving neurogenic inflammation, such as increased activation of lung C fibers.     

Detection of mediator-induced airway constriction by barometric plethysmography in mice

The barometric method has recently been employed to detect airway constriction in small animals. This study was designed to evaluate the barometric method to detect mediator-induced central and peripheral airway constriction in BALB/c mice. First, the central airway constrictor carbachol and the peripheral airway constrictor histamine were employed to induce airway constriction, which was detected by both the conventional body plethysmography and the barometric method in anesthetized mice. Second, bronchoconstriction induced by aerosolized carbachol or other mediators was detected with the barometric plethysmography in conscious, unrestrained mice. Carbachol inhalation caused about four-fold increase in pulmonary resistance (RL) and about two-fold increase in enhanced pause (Penh) in anesthetized mice. In contrast, in the same preparation, histamine aerosol induced a decrease in dynamic compliance (Cdyn), with no alteration in RL or Penh. In awake mice, carbachol and methacholine caused increases in Penh, frequency, and tidal volume (VT). On the other hand, histamine, histamine + bradykinin, and prostaglandin-D2 did not alter Penh but decreased VT in conscious mice. These data suggest that there was no sufficient evidence to indicate that Penh could be a good indicator of bronchoconstriction for the whole airways.